Rapid Solution and Solid Phase Syntheses of Oligo(1,4-phenylene ethynylene)s with Thioester Termini: Molecular Scale Wires with Alligator Clips. Derivation of Iterative Reaction Efficiencies on a Polymer Support

1388

J . Org. Chem. 1997, 62, 1388-1410

Ra p id Solu tion a n d Solid P h a se Syn th eses of Oligo(1,4-p h en ylen e

eth yn ylen e)s w ith Th ioester Ter m in i: Molecu la r Sca le Wir es w ith

Alliga tor Clip s. Der iva tion of Iter a tive Rea ction Efficien cies on a

P olym er Su p p or t

LeRoy J ones, II, J effry S. Schumm, and J ames M. Tour*

Department of Chemistry and Biochemistry, University of South Carolina,

Columbia, South Carolina 29208

Received December 13, 1996^X

The syntheses of soluble oligo(2-alkyl-1,4-phenylene ethynylene)s via an iterative divergent/

convergent approach starting from 1-(diethyltriazyl)-3-alkyl-4-[(trimethylsilyl)ethynyl]benzenes are

described. When the solublizing alkyl group is an ethyl substituent, the monomer, dimer, tetramer,

and octamer can be synthesized. The octamer, however, is only minimally soluble. When the alkyl

substituent is 3-ethylheptyl or dodecyl, the compounds are easily dissolved even at the 16-mer

stage. The 16-mer is 128 Å long in its near-linear extended conformation. At each stage in the

iteration, the length of the framework doubles. Only three sets of reaction conditions are needed

for the entire iterative synthetic sequence: an iodination, a protodesilylation, and a Pd/Cu-catalyzed

cross coupling. Synthesis of the dodecyl-containing 16-mer was also achieved on Merrifield’s resin

using the iterative divergent/convergent approach. The oligomers were characterized spectroscopi-

cally and by mass spectrometry. The optical properties are presented which show that at the

octamer stage, the optical absorbance maximum is nearly saturated. The size exclusion chroma-

tography values for the number average weights, relative to polystyrene, illustrate the tremendous

differences in the hydrodynamic volume of these rigid rod oligomers verses the random coils of

polystyrene. These differences become quite apparent at the octamer stage. Equations were derived

for assessing the efficiency of the polymer-supported reactions based on resin weight differences,

molar concentration differences, and elemental analysis data. Each of these methods’ limitations

are discussed. Attachment of thiol end groups, protected as thioacetyl moieties, was achieved.

These serve as binding sites for adhesion to gold surfaces. In some cases, one end of the oligomeric

chains is capped with a thiol group so that the surface attachments to gold could be studied. In

other cases, thiol groups are affixed to both ends of the molecular chains so that future conduction

studies could be done between proximal metallic probes. The rigid rod conjugated oligomers may

act as molecular wires in molecular scale electronic devices, and they also serve as useful models

for understanding analogous bulk polymers.

In tr od u ction

theses and attachments of protected thiol moieties to one

or both ends of the phenylene ethynylenes are presented.

These thiols serve as molecular scale alligator clips for

adhesion of the molecular scale wires to the gold probes.^1,4

Additionally, synthesis of the dodecyl-containing 16-mer

was also achieved on Merrifield’s resin (chloromethyl

polystyrene) using the iterative divergent/convergent

approach; a method which significantly streamlined the

preparation.⁵

The expectation and potential of molecular-sized com-

putational devices has attracted the interest of the

synthetic chemist, and rapid synthetic architectural

approaches to these and related structures have been

dramatically increasing.¹Here we describe the synthetic

details for the formation of soluble oligo(2-alkyl-1,4-

phenylene ethynylene)s, potential molecular scale wires,

by a rapid iterative divergent/convergent doubling

approach.^1-3These 1,4-phenylene ethynylene compounds

exhibit even further rigidity (no main-chain conformers

that alter the molecular length) over the 2,5-thiophene

ethynylene compounds described previously.¹The syn-

Resu lts a n d Discu ssion

Mon om er Syn th eses for Solu tion -Ba sed Oligo-

m er iza t ion s. The syntheses of the monomers are

described in Scheme 1. Initially, we thought an ethyl

substituent would provide enough solubility for the

conjugated oligomers up to the 16-mer, the size necessary

for bridging patterned proximal gold probes.¹We there-

^XAbstract published in Advance ACS Abstracts, February 15, 1997.

(1) See the preceding article (Pearson, D.; Tour, J . M. J . Org. Chem.

1997, 62, xxx) and references therein for a description of molecular

scale electronics, the synthetic organic challenges involved, the efficacy

of the iterative divergent/convergent approach for the conjugated

structures via the coupling approaches chosen here, and the utility of

thiol end groups to act as alligator clips.

(4) Tour, J . M.; J ones, L., II; Pearson, D. L.; Lamba, J . S.; Burgin,

T.; Whitesides, G. W.; Allara, D. L.; Parikh, A. N.; Atre, S. J . Am. Chem.

Soc. 1995, 117, 9529. (b) Dhirani, A. A.; Zehner, R. W.; Hsung, R. P.;

Guyot-Sionnest, P., Sita, L. R. J . Am. Chem. Soc. 1996, 118, 3319. (c)

Bumm, L. A.; Arnold, J . J .; Cygan, M. T.; Dunbar, T. D.; Burgin, T. P.;

J ones, L., II, Allara, D. L.; Tour, J . M.; Weiss, P. S. Science 1996, 271,

1705.

(5) (a) Young, J . K.; Nelson, J . C.; Moore, J . S. J . Am. Chem. Soc.

1994, 116, 10841. (b) Bharathi, P.; Patel U.; Kawaguchi, T.; Pesak, D.

J .; Moore, J . S. Macromolecules 1995, 28, 5955. (c) Polymer-Supported

Reactions in Organic Synthesis; Hodge, P., Sherrington, D. C., Eds.;

Wiley: New York, 1980. (d) Nelson, J . C.; Young, J . K.; Moore, J . S. J .

Org. Chem. 1996, 61, 8160.

(2) Schumm, J . S.; Pearson, D. L.; Tour, J . M. Angew. Chem., Int.

Ed. Engl. 1994, 33, 1360.

(3) An iterative divergent/convergent approach has been used to

prepare the analogous oligo(1,3-phenylene ethynylenes): (a) Zhang,

J .; Moore, J . S.; Xu, Z. F.; Aguirre, R. A. J . Am. Chem. Soc. 1992, 114,

2273. (b) Xu, Z. F.; Moore, J . S. Angew. Chem., Int. Ed. Engl. 1993,

32, 1354. For related oligomers and polymers, see: (c) Grubbs, R. H.;

Kratz, D. Chem. Ber. 1993, 126, 149. (d) Scherf, U.; Mu¨llen, K.

Synthesis 1992, 23. For a recent review on the subject, see: (e) Tour,

J . M. Chem. Rev. 1996, 96, 537.

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1389

Sch em e 1

fore started with 3-nitroacetophenone and easily formed

the ethyl side chain by hydrogenation under acidic

conditions. N-Acetyl protection and Friedel-Crafts acy-

lation afforded a 4:1 mixture of the methyl ketones in

which the desired 4-acylation product predominated.²

However, tert-butoxycarbonyl (BOC) protection of the

amine and Friedel-Crafts acylation afforded only the

desired 4-acylation product 2. The BOC protecting group

was conveniently lost upon aqueous workup. Conversion

of the amine to the diethyltriazene 3 followed by one-pot

conversion of the methyl ketone to the (trimethylsilyl)-

alkyne⁶afforded the desired monomer 4 for the iterative

divergent/convergent oligomerization (Scheme 1, eq 1).

Notice that the triazyl moiety was quite robust and able

to survive the LDA treatment.

We subsequently discovered that the ethyl moiety did

not provide sufficient solubility (vide infra), thus we

prepared the analogous monomer bearing a 3-ethylheptyl

substituent (Scheme 1, eq 2). It was surmised that a

monomer bearing a stereogenic center would afford

diastereomers on successive dimerizations, thereby re-

tarding crystallization and increasing solubility. We

started with 3-nitrobenzoic acid and treated the corre-

sponding acid chloride 5 with the cyanocuprate to afford

the desired ketone 6. We tried numerous methods to

concomitantly reduce both the ketone and the nitro

moieties of 6; however, all methods failed, including the

Pd-C/H₂/HCl reduction that worked in the synthesis of

1. Therefore, the multistep reaction sequence was used

which involved reduction of the ketone to the alcohol,

acetoxy formation, and finally reduction under dissolving

metal conditions for both reductive removal of the acetoxy

(6) Negishi, E.; King, A. O.; Tour, J . M. Org. Synth. 1985, 64, 44.

1390 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

Sch em e 2

moiety and amine formation. Additionally, the standard

NaNO₂/HCl conditions that were used in eq 1 did not

permit diazonium formation on this more lipophilic

substrate; however, tert-BuONO permitted formation of

the intermediate diazonium species which was followed

by capture with diethylamine to form the triazene 8.⁷

Preparation of 9 then proceeded under the standard

alkynylation conditions (Scheme 1, eq 2).⁶

After discovering that the 3-ethylheptyl substituent in

9 permitted solubility through to the 16-mer (vide infra),

we desired to prepare an analogous version which would

permit formation of soluble homogeneous material. Hexa-

decyl chains often cause side chain crystallization in

polymers while dodecyl chains can impart solubility

without the crystallization difficulties.⁸Thus a dodecyne

moiety was affixed to 3-nitroiodobenzene, via a Pd/Cu-

catalyzed coupling,⁹followed by reduction and conversion

to the desired 13, again via exclusive 4-acylation of the

BOC-protected amine (Scheme 1, eq 3).

second portion to form 17. Bringing the two portions

back together in the presence of a soluble Pd/Cu catalyst

mixture⁹coupled the aryl iodide to the terminal alkyne,

thus generating the dimer 20. Since the dimer had the

same end groups as the monomer, the same process could

be repeated. Iteration of this reaction sequence doubled

the length of the dimer 20 to afford the tetramer 29 and

so on to the octamer 38. At that point, the octamer was

nearly insoluble, and we were only able to obtain a UV-

visible spectrum and a direct exposure mass spectrum

(MS). However, carrying out the same sequence starting

from 3-ethylhexyl or dodecyl bearing monomers 9 and

13, respectively, we were able to achieve the syntheses

of the 16-mers 45 and 46, respectively. The silylated

alkynes showed good oxidative stability; however, upon

protodesilylation, the tetramers and octamers were air

sensitive.

Mon om er Syn th eses for th e P olym er Su p p or ted

Ap p r oa ch . The monomers needed for the polymer

support synthesis were prepared as depicted in Scheme

3. Compound 11 was converted to the diazonium inter-

mediate which was captured with 2-(ethylamino)etha-

nol, to form the hydroxytriazene according to Moore’s

protocol.⁵Silylation to form 47 followed by acetyl conver-

sion to the silylalkyne afforded 48. Compound 48 was

divided into two portions; the first portion was desilylated

to form 49, the anchor unit to be attached to the polymer

support. The second portion was iodinated¹⁰to form the

iodoarene 16.

Oligom er Syn th eses in Solu tion . The solution

phase iterative divergent/convergent synthetic approach

is outlined in Scheme 2. The sequence involved, for

example, partitioning 4 into two portions, conversion of

the triazene in one portion to the aryl iodide 14 with

MeI,¹⁰and protodesilylation of the alkynyl end of the

(7) Doyle, M. P.; Bryker, W. J . J . Org. Chem. 1979, 44, 1572.

(8) Lamba, J . S. S.; Tour, J . M. J . Am. Chem. Soc. 1994, 116, 11723.

(9) (a) Suffert, J .; Ziessel, R. Tetrahedron Lett. 1991, 32, 757. (b)

Sonogashira, K; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 4467.

(c) Stephens, R. D.; Castro, C. E. J . Org. Chem. 1963, 28, 3313.

(10) Moore, J . S.; Weinstein, E. J .; Wu, Z. Y. Tetrahedron Lett. 1991,

32, 2465.

Oligom er Syn t h eses on t h e P olym er Su p p or t .

Attachment of 49 to the polymer support resin and the

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1391

Sch em e 3

oligomer syntheses on the polymer support are depicted

in Scheme 4. Etherification of Merrifield’s resin with an

excess of anchor 49 provided the polymer-supported

monomer 50. Unfortunately, it was difficult to determine

the etherification reaction completion point by IR analy-

sis (vide infra). Even though the reaction was allowed

to stir over several days at elevated temperature with a

3-fold excess of anchor 49, gel-phase ¹³C NMR¹¹on the

supported material revealed a small resonance at δ 46.77

corresponding to benzylic chloride residues. This was

further confirmed by elemental analysis. Fortunately,

it was found that the unreacted benzylic chloride sites

on the resin did not appear to hinder the oligomer

synthesis on the polymer support.

The successive dimerization sequence was pursued as

illustrated in Scheme 4. 50 was subjected to a Pd/Cu

cross-coupling⁹with monomer 16 to afford the polymer-

supported dimer 51. Two-thirds of 51 was then treated

with MeI, affording liberated dimer 25 in 86% yield over

two steps. The remaining one-third of the polymer-

supported dimer 51 underwent desilylation with tetra-

n-butylammonium fluoride (TBAF) to afford the polymer-

supported dimer 52. 52 was then treated with all of

the liberated iodide 25 under Pd/Cu cross coupling

conditions to afford the polymer-supported tetramer 53.

The sequence was repeated to generate the tetramer

34, octamer 42, and 16-mer 58 in the yields indicated

over three steps each. Remarkably, we found that the

liberated oligomers were contaminated with only small

amounts of impurities as assessed by chromatographic

and spectroscopic analyses. These impurities were easily

removed after passing the compounds through silica

gel.

was placed on a NaCl plate. After the beads were swollen

with 2-3 drops of CCl₄, a second NaCl plate was pressed

onto the beads, and an FTIR spectrum was recorded.

Absorptions at 3311 cm^-1(strong) and 2109 cm^-1(weak)

are characteristic of the terminal alkynyl carbon-

hydrogen and carbon-carbon stretches, respectively, and

an absorption at 2156 cm^-1(strong) is characteristic of

the carbon-carbon stretch of the trimethylsilyl-termi-

nated alkyne.^5,13As expected, we observed that the

coupling reaction was accompanied by the disappearance

of the 3311 cm^-1band and the appearance of the 2156

cm^-1absorption. In the reverse manner, the trimethyl-

silyl removal step was accompanied by the disappearance

of the 2156 cm^-1band and the appearance of the 3311

cm^-1band. Suitability of this monitoring technique was

confirmed by removal and characterization of the tri-

methylsilyl-protected product.⁵

Gel-phase ¹³C NMR spectra were also recorded on the

polymer-supported material at each step in the reaction

sequence. Again, the loss or gain of the trimethylsilyl

resonance at δ 0.3-0.5 was a diagnostic feature.

Assessin g Solid P h a se Rea ction Yield s. Though

reaction progress was monitored by IR, and gel-phase

NMR, these spectroscopic tools are of relatively low

sensitivity when used for resin analysis. Yield estimation

by these methods was difficult, especially for the longer

oligomers. For these reasons, the approaches used for

the calculation of yield are described.

The yield can be determined based on the weight

difference of the resin.¹⁴The weight increase caused by

chemical modification of the resin (∆W) is related to the

yield (Y) by the following relation:

Y ) ∆W/N_si∆M

(4)

Sp ectr oscop ic Rea ction Mon itor in g Tech n iqu es

on th e Resin . Since the aforementioned reactions were

conducted on an insoluble support, conventional tech-

niques such as TLC could not be used to monitor the

progress of the reactions. Consequently, completion of

each reaction was estimated by infrared analysis of the

polymer bound substrate.^5,12Polymer-supported material

where N_siis the moles of starting functionality in 1 g of

initial resin, and ∆M is the change in molecular weight

upon reaction. If mass is lost over the course of the

reaction, both ∆W and ∆M should be negative. The

results of these calculations for the formation of com-

pounds 50-58 are given in Table 1. Unfortunately, the

yields determined by this method were found to be

(11) Crowley, J . I.; Rapoport, H. Acc. Chem. Res. 1976, 9, 135. (b)

Leznoff, C. C. Chem. Soc. Rev. 1974, 3, 65. (c) Leznoff, C. C. Acc. Chem.

Res. 1978, 11, 327. (d) Dewitt, S. H.; Czarnik, A. W.; Ellman, J . A.

Acc. Chem. Res. 1996, 29, 114. (e) Giralt, E.; Rizo, J .; Pedroso, E.

Tetrahedron 1984, 40, 4141.

(13) Grindley, T. B.; J ohnson, D. F.; Katritzky, A. R.; Keogh, H. J .;

Thirkettle, C.; Topsom, R. D. J . Chem. Soc., Perkin Trans. 2 1974, 3,

282.

(12) Yan, B; Kumaravel, G; Anjaria, H; Wu, A; Petter, R. C.; J ewell,

C. F., J r.; Wareing, J . R. J . Org. Chem. 1995, 60, 5736.

(14) An analogous equation utilizing resin weight differences has

been derived by Moore. See reference 5d.

1392 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

Sch em e 4

unreliable. Small mechanical mass losses naturally oc-

curred during resin manipulations. Small mass in-

creases due to residual solvent or impurities trapped in

the polymer matrix were also observed. These small

mass changes had an enormous effect on the calculated

product yields since the weight changes due to the coup-

ling or deprotection reactions were small relative to the

weight of the initial resin. These errors were exacerbated

when the weight change due to the reaction was small

(for example, in a protodesilylation step), or when

performing the reactions on a small scale. As a result,

weight changes were only used as a rough guide to the

success of a reaction.

The molar concentrations of the products in the final

resins were also monitored for compounds 50-58. The

molar concentration decreases as the resin’s mass in-

creases due to modification of the reactive moiety. The

actual concentration (mol/g) of the product in the final

resin (N_pf) is given by

N_pf) YN_si/W_f) N_siY/(1 + ∆W) ) YN_si/(1 +

YN_si∆M) (5)

where W_fis the weight of the final resin.

The theoretical concentration (mol/g) of product in the

final resin is

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1393

Ta ble 1. Da ta for P olym er ic Su p p or t Rea ction s Der ived Usin g Gr a vim etr ic An a lysis

theor wt change,

actual wt

% yield by

theor product concn,

exptl product concn,

compound

∆W_theor(g)

increase, ∆W (g)

wt diff, Y

N_pf(theor) (mmol/g)

N_pf(mmol/g)

50

51

52

53

54

55

56

57

17.41

12.25

-0.84

5.47

-0.20

2.56

17.95

9.98

-0.78

4.43

-0.08

1.71

0.03

103

81

103

93

0.61

0.51

0.52

0.40

0.41

0.28

0.29

0.17

0.61

0.42

0.45

0.33

48

0.34^b

0.21^b

0.07^b

168

-

-0.04

0.98

0.23

37^a

a

b

Yield was calculated over two steps. Based on quantitative yield for the deprotection step and the average two-step yield for the

coupled product.

N_pf(theor) ) N_si/1 + N_si∆M

(6)

E ) N_piM_e(N_e/N_p)/(1 + ∆W/W_i)

(10)

Rearrangement of this expression and substitution into

eq 4 gives

The theoretical and experimentally determined values

for N_pfare listed in Table 1. In both cases the concentra-

tion of 50 in the final resin was determined via elemental

analysis using a method that will be described later. This

initial value of 0.61 mmol/g was then used as the basis

for the remainder of the calculations. The errors of the

weight measurement caused significant discrepancies in

the calculated concentrations. As a result, the moles of

reagent needed in the polymer-supported reactions were

determined assuming quantitative yields for all previous

steps other than the formation of 50.

Y ) (N_p/N_e)(E/M_eN_si) (1+ ∆W/W_i)

(11)

Substituting the expression for ∆W (eq 4) into eq 8 gives

the derivation of the yield from the elemental analysis.

Y ) (N_p/N_e)(E/M_eN_si)(1 + YN_si∆M/W_i) )

1/[(N_e/N_p)(M_eN_si/E) - N_si∆M] (12)

The yield of these reactions was also derived from the

elemental analysis data. The calculations assumed that

no side reactions were taking place and that unreacted

functionality did not participate in any subsequent

reactions. The element used for the calculations was

unique either to the moiety being added to the resin or

to the starting functionalized resin. Three distinct

situations were encountered which required different

methods of yield determination: (1) The tag element was

added to the resin over the course of the reaction. (2)

The tag element was removed from the resin. (3) The

tag element was unique to the resin and present before

and after the reaction. The derivation of the equations

used for each case are outlined here.

The yield for the formation of 50 based on the elemen-

tal analysis for N was

Y ) 1/[3(14.0 g/mol)(0.001 mol/g)/0.0256] -

(0.001 mol/g)(349 g/mol) ) 0.77 ) 77%

The moles per gram of Merrifield’s resin has a reported

error of (0.05 mmoles. The error in the nitrogen

determination is estimated to be (0.2%. Therefore, an

approximate expression for the error (e) in Y based on

elemental analysis for nitrogen is

e ) (5 × 10^-5mol/1.00 × 10^-3mol) +

(0.002/wt fraction N) ) (0.13

Case 1: When the tag element is added to the resin

during the course of the reaction the yield (Y) is given

by

This relatively high error is largely due to the low

weight percent of nitrogen present in the final resin.

Nevertheless, this method proved to be the most accurate

for calculating the molar concentration of 50 on the

polymer support. Calculation of the chloride concentra-

tion of Merrifield’s resin by elemental analysis has a

higher error than the titration method used by the

manufacturer.

Y ) (N_pi/N_si)

(7)

where N_piis the moles of product relative to 1 g of the

initial resin, and N_siis again the moles of starting

functionality in 1 g of the initial resin. Elemental

analysis yields the weight fraction of the tag element (E).

E is the weight in grams of an element (W_e) relative to

the weight in grams of the final resin (W_f). Since the

element is unique to the product, this can then be related

to the moles of product in 1 g of the final resin (N_pf) by

Case 2: When the tag element is removed during the

course of the reaction the yield is given by

Y ) 1 - (N*_si/N_si)

(13)

where N*_siis the moles of unreacted starting functional-

ity in the final resin relative to 1 g of starting resin.

Because the tag element is unique to the unreacted resin,

the weight fraction is now

E ) W_e/W_f) N_pfM_e(N_e/N_p)

(8)

where M_eis the molecular weight of the tag element in

g/mol, N_eis the moles of the tag element, and N_pis the

moles of product. N_pfis related to N_piby

E ) W_e/W_f) N_sfM_e(N_e/N_p)

(14)

N_pf) N_p/W_p) N_p/(W_i+ ∆W) ) N_pi/(1 + ∆W/W_i) (9)

where N_sfis the moles of starting functionality present

in 1 g of final resin. N*_siis related to N_sfby

where W_fis the weight in grams of the final resin, W_pis

the weight in grams of the product, and W_iis the weight

in grams of the initial resin. With this relationship in

hand, E can be expressed in terms of N_pi.

N_sf) N*_si/(1 + ∆W/W_i)

(15)

E can then be expressed in terms of N*_si.

1394 J . Org. Chem., Vol. 62, No. 5, 1997

E ) N*_siM_e(N_e/N_s)/(1 + ∆W/W_i)

J ones et al.

(by MeI treatment) recovered from the resin after each

coupling step. The formula used for these determinations

was

(16)

where N_sis the moles of starting functionality. Rear-

rangement of this expression and substitution into eq 13

gives

Y ) N_p/N_s) N_pW_i/N_si

(22)

Y ) 1 - [(N_s/N_e)(E/M_eN_si)(1+ ∆W/W_i)]

(17)

The value of 0.61 mmol/g, determined from elemental

analysis, was used for the concentration of 50 in the poly-

mer matrix. From that point onward, the yields were

calculated over three steps. The moles of products were

determined directly from purified compounds after cleav-

age from the resin. Subsequent to 50, N_sifor the initial

polymer-supported compound of the three-step sequence

was determined using eq 6. Using this method the yields

of the cleaved dimer 25, tetramer 34, octamer 42, and

16-mer 58 were 86%, 77%, 80%, and 79%, respectively.

This corresponds to an average yield of 92-93% over the

deprotection, coupling, and cleavage steps. The amount

of material that remained uncleaved by the MeI treat-

ment is not known, but the error in the nitrogen analysis

excludes the possibility of this aiding in the determina-

tion.

In summary, the determination of the coupling ef-

ficiency on the polymer support has severe difficulties

due to the fact that the resin comprises the vast majority

of the materials’ mass. Though the absolute error

remains constant, the percent error increases at each

iteration along the sequence. Therefore, yield determi-

nations based on elemental composition changes along

a series of steps eventually have such significant errors

that the assessment becomes completely unreliable.

However, if the initial linker’s coupling efficiency is

reasonably established, the yield determinations over the

three-step sequence can be sufficiently utilized.

Ch a r a cter iza tion of th e Oligom er s. As mentioned

above, while the ethyl-containing octamer 38 was nearly

insoluble, the longer alkyl-bearing octamers 39 and 40,

as well as the corresponding 16-mers 45 and 46, were

quite soluble, and they could be adequately spectroscopi-

cally characterized. While many of the lower molecular

weight oligomers could be characterized by direct expo-

sure via electron impact MS, in order to obtain MS data

on the soluble octamer 39 and 16-mer 45, it was neces-

sary to use matrix-assisted laser desorption/ionization

mass spectrometry (MALDI-MS) using a sinapinic acid

matrix, positive ion mode. The dodecyl-containing oc-

tamer 40 and 16-mer 46 were simpler to characterize

spectroscopically than the 3-ethylheptyl-containing oli-

gomers since the former are not mixtures of diastereo-

mers. However, 40 and 46, being more lipophilic than

39 and 45, were too insoluble in the polar MALDI-MS

matrices, thus no MS data could be obtained. FAB-MS

did not work on these samples, presumably due to

charging difficulties. The 16-mers are 128 Å long as

determined by a conformational minimization using MM2

with extended π-Hu¨ckel and multiconformational pa-

rameters.¹⁵This length is long enough to span the gaps

between proximal patterned electronic probes.¹

Substituting the expression for ∆W (eq 4) into eq 14

gives the calculation of the yield from element loss based

on elemental analysis. Taking advantage of the ratio of

tag element to product, (N_p/N_e) ) (N_s/N_e) ) 1 (for mono-

substituted tag element on resin), the expression for

calculating the yield becomes

Y ) 1 - (N_p/N_e)(E/M_eN_si)(1+ YN_si∆M/W_i) )

1 - [(N_p/N_e)(E/M_eN_si)]

(18)

[∆M(N_p/N_e)E/M_eN_e] + 1

The yield for the formation of 50 based on loss of Cl is

1 - [1(0.0061)/(35.45 g/mol)(0.001 mol/g)]

1(349 g/mol)(0.0061)/(35.45 g/mol) + 1

0.78 ) 78%

Y )

)

This yield is in good agreement with that based on

analysis for nitrogen. The error for this measurement

is estimated at (0.29.

Case 3: If the tag element is unique to the resin but

is not lost on reaction, the moles of the element are no

longer directly related to the amount of product formed.

The change in the elements’ weight fraction is entirely

due to the weight change of the resin. The weight change

of the resin can be related to the change in the weight

fraction of the tag element by

∆E ) E_f- E_i) (W_ef/W_f) - (W_ei/W_i) )

W_ef/(W_i+ ∆W) - W_ei/W_i(19)

Recognizing that W_ei) W_ef, and expressing in terms

of 1 g of initial resin, therefore E_i) W_ei, and eq 19

simplifies to

1

∆E )

- 1 W_ei

(20)

[

(

)

]

1 + ∆W

Substituting eq 4 for ∆W and rearrangement gives the

yield expressed in terms of weight fraction of the tag

element before and after the reaction.

1

- 1

(

)

1 + (∆E/E_i)

N_si∆M

Y )

(21)

The yield of the formation of 51 is then

{1/[1 + (-0.0025/0.0256)]} - 1

(0.00061 mol/g) (341 g/mol)

Y )

) 0.52 ) 52%

Absorption (Figure 1) and emission studies (Figure 2)

were conducted on the oligomers. As expected, we

The estimated error for this measurement is (0.92.

The error was higher than the calculated value for all

the compounds prepared. Clearly, the accuracy of this

method is unacceptable for yield determination at the low

nitrogen levels present in these systems.

Due to the inherent inaccuracies of yield determination

based on elemental and gravimetric analysis, yields were

also calculated based on the amount of cleaved product

(15) Oligomer lengths were simulated using standard molecular

modeling procedures. All calculations were performed on a Power

Macintosh 8100/80 AV using Personal CAChe version 3.7 for both

structure drawing and minimization. The CAChe mechanics ap-

plication implements a standard MM2 force field. All energy cal-

culations were minimized over

a large number of iterations to

convergence at local minima nearest in energy to the starting

compounds’ energies.

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1395

F igu r e 4. The values of M_ndetermined by SEC (relative to

polystyrene standards in THF) versus the actual molecular

weights for the triazene-terminated oligomers 9, 21, 30, 39,

and 45 (circles) and the iodide-terminated oligomers 25, 34,

42, and 58 (squares).

F igu r e 1. The UV-vis absorbance spectra (THF) of the

monomer through 16-mer iodides, 16, 25, 34, 42, and 58,

respectively.

Sch em e 5

F igu r e 2. The fluorescence emission spectra (THF) of the

dimer through 16-mer iodides, 25, 34, 42, and 58, respectively.

As illustrated in Figure 3, we also noticed that the

π-extended triazene substituents shifted the absorption

maxima bathochromically, relative to the corresponding

iodides, for the monomers through octamers. However,

the saturation effects are apparent at the 16-mer stage

since the two absorptions are nearly identical (Figure 3).

The results of the size exclusion chromatography

(SEC), which is commonly used in the separation and

identification of oligomers, are shown in Figure 4. SEC

is not a direct measure of MW, but a measure of the

hydrodynamic volume. Thus, the number average mo-

lecular weight (M_n) values of the rigid rod oligomers

should be significantly inflated relative to the randomly

coiled polystyrene standards. As expected, the M_nvalues

of the monomer 9 (M_n) 390, actual MW ) 400), dimer

21 (M_n) 715, actual MW ) 626), dimer 25 (M_n) 900,

actual MW) 736), tetramer 30 (M_n) 1335, actual MW

) 1079), and tetramer 34 (M_n) 1705, actual MW) 1274)

were reasonably close to the actual MWs (initial slope =

1.0 in Figure 4), prior to significant polystyrene coiling.

However, the M_nvalues of the octamer 39 (M_n) 2,790,

actual MW) 1981), octamer 42 (M_n) 3625, actual MW)

2348), 16-mer 45 (M_n) 6650, actual MW) 3789), and

16-mer 58 (M_n) 8856, actual MW) 4495) were much

greater than the actual MWs. As expected, these curves

in Figure 4 are quite similar in their appearance to the

curves generated from related thiopheneethynylene oli-

gomers of similar molecular weights.¹

F igu r e 3. The optical absorbance maxima (λ_max) versus the

number of repeat units (n) in the triazene-terminated oligo-

mers 9, 21, 30, 39, and 45 (circles) and the iodide-terminated

oligomers 16, 25, 34, 42, and 58 (squares).

observed an increase in the absorption maxima from

shorter wavelength (263 nm) for the monomer 16 to

longer wavelength (377 nm) for the 16-mer 58. Likewise,

an increase in the emission intensity from shorter

wavelength (359 nm) for the dimer 25 to longer wave-

length (414 nm) for the 16-mer 58 was observed (Figure

2). The monomer 16 did not fluoresce. Note that a near

saturation of the systems appears to have occurred by

the octamer stage so that doubling the conjugation length

from the octamer to the 16-mer caused only a small

bathochromic shift in absorption and emission maxima.

Atta ch m en t of Th iol En d Gr ou p s. With the req-

uisite precisely defined oligo(phenylene ethynylene)s in

1396 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

Sch em e 6

Sch em e 7

hand, we then addressed methods to affix protected thiols

to the ends of the oligomers. The thiols serve as molec-

ular alligator clips for adhesion to gold probe surfaces.^1,4

We recently used these thiol-terminated oligo(phenylene

ethynylene)s to record electronic conduction through

single undoped conjugated molecules that were end-

bound onto a metal probe surface.^4cThese nearly linear

molecules worked quite well for single molecule inser-

tions into self-assembled monolayers of dodecane thiolate

on gold, thereby providing a means of molecular isolation.^4c

Monothiol-terminated systems were prepared for adhe-

sion of these oligomers to single gold surfaces, and in

other cases, R,ω-difunctionalized systems were prepared

for adhesion between proximal gold surfaces. Though the

aromatic thiols could be synthesized under reductive base

conditions, due to their oxidative instabilities, they

proved difficult to use in actual surface deposition experi-

ments. However, the acetyl-protected thiols were resil-

ient enough for manipulations in air, yet they could be

readily hydrolyzed with NH₄OH in the presence of the

gold probe surfaces.^1,4

arene 60 can be coupled to the aryl iodide end (tail) of

the oligomers. Of course, our oligomers would permit

orthogonal end group functionalization, for example, one

end containing a thiol moiety for adhesion to gold and

the other end a carboxy moiety for adhesion to an oxide.

However, for all of our initial studies on difunctionalized

systems, proximal gold connects were considered, thus

identical end groups sufficed.

Scheme 5 shows the efficient attachment of 59 to the

heads of both phenylacetylene and the dimeric system

62. Scheme 6 shows an approach to a concomitant head

and tail functionalization of the ethyl-containing mono-

mer, dimer, and tetramer. Deprotection of the thiols was

accomplished with NaOH under reductive conditions to

minimize disulfide formation. Though this deprotection

method proved effective for laboratory isolation and

characterization of the thiols, it could not be used for

molecular scale electronics study since exogenous metals

such as zinc or Na⁺would interfere with electronic

measurements.⁴Thus we developed the complementary

in situ technique using NH₄OH.⁴

Using a convergent method of molecular alligator clip

formation and attachment, the two thioesters 59 and 60

were synthesized.¹The aryl iodide 59 can be coupled to

Both ends of the oligomers could be functionalized as

shown in Scheme 6. However, the R,ω-bis-terminal

alkynes 68-70 showed increasingly low yields in the

couplings with 59. Therefore, we used a stepwise pro-

cedure (Scheme 7) of tail functionalization, followed by

protodesilylation, to afford 80-82. The use of TBAF

alone for the desilylation reactions also caused deacyla-

tion of sulfur; however, the buffered TBAF/HF conditions

the alkynyl end (head) of the oligomers while the alkynyl

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1397

wt fraction z ) 0.0100

worked well. Finally, coupling with 59 permitted forma-

tion of the R,ω-dithioesters 83 and 84.

wt fraction y )

(0.001 mol y × 152.63 g/mol)/1 g resin ) 0.1526

Su m m a r y

wt fraction x ) 1.000 - (0.1526 + 0.0100) ) 0.8374

We outlined the rapid syntheses of oligo(2-alkyl-1,4-

phenylene ethynylene)s via an iterative divergent/

convergent approach that needed only three sets of

reaction conditions for the entire iterative synthetic

sequence: an iodination, a protodesilylation, and a Pd/

Cu-catalyzed cross coupling. The syntheses were con-

ducted in solution and on a polymer support. At each

stage in the iteration, the length of the framework

doubled. Equations were derived for assessing the ef-

ficiency of the polymer-supported reactions based on resin

weight differences, molar concentration differences, and

elemental analysis data. Each of these methods had

severe limitations. Attachment of the complementary

thiol end groups, protected as thioester moieties, was

achieved. These serve as binding units for adhesion to

gold surfaces, and these rigid rod conjugated oligomers

have been shown to exhibit single molecule conductivity.⁴

This represents a step in the development of organic

architectures for molecular scale electronic instruments.¹

The percentages of the elements present in each unit were

the following: x: C: 92.24%, H: 7.76%; y: C: 70.82%, H: 5.96%,

Cl: 23.23%; z: C: 90.83%, 9.17%.

The percentage of a given element in the resin was then

the sum of the weight fractions of each unit multiplied by the

percentage of the element in each unit. Therefore, the per-

centage of each element in Merrifield’s resin was:

%C ) (%C in x)(wt fraction x) +

(%C in y)(wt fraction y) + (%C in z)(wt fraction z) )

(92.24%)(0.8374) + (70.82%)(0.1526) +

(90.83%)(0.0100) ) 88.96%

%H ) (%H in x)(wt fraction x) +

(%H in y)(wt fraction y) + (%H in z)(wt fraction z) )

(7.76%)(0.8374) + (5.96%)(0.1526) +

(9.17%)(0.0100) ) 7.50%

% Cl ) (% Cl in y)(wt fraction y) )

(23.23%)(0.1526) ) 3.54%

Exp er im en ta l P r oced u r es

Ca lcu la tion of Elem en ta l P er cen ta ges for th e F u n c-

tion a lized Resin s. The percentage of each element in the

functionalized resins was determined in a manner analogous

to that used for Merrifield’s resin. Calculations were per-

formed based on a 77% yield for the formation of 50 on

the polymer support. For compounds 50-57, the resin was

treated as a mixture of x, y, z and the functionalized unit

(y′). The relative percentages of y and y′ were assigned as

23% and 77% respectively, based on the yield derived

from analysis for nitrogen. The formation of 51-57 was

assumed to be quantitative. Sequential modification of

the initial y unit caused a change in the relative percentages

of the monomer units comprising the resin. The weight

increase for 1 g of Merrifield’s resin caused by the modification

was:

Gen er a l. The general instrumental methods and proce-

dures used have been described previously.¹Merrifield’s resin

was purchased from Aldrich. The tert-butyl nitrite diazonium

formations,⁷methyl ketone to (trimethylsilyl)alkyne conver-

sions,⁶Pd/Cu-catalyzed aryl halide-terminal alkyne cou-

plings,⁹triazene formation and iodinations,^3a,b,7,10and the

protodesilylation reactions¹⁶were conducted according to

reported procedures. Terminal alkynes beyond the dimer

stage were often oxidatively unstable, and they were used

immediately after preparation; thus spectroscopic character-

ization was minimized. The 3-ethylheptyl-containing oligo-

mers could not be characterized by ¹³C NMR due to the

existence of multiple diastereomers. FTIR characterization

of the polymer-supported reactions were carried out by placing

ca. 10 mg of the polymer-supported material on a NaCl plate.

After the beads were swollen with 2-3 drops of CCl₄, a second

NaCl plate was pressed onto the beads, and an FTIR spectrum

was recorded.⁵Gel-phase ¹³C NMR spectra on the polymer-

supported material were recorded at 125 MHz on a Bru¨ker

AM-500 spectrometer. The NMR gel samples were prepared

as follows:¹⁷polymers were dried under vacuum at 60 °C until

constant weight was obtained. 300 mg were weighed into a

10 mm NMR tube and CDCl₃was added. Complete swelling

of the polymers was normally achieved by allowing them to

equilibrate with the solvent for 15-30 min. Sometimes,

ultrasonic agitation (Bransonic 5200) was necessary to obtain

well-dispersed samples. The syntheses of 59 and 60 have been

described previously.¹Unless otherwise noted, all compounds

were >95% pure as judged by NMR, GC, or combustion

analyses. The oligomers’ puritites can be assessed by their

polydispersity indexes M_w/M_n.

wt increase for 1 g of Merrifield’s resin )

[(molecular wt of y′) - (molecular wt of y)]

(mol y in 1 g of Merrifield’s resin)

Using 50 as an example:

) [(501.8 g/mol) - (152.6 g/mol)](0.001 mol × 0.77) )

0.269 g

The weight fraction of each unit was then:

wt fraction styrene (x) +

wt fraction 4-vinylbenzyl chloride (y) +

wt fraction functionalized 4-vinylbenzyl

chloride (y′) + wt fraction divinylbenzene (z) ) 1.00

Again using 50 as an example:

Ca lcu la tion of Elem en ta l P er cen ta ges for Mer r ifield ’s

Resin . Merrifield’s resin is a copolymer of styrene (x),

4-vinylbenzyl chloride (y), and divinylbenzene (z). The com-

mercial resin was listed to contain 1% w/w divinylbenzene and

1.00 ( 0.05 mequiv/g of 4-vinylbenzyl chloride. Thus, the

weight fraction of each unit can be determined as follows:

wt fraction z ) 0.0100 g z/1.269 g resin ) 0.0079

wt fraction y )

(0.001 mol y × 0.23 × 152.6 g/mol) ) 0.0351

wt fraction y′ ) (0.001 mol y′ × 0.77 ×

501.8 g/mol)/1.269 g resin ) 0.3045

wt fraction styrene (x) +

wt fraction 4-vinylbenzyl chloride (y) +

wt fraction divinylbenzene (z) ) 1.00

wt fraction x ) 0.8374 g x/1.269 g resin ) 0.6599

(16) (a) Bengton, G.; Keyaniyan, S.; Demeijere, A. Chem. Ber. 1986,

119, 3607. (b) Hurst, D. T.; McInnes, A. G. Can. J . Chem. 1965, 43,

2004. (c) Gaffney, B. L.; J ones, R. A. Tetrahedron Lett. 1982, 23, 2257.

(17) Giralt, E.; Rizo, J .; Pedroso, E. Tetrahedron 1984, 40, 4141.

1398 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

The percentage of each element could then be determined

as before.

1455.7, 1358.4, 1336.8, 1293.8, 1256.0, 1186.6, 1145.7, 1059.7,

1017.8, 954.0, 874.6, 857.6, 821.8, 585.7, 583.8, 547.8 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.59 (d, J ) 7.9 Hz, 1 H), 6.46

(s, 1 H), 6.44-6.42 (m, 1 H), 4.15 (s, 2 H), 2.89 (q, J ) 7.4 Hz,

2 H), 2.47 (s, 3 H), 1.15 (t, J ) 7.4 Hz, 3 H). ¹³C NMR (75

MHz, CDCl₃) δ 199.0, 150.3, 148.5, 133.4, 126.5, 116.1, 111.0,

29.0, 28.0, 15.6. HRMS calcd for C₁₀H₁₃NO: 163.0997.

Found: 163.0992.

%C ) (%C in x)(wt fraction x) + (%C in y)

(wt fraction y) + (%C in y′)(wt fraction y′) + (%C in z)

(wt fraction z) ) (92.24%)(0.6599) + (70.82%)(0.0351) +

(78.98%)(0.3045) + (90.83%)(0.0079) ) 88.12%

4-(Dieth yltr ia zen yl)-2-eth yla cetop h en on e (3).²To 2

(12.60 g, 77.3 mmol) in water (316 mL) and hydrochloric acid

(53 mL) was added sodium nitrite (5.48 g, 79.42 mmol) in

water (10 mL) at 0 °C. The reaction was stirred at 0 °C for 30

min and then poured into water (530 mL), potassium carbon-

ate (84 g), and diethylamine (63 mL) at 0 °C. The reaction

was stirred for 30 min at 0 °C and then poured into water.

The aqueous layer was extracted with diethyl ether (3 × 25

mL), the organic layer was dried over magnesium sulfate, and

the product was concentrated in vacuo to afford 17.90 g (94%)

%H ) (%H in x)(wt fraction x) + (%H in y)

(wt fraction y) + (%H in y′)(wt fraction y′) + (%H in z)

(wt fraction z) ) (7.76%)(0.6599) + (5.96%)(0.0351) +

(6.64%)(0.3045) + (9.17%)(0.0079) ) 7.42%

%N ) (%N in y′)(wt fraction y′) )

(8.37%)(0.3045) ) 2.55%

% Cl ) (% Cl in y)(wt fraction y) )

(23.23%)(0.0351) ) 0.82%

of the title compound as a dark brown liquid. IR (neat) 2975,

-1

2935, 2873, 1680, 1597, 1556, 1243, 1109, 952 cm

.

¹H NMR

(500 MHz, CDCl₃) δ 7.68 (d, J ) 8.2 Hz, 1 H), 7.29-7.25 (m,

2 H), 3.77 (q, J ) 7.2 Hz, 4 H), 2.93 (q, J ) 7.4 Hz, 2 H), 1.27

(br t, 6 H), 1.22 (t, J ) 7.5 Hz, 3 H). ¹³C NMR δ 201.1, 154.1,

146.9, 133.8, 131.6, 123.1, 117.4, 30.0, 28.1, 16.2. HRMS calcd

for C₁₄H₂₁N₃O: 247.1685. Found: 247.1687.

3-Eth yla n ilin e.²Anhydrous ethanol (100 mL), 3-nitroac-

etophenone (16.52 g, 100 mmol), concentrated hydrochloric

acid (20.0 mL), and 10% palladium on carbon (2 g) were placed

in a Parr flask. The flask was purged with hydrogen before

pressurizing to 60 psi and heating to 70 °C. The pressure was

maintained overnight. The palladium on carbon was then

filtered and the reaction mixture poured into 3 M sodium

hydroxide (200 mL). The solution was extracted with ether

(3×) and the combined organic layers were washed with brine

and dried over magnesium sulfate. The magnesium sulfate

was filtered and the solvent removed in vacuo to afford 12.29

g of the title compound as a brown oil which was taken on to

the next step with no further purification. R_f) 0.14 (9:1;

hexane:ether). ¹H NMR (500 MHz, CDCl₃) δ 7.08 (t, J ) 7.7

Hz, 1 H), 6.62 (d, J ) 7.1 Hz, 1 H), 6.54 (s, 1 H), 6.53-6.51

(m, 1 H), 3.55 (br s, 2 H), 2.56 (q, J ) 7.6 Hz, 2 H), 1.21 (t, J

) 7.6 Hz, 3 H). HRMS calcd for C₈H₁₁N: 121.0891. Found:

121.0888.

1-(Dieth yltr iazen yl)-3-eth yl-4-[(tr im eth ylsilyl)eth yn yl]-

ben zen e (4).²To a stirred solution of diisopropylamine (9.4

mL, 67 mmol) in THF (70 mL) was added at 0 °C under

nitrogen n-butyllithium (40.6 mL, 65 mmol, 1.6 M in hexanes).

The reaction mixture was stirred at 0 °C for 5 min and then

cooled to -78 °C. To the LDA solution was added 3 (15.5 g,

62.8 mmol) in THF (40 mL). The reaction mixture was stirred

at -78 °C for 1 h before adding, at the same temperature,

diethyl chlorophosphate (9.1 mL, 63 mmol). The reaction

mixture was allowed to warm to room temperature and stirred

for 3 h. The reaction solution was then transferred via cannula

into 2.25 equiv of LDA [made as above with diisopropylamine

(19.6 mL, 140 mmol) and n-butyllithium (88.3 mL, 141.3 mmol)

in THF (150 mL)] at -78 °C. The ensuing reaction mixture

was stirred at -78 °C for 30 min and then allowed to warm to

room temperature overnight at which time the reaction was

cooled to 0 °C and chlorotrimethylsilane (8.2 mL, 65 mmol)

was added. The solution was poured into water (100 mL) and

extracted with ether. The combined ether extracts were

washed with brine and dried over magnesium sulfate. Filtra-

tion and removal of the solvent in vacuo left a brown oil which,

upon purification by flash chromatography on silica gel (5:1;

hexane:ethyl acetate), afforded 10.81 g (57%) of the title

compound as a clear, colorless oil. IR (neat) 3290, 2105, 1585,

3-Eth yl-N-(ter t-bu toxyca r bon yl)a n ilin e (1). To a solu-

tion of crude 3-ethylaniline (7) (100 mmol) and di-tert-butyl

dicarbonate (34.50 g, 150 mmol) in THF (300 mL) was added

1 M sodium hydroxide (300 mL) in three portions. The

reaction was heated to reflux for 2 h and cooled to room

temperature. The reaction was poured into water and the

organic layer extracted with ether (3×). The organic layer was

dried over magnesium sulfate, filtered, and concentrated in

vacuo. The crude mixture was purified by flash chromatog-

raphy on silica gel (9:1; hexane:ether) to afford 21.12 g (96%)

of the title compound as a yellow oil. R_f) 0.39 (9:1; hexane:

ether). IR (neat) 3332, 2971, 2932, 2875, 1704, 1610, 1534,

1492, 1441, 1368, 1309, 1247, 1162, 1054, 986, 871, 774, 738,

1482, 1390, 1090, 1065, 1005, 820, 620 cm^-1

.

¹H NMR (300

MHz, CDCl₃) δ 7.36 (d, J ) 8.2 Hz, 1 H), 7.23 (d, J ) 1.7 Hz,

1 H), 7.16 (dd, J ) 8.2, 2.1 Hz, 1 H), 3.74 (q, J ) 7.2 Hz, 4 H),

2.78 (q, J ) 7.5 Hz, 2 H), 1.24 (t, J ) 7.2 Hz, 9 H), 0.23 (s, 9

H). ¹³C NMR (75 MHz, CDCl₃) δ 151.4, 147.6, 133.1, 120.3,

118.6, 117.5, 104.7, 97.2, 28.0, 14.7, 0.18. HRMS calcd for

C₁₇H₂₇N₃Si: 301.1974. Found: 301.1983.

721, 697 cm^-^{1 1}H NMR (300 MHz, CDCl₃) δ 7.19 (d, J ) 7.8

.

Hz, 1 H), 7.15 (s, 1 H), 7.10 (d, J ) 8.1 Hz), 6.86 (d, J ) 7.4 1

H), 6.42 (br s, 1 H), 2.62 (q, J ) 7.6 Hz, 2 H), 1.50 (s, 9 H),

1.21 (t, J ) 7.6 Hz, 3 H). ¹³C NMR (75 MHz, CDCl₃) δ 153.0,

145.3, 138.4, 128.9, 122.6, 118.1, 116.0, 80.3, 29.0, 28.4, 15.6.

HRMS calcd for C₁₃H₁₉NO₂: 221.1416. Found: 221.1420.

2-Eth yl-1-iod oh exa n e.²To dichloromethane (150 mL) in

a 500 mL oven-dried vessel equipped with a condenser was

added sequentially triphenylphosphine (15.7 g, 60 mmol),

imidazole (4.1 g, 60 mmol), and iodine (15.2 g, 60 mmol). The

mixture was stirred until the iodine had dissolved and a

reddish-yellow solid appeared. To the mixture was added

dropwise 2-ethyl-1-hexanol (7.8 mL, 50 mmol), keeping the

temperature of the reaction just below reflux. After addition

of the alcohol was complete, the reaction was stirred for 2 h

and monitored by gas chromatography. The completed reac-

tion was concentrated in vacuo, and silica gel (10 g) was added

to the resulting crude mixture in hexane (100 mL). The

mixture was stirred for 15 min and filtered through a plug of

silica gel. The resulting clear solution was concentrated in

vacuo to afford the title compound in nearly quantitative yield.

4-Am in o-2-eth yla cetop h en on e (2).²To a 250 mL three-

neck round-bottomed flask equipped with a reflux condenser

and drying tube containing aluminum chloride (4.93 g, 37

mmol) and carbon disulfide (50 mL) at 0 °C were added 1 (2.32

g, 10.5 mmol) in carbon disulfide (50 mL) and acetyl chloride

(1.49 mL, 21 mmol). The reaction mixture was heated to reflux

at 70 °C overnight. After cooling to 60 °C the reflux condenser

was removed to allow the carbon disulfide layer to boil off

before pouring it into ice-water (10 mL). The solution was

then poured into 3 M potassium hydroxide (100 mL) and

extracted with ether (5×). The combined organic extracts were

washed with brine and dried over magnesium sulfate. The

solution was filtered, and the solvent was removed in vacuo

to give a brown oil that was purified by flash chromatography

on silica gel (2:1; hexane:ether) to afford 0.82 g (48%) of the

title compound as a dark brown liquid which solidified upon

standing. R_f) 0.27 (2:1; hexane:ether). Mp 53-55 °C. IR

(KBr) 3456.5, 3347.7, 3218.7, 2966.0, 1635.2, 1601.8, 1553.6,

IR (neat) 2960, 2928, 2858, 1458, 1187 cm^-1

.

¹H NMR (500

MHz, CDCl₃) δ 3.25 (2 sets of overlapping dd, J ) 14.1, 9.0

Hz, 2 H), 1.4-1.1.0 (m, 9 H), 0.88 (t, J ) 6.5 Hz, 3 H), 0.84 (t,

J ) 7.4 Hz, 3 H). ¹³C NMR (125 MHz, CDCl₃) δ 40.7, 34.1,

29.2, 27.4, 23.2, 16.5, 14.5, 11.3.

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1399

3-Nitr oben zoyl Ch lor id e (5).²To an oven-dried vessel

were added 3-nitrobenzoic acid (83.56 g, 500 mmol) and

benzene (1 L). The vessel was fitted with a reflux condenser

and drying tube. To the reaction was added oxalyl chloride

(65.4 mL, 750 mmol) at room temperature. After seeing no

reaction after a period of 10 min, 1 drop of N,N-dimethylfor-

mamide was added. Stirring was continued until evolution

of hydrogen chloride and carbon monoxide was complete. The

reaction was concentrated in vacuo, and calcium hydride (2

g) and benzene (200 mL) were added. Stirring was continued

for 1 h at which time the reaction was filtered through Celite

and concentrated in vacuo to afford 92.3 g (99%) of the title

compound as a brown solid. ¹H NMR (300 MHz, CDCl₃) δ 8.94,

(t, J ) 2.0 Hz, 1 H), 8.53 (ddd, J ) 8.2, 2.3, 1.0 Hz, 1 H), 8.42

(ddd, J ) 7.9, 1.8, 1.2 Hz, 1 H), 7.75 (t, J ) 8.0 Hz, 1 H).

1-(3′-Nitr op h en yl)-3-eth ylh ep ta n e-1-on e (6).²To tert-

butyllithium (37.4 mL, 80 mmol, 2.14 M in hexane) in ether

(20 mL) was added 2-ethyl-1-iodohexane (9.6 g, 40 mmol) at

-78 °C. The reaction mixture was stirred for 30 min and then

added to flame-dried zinc chloride (7.6 g, 56 mmol) in THF

(30 mL) at room temperature. The resulting cloudy solution

was stirred for 30 min. In a separate vessel was combined

tetrakis(triphenylphosphine)palladium(0) (0.7 g, 0.6 mmol) and

3-nitrobenzoyl chloride (5.57 g, 30 mmol) in THF (10 mL), and

the vessel was flushed with nitrogen. To the resulting Pd(0)

solution was then added the zinc reagent at room temperature.

The reaction was stirred at room temperature overnight and

then poured into water. The aqueous layer was extracted with

ethyl acetate and dried over magnesium sulfate. The organic

layer was filtered and concentrated in vacuo. The crude

product was filtered and purified by flash chromatography on

silica gel (5:1; hexane:ethyl acetate) to afford 1.8 g (39%) of

the title compound as a clear yellow oil. IR (neat) 3086, 2929,

200 mmol) was added dropwise in THF (400 mL) at -78 °C

over 30 min. The reaction was stirred at -33 °C for 1 h and

quenched by the slow addition of ethanol. The crude mixture

was subjected to aqueous workup and the organic layer

extracted with ethyl acetate (4 × 50 mL). The organic layer

was dried over magnesium sulfate and purified by flash

chromatography on silica gel (5:1, hexane:ethyl acetate) to

afford 26.1 g (60 % yield) of the title compound as a light brown

oil. IR (neat) 3450, 3370, 2926, 1621, 1462, 1392, 1166 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.05 (t, J ) 8.0 Hz, 1 H), 6.57 (d,

J ) 8.0 Hz, 1 H), 6.51 (s, 1 H), 6.49 (d, J ) 7.7 Hz, 1 H), 3.58

(br s, 2 H), 2.47 (2 sets of overlapping ddd, J ) 16.6, 5.7, 5.5

Hz, 2 H), 1.57-1.43 (m, 2 H), 1.33-1.22 (m, 9 H), 0.9-0.82

(m, 6 H). ¹³C NMR (75 MHz, CDCl₃) δ 146.4, 144.7, 129.2,

118.8, 115.3, 112.5, 38.7, 35.1, 33.2, 32.7, 28.9, 25.8, 23.2, 14.2,

10.8.

1-(3′-Am in o-N-[(ter t-bu toxyca r bon yl)p h en yl]-3-eth yl-

h ep ta n e (7).²To a solution of 1-(3′-aminophenyl)-3-ethyl-

heptane (1.1 g, 5 mmol) and di-tert-butyl dicarbonate (1.5 mL,

6.5 mmol) in THF (15 mL) was added 1 N sodium hydroxide

(15 mL) in three portions. The reaction was heated to reflux

for 2 h and cooled to room temperature. The reaction was

poured into water and the organic layer extracted with ethyl

acetate. The organic layer was dried over magnesium sulfate,

filtered, and concentrated in vacuo. The crude mixture was

purified by flash chromatography on silica gel (6:1; hexane:

ethyl acetate) to afford 1.39 g (87%) of the title compound as

a brown oil. IR (neat) 3336, 2928, 1704, 1594, 1531, 1442,

1367, 1237, 1164, 1055 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ

7.19 (s, 1 H), 7.15 (d, J ) 7.3 Hz, 1 H), 7.12 (2 line m, 1 H),

6.84 (d, J ) 7.2 Hz, 1 H), 6.40 (br s, 1 H), 2.53 (2 sets of

overlapping ddd, J ) 17.1, 6.0, 5.1 Hz, 2 H), 1.53-1.49 (m, 1

H), 1.50 (s, 9 H), 1.32-1.22 (m, 10 H), 0.88 (t, J ) 6.3 Hz, 3

H), 0.84 (t, J ) 7.7 Hz, 3 H). ¹³C NMR (75 MHz, CDCl₃) δ

152.8, 144.4, 138.3, 128.8, 123.1, 118.5, 115.8, 80.3, 39.3, 38.7,

35.2, 33.3, 32.7, 28.9, 28.4, 25.7, 23.2, 14.2, 10.8.

2873, 1694, 1614, 1538, 1351 cm^-1

.

¹H NMR (300 MHz, CDCl₃)

δ 8.75 (t, J ) 0.8 Hz, 1 H), 8.40 (dt, J ) 7.7, 0.8 Hz, 1 H), 8.26

(dt, J ) 7.7, 0.8 Hz, 1 H), 7.66 (t, J ) 7.7 Hz, 1 H), 2.90 (d, J

) 6.6 Hz, 2 H), 2.03 (m, 1 H), 1.41-1.23 (m, 8 H), 0.88 (t, J )

7.2 Hz, 3 H), 0.85 (t, J ) 7.4 Hz, 3 H). ¹³C NMR (75 MHz,

CDCl₃) δ 198.3, 138.7, 133.6, 129.9, 127.1, 124.5, 123.0, 43.2,

35.6, 33.2, 28.9, 26.5, 22.9, 14.0, 10.9.

4-Am in o-2-(3′-eth ylh ep tyl)a cetop h en on e.²To a 25 mL

three-neck round-bottomed flask equipped with

a reflux

condenser and drying tube containing aluminum chloride (0.93

g, 7.0 mmol) and carbon disulfide (10 mL) at 0 °C were added

7 (0.64 g, 2.0 mmol) in carbon disulfide (10 mL) and acetyl

chloride (0.28 mL, 4.0 mmol). The reaction mixture was

heated to reflux at 70 °C for 3 h. After cooling to 60 °C, the

reflux condenser was removed to allow the carbon disulfide

layer to boil off before pouring it into ice-water (20 mL). The

solution was then poured into 3 N sodium hydroxide (20 mL)

and extracted with ether. The combined organic extracts were

washed with brine and dried over magnesium sulfate. The

solution was filtered and the solvent removed in vacuo to give

a brown oil that was purified by flash chromatography on

silica gel (3:1; hexane:ethyl acetate) to afford 0.36 g (70%) of

the title compound as a dark liquid. IR (neat) 3500, 3362,

1-(3′-Nitr op h en yl)-3-eth ylh ep ta n -1-ol.²To a suspension

of sodium borohydride (1.89 g, 50 mmol) in ethanol (100 mL)

at 0 °C was added 6 (26.3 g, 100 mmol) in ethanol (25 mL),

and the reaction was stirred at 0 °C for 1 h. The reaction was

quenched by the slow addition of 3 N hydrochloric acid at 0

°C, and the organic layer was extracted with ethyl acetate.

The crude product was purified by flash chromatography on

silica gel (7:1; hexane:ethyl acetate) to afford 17.88 g (67%) of

the title compound as a brown oil. IR (neat) 3418, 2923, 1538,

1348, 1065, 807, 739, 691 cm^-^{1 1}H NMR (300 MHz, CDCl₃) δ

.

8.21 (t, J ) 2.0 Hz, 1 H), 8.10 (dd, J ) 7.9, 2.1 Hz, 1 H), 7.67

(dd, J ) 8.4, 0.9 Hz, 1 H), 7.50 (t, J ) 7.9 Hz, 1 H), 4.87 (td,

J ) 8.4, 4.2 Hz, 1 H), 1.90 (d, J ) 3.6 Hz, 1 H), 1.78-1.69 (m,

1 H), 1.61-1.22 (m, 9 H), 0.90-0.81 (m, 6 H).

2926, 1601, 1455, 1252, 1141, 1054 cm^-1

.

¹H NMR (300 MHz,

CDCl₃) δ 7.59 (d, J ) 9.1 Hz, 1 H), 6.47 (s, 1 H), 6.45 (d, J )

9.9 Hz, 1 H), 3.96 (br s, 2 H), 2.86-2.80 (4 line m, 2 H), 2.49

(s, 3 H), 1.47-1.43 (m, 2 H), 1.39-1.22 (m, 9 H), 0.88 (t, J )

1-(3′-Nitr op h en yl)-1-a cetoxy-3-eth ylh ep ta n e.²To a so-

lution of 4-(N,N-dimethylamino)pyridine (0.16 g, 1.3 mmol) and

1-(3′-nitrophenyl)-3-ethylheptan-1-ol (36.02 g, 135.9 mmol) in

pyridine (150 mL) at 0 °C was added acetic anhydride (18.9

mL, 200 mmol) dropwise over 10 min. The reaction was stirred

for 30 min and monitored by TLC. The reaction was poured

into cold 3 N hydrochloric acid, and the organic layer extracted

with ethyl acetate. The organic layer was dried over magne-

sium sulfate, filtered, and concentrated in vacuo to afford 40.49

g (97%) of the title compound as a brown oil. No purification

7.5 Hz, 3 H), 0.86 (t, J ) 7.5 Hz, 3 H).

¹³C NMR (75 MHz,

CDCl₃) δ 199.23, 150.05, 148.11, 133.55, 127.58, 117.25, 111.39,

39.75, 35.69, 33.15, 32.76, 29.41, 29.39, 26.15, 23.53, 14.58,

11.24.

4-(Dieth yltr iazen yl)-2-(3′-eth ylh eptyl)acetoph en on e (8).²

To an oven-dried vessel containing boron trifluoride etherate

(0.37 mL, 3.0 mmol) at 0 °C was added 4-amino-2-(3′-ethyl-

heptyl)acetophenone (0.52 g, 2.0 mmol) in dichloromethane (2

mL) followed by tert-butyl nitrite (0.3 mL, 2.5 mmol). The

reaction was stirred for 30 min at 0 °C, and potassium

carbonate (1 g) and diethylamine (1 mL) were added sequen-

tially. The reaction was stirred for 1 h and poured into water.

The organic layer was extracted with ethyl acetate and dried

over magnesium sulfate. The sample was concentrated in

vacuo to afford 0.65 g (95%) of the title compound as a dark

was necessary. IR (neat) 2926, 1746, 1538, 1463, 1351, 1232,

-1

1023 cm

.

¹H NMR (300 MHz, CDCl₃) δ 8.19 (s, 1 H), 8.13

(d, J ) 7.1 Hz, 1 H). 7.62 (d, J ) 7.7 Hz, 1 H), 7.50 (t, J ) 8.0

Hz, 1 H), 5.83 (2 overlapping d, J ) 8.9, 8.9 Hz, 1 H), 2.07 (s,

3 H), 1.97-1.82 (m, 1 H), 1.65-1.57 (m, 2 H), 1.44-1.16 (m, 8

H), 0.89-0.79 (m, 6 H).

1-(3′-Am in op h en yl)-3-eth ylh ep ta n e.²To a 1 L oven-

dried round-bottomed flask equipped with a dry ice condenser

was condensed liquid ammonia (400 mL), and then lithium

metal (13.9 g, 2 mequiv) was added in small portions over 30

min. The resulting blue solution was stirred at -33 °C for 30

min and 1-(3′-nitrophenyl)-1-acetoxy-3-ethylheptane (61.4 g,

liquid. IR (neat) 2929, 1677, 1352, 1240, 1107 cm^-1

.

¹H NMR

(300 MHz, CDCl₃) δ 7.66 (d, J ) 8.8 Hz, 1 H), 7.25 (2 line m,

2 H), 3.77 (q, J ) 7.1 Hz, 4 H), 3.02-3.00 (4 line m, 1 H), 2.88-

2.82 (4 line m, 1 H), 2.55 (s, 3 H), 1.55 (br s, 1 H), 1.46-1.15

(m, 16 H), 0.95-0.82 (m, 6 H).

1400 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

1-(Dieth yltr ia zen yl)-3-(3′-eth ylh ep tyl)-4-[(tr im eth ylsi-

lyl)eth yn yl]ben zen e (9).²To a stirred solution of diisopro-

pylamine (1.8 mL, 13 mmol) in THF (15 mL) was added at 0

°C, under nitrogen, n-butyllithium (8.1 mL, 12 mmol, 1.49 M

in hexanes). The reaction mixture was stirred at 0 °C for 5

min and then cooled to -78 °C. To the LDA solution was

added 8 (3.71 g, 10.8 mmol) in THF (2 mL). The reaction

mixture was stirred at -78 °C for 1 h before adding, at the

same temperature, diethyl chlorophosphonate (1.7 mL, 12

mmol). The reaction mixture was allowed to warm to room

temperature and then stirred for 3 h. The reaction solution

was then transferred via cannula into 2.25 equiv of LDA [made

as above with diisopropylamine (3.1 mL, 22 mmol) and

n-butyllithium (16.3 mL, 24.3 mmol)] in THF (25 mL) at -78

°C. The ensuing reaction mixture was stirred at -78 °C for

30 min and then allowed to warm to room temperature for 1

h, at which time the reaction was cooled to 0 °C and chloro-

trimethylsilane (1.4 mL, 11 mmol) was added. The reaction

was stirred for 2 h at room temperature, and the solution was

poured into water (20 mL) and extracted with ether. The

combined ether extracts were washed with brine and dried

over magnesium sulfate. Filtration and removal of the solvent

in vacuo left a brown oil which upon purification by flash

chromatography on silica gel (9:1; hexane:ethyl acetate) af-

forded 1.9 g (43%) of the title compound as a yellow oil. IR

into a tan solid. R_f) 0.63 (4:1; hexane:ethyl acetate). IR

(neat) 3464, 3379, 3036, 2925, 2854, 1620, 1590, 1494, 1461,

1265, 1167, 909, 738 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.04

.

(dt, J ) 7.4, 0.90 Hz, 1 H), 6.57 (d, J ) 7.7 Hz, 1 H), 6.49 (d,

J ) 7.5 Hz, 1 H), 6.48 (d, J ) 7.3 Hz, 1 H), 3.57 (s, 2 H), 2.49

(t, J ) 7.9 Hz, 2 H), 1.56 (p, J ) 7.3 Hz, 2 H) 1.28-1.24 (m, 18

H), 0.87 (t, J ) 7.0 Hz, 3 H).). ¹³C NMR (100 MHz, CDCl₃) δ

146.51, 144.22, 129.18, 118.86, 115.40, 112.67, 36.19, 32.14,

31.60, 29.91, 29.87, 29.84, 29.78, 29.62, 29.59, 22.89, 14.28.

HRMS calcd for C₁₈H₃₁N: 261.2456. Found: 261.2448.

1-[N -(t er t -B u t o x y c a r b o n y l)a m in o ]-3-d o d e c y lb e n -

zen e. To a solution of 3-dodecylaniline (10) (119.84 g, 459

mmol) and di-tert-butyl dicarbonate (116 mL, 505 mmol) in

THF (500 mL) was added 1 M sodium hydroxide (500 mL) in

three portions. The reaction mixture was heated to reflux

overnight and then cooled to room temperature. The reaction

mixture was poured into water and the organic layer extracted

with ether (3×). The organic layer was dried over magnesium

sulfate, filtered, and concentrated in vacuo. The crude mixture

was purified by flash liquid chromatography on silica gel (24:

1; hexane:ether) to afford 163.86 g (99%) of the title compound

as a light brown oil which solidified upon standing. R_f) 0.41

(24:1; hexane:ether). IR (neat) 3320, 3145, 2920, 2853, 2356,

1

1693, 1597, 1539, 1440, 1366, 1251, 1162, 1054, 873 cm^-1. H

NMR (500 MHz, CDCl₃) δ 7.21 (br s, 1 H), 7.16 (t, J ) 7.9 Hz,

1 H), 7.10 (d, J ) 8.1 Hz, 1 H), 6.83 (d, J ) 7.5 Hz, 1 H), 6.41

(br s, 1 H), 3.55 (t, J ) 7.6 Hz, 2 H), 1.58 (p, J ) 7.3 Hz, 2 H),

1.50 (s, 9 H), 1.28-1.23 (m, 18 H), 0.89 (t, J ) 6.9 Hz, 3 H).

¹³C NMR (125 MHz, CDCl₃) δ 153.20, 144.42, 138.64, 129.13,

123.57, 118.90, 116.21, 80.73, 36.44, 32.31, 31.84, 30.06, 30.05,

30.02, 29.98, 29.90, 29.77, 29.74, 28.75, 23.07, 14.49. HRMS

calcd for C₂₃H₃₉NO₂: 361.2981. Found: 361.2993.

(neat) 2959, 2148, 1598, 1402, 1248, 1103, 843, 759 cm^-1

.

¹H

NMR (500 MHz, CDCl₃) δ 7.36 (d, J ) 8.2 Hz, 1 H), 7.21 (s, 1

H), 7.16 (d, J ) 8.2 Hz, 1 H), 3.74 (q, J ) 7.1 Hz, 4 H), 2.78

(m, 2 H), 1.63 (m, 1 H), 1.30-1.17 (m, 16 H), 0.95-0.81 (m, 6

H), 0.23 (s, 9 H). LRMS calcd for C₂₃H₄₁N₃Si: 399. Found:

399. λ_max(CH₂Cl₂) ) 334 nm. UV 10% edge value ) 388 nm.

M_n) 390, M_w) 417, M_w/M_n) 1.07.

Gen er a l P r oced u r e for th e Cou p lin g of a Ter m in a l

Alk yn e w ith a n Ar yl Ha lid e. Before beginning the reaction,

all of the starting materials were thoroughly flushed with

argon and/or nitrogen. To a stirring solution of the aryl halide,

bis(dibenzylideneacetone)palladium(0) (2 mol %), triphenylphos-

phine (2.5 equiv based on Pd(0)), and copper(I) iodide (2 mol

%) in THF was added the terminal alkyne followed by the

amine (4 equiv based on aryl halide) at room temperature

(unless otherwise stated) under argon and/or nitrogen in a

screw cap tube. The vessel was flushed with argon and/or

nitrogen, sealed, and allowed to stir overnight. The reaction

mixture was then subjected to an aqueous workup and the

aqueous layer extracted with ether, dichloromethane, or ethyl

acetate (3×). After drying the combined organic layers over

magnesium sulfate, the solvent was removed in vacuo to afford

a crude product which was purified by column chromatography

(silica gel). Eluents and other slight modifications are de-

scribed below for each reaction.

4-Am in o-2-d od ecyla cetop h en on e (11). To a two-neck

round-bottomed flask equipped with a reflux condenser con-

taining aluminum chloride (23.48 g, 176.10 mmol) and chlo-

robenzene (50 mL) at 0 °C was added 1-[N-(tert-butoxycarbonyl)-

amino]-3-dodecylbenzene (18.15 g, 50.30 mmol) in chlorobenzene

(50 mL) and acetyl chloride (3.93 mL, 55.3 mmol). The

reaction mixture was heated to reflux overnight and then

allowed to cool to room temperature. The solution was then

slowly poured into 3 M potassium hydroxide (100 mL) and

extracted with ether (3×). The combined organic extracts were

washed with brine and dried over magnesium sulfate. The

solution was filtered and the solvent removed in vacuo to give

a brown oil that was purified by gravity liquid chromatography

on silica gel (1:1; hexane:ether) to afford 12.90 g (85%) of the

title compound as a brown liquid which solidified upon

standing. R_f) 0.37 (1:1; hexane:ether). IR (neat) 3484, 3369,

3228, 3051, 2957, 2926, 2855, 1660, 1622, 1602, 1563, 1460,

1356, 1252, 1143, 909, 814, 738 cm^-1

.

¹H NMR (400 MHz,

3-(1′-Dod ecyn yl)n it r ob en zen e. 1-Iodo-3-nitrobenzene

(12.45 g, 50 mmol), 1-dodecyne (11.76 mL, 55 mmol), bis-

(dibenzylideneacetone)palladium(0) (0.57 g, 1.0 mmol), tri-

phenylphosphine (0.66 g, 2.50 mmol), copper(I) iodide (0.19 g,

1.0 mmol), N,N-diisopropylethylamine (35 mL, 200 mmol), and

THF (50 mL) afforded 14.21 g (99%) of the title compound as

a light brown oil after gravity liquid chromatography (9:1;

hexane:ether). R_f) 0.76 (9:1; hexane:ether). IR (neat) 3084,

2921, 2855, 2229, 1959, 1902, 1825, 1795, 1728, 1572, 1534,

CDCl₃) δ 7.61 (d, J ) 9.1 Hz, 1 H), 6.48-6.44 (m, 2 H), 3.96

(br s, 2 H), 2.85 (t, J ) 7.7 Hz, 2 H), 2.49 (s, 3 H), 1.50 (p, J )

7.7 Hz, 2 H), 1.40-1.23 (m, 18 H), 0.86 (t, J ) 7.0 Hz, 3 H).

¹³C NMR (100 MHz, CDCl₃) δ 198.78, 150.46, 147.23, 133.44,

126.30, 116.76, 110.96, 35.17, 31.98, 31.62, 31.61, 30.03, 29.79

(2 C), 29.73, 29.70, 29.43, 28.87, 22.74, 22.68, 14.15. HRMS

calcd for C₂₀H₃₃NO: 303.2562. Found: 303.2568.

4-(Dieth yltr iazen yl)-2-dodecyl-1-acetoph en on e (12). To

an oven-dried vessel containing boron trifluoride etherate (0.21

mL, 1.68 mmol) at 0 °C was added 11 (0.26 g, 0.86 mmol) in

dichloromethane (2 mL) followed by tert-butyl nitrite (0.17 mL,

1.4 mmol). The mixture was stirred for 30 min at 0 °C, and

potassium carbonate (0.56 g) and diethylamine (0.56 mL) were

sequentially added. The reaction was stirred for 2 h and

poured into water. The organic layer was extracted with ethyl

acetate and dried over magnesium sulfate. The sample was

concentrated in vacuo, and the crude oil that was purified by

flash liquid chromatography (9:1; hexane:ether) to afford 0.33

g (99%) of the title compound as a light brown oil. R_f) 0.36

(9:1; hexane:ether). IR (neat) 2927, 2855, 1677, 1597, 1559,

1467, 1351, 1301, 1165, 1096, 900, 805, 736, 675 cm^-1

.

¹H

NMR (400 MHz, CDCl₃) δ 8.21 (s, 1 H), 8.10 (ddd, J ) 8.3,

2.2, 1.0 Hz, 1 H), 7.65 (d, J ) 7.7 Hz, 1 H), 7.43 (t, J ) 8.1 Hz,

1 H), 7.24 (s, 1 H), 2.40 (t, J ) 7.1 Hz, 2 H), 1.60 (p, J ) 7.0

Hz, 2 H), 1.43 (p, J ) 7.0 Hz, 2 H), 1.28-1.25 (m, 12 H), 0.86

(t, J ) 7.1 Hz, 3 H). ¹³C NMR (100 MHz, CDCl₃) δ 148.01,

137.22, 129.04, 126.26, 125.94, 122.10, 93.58, 78.46, 31.90,

29.59, 29.52, 29.32, 29.14, 28.93, 28.47, 22.68, 19.33, 14.06.

HRMS calcd for C₁₈H₂₅NO₂: 287.1885. Found: 287.1891.

3-Dod ecyla n ilin e (10). Anhydrous ethanol (50 mL), 3-(1′-

dodecynyl)nitrobenzene (14.21 g, 49.51 mmol) and 10% pal-

ladium on carbon (2.50 g) were placed in a Parr flask. The

flask was purged with hydrogen before pressurizing to 65 psi

and heating to 65 °C. The pressure was maintained at 65 psi

for 5 h. The palladium on carbon was then filtered and the

solvent removed in vacuo to afford 12.54 g (97%) of the title

compound as a brown liquid which solidified upon standing

1449, 1431, 1395, 1348, 1239, 1105, 952, 893, 824 cm^-1

.

¹H

NMR (400 MHz, CDCl₃) δ 7.62 (d, J ) 8.3 Hz, 1 H), 7.26 (d, J

) 1.9 Hz, 1 H), 7.23 (dd, J ) 8.3, 2.0 Hz, 1 H), 3.72 (q, J ) 7.2

Hz, 4 H), 2.88 (t, J ) 7.8 Hz, 2 H), 2.50 (s, 3 H), 1.59 (p, J )

8.3 Hz, 2 H), 1.40-1.22 (m, 24 H), 0.86 (t, J ) 7.0 Hz, 3 H).

¹³C NMR (125 MHz, CDCl₃) δ 200.76, 153.83, 145.51, 133.98,

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1401

131.47, 123.85, 117.38, 35.05, 32.31, 32.17, 30.29, 30.09, 30.07,

30.06, 30.04, 29.95, 29.88, 29.74, 23.07, 14.49. HRMS calcd

for C₂₄H₄₁N₃O: 387.3250. Found: 387.3254.

ether, dichloromethane, or ethyl acetate (3×). After drying

the combined organic layers over magnesium sulfate, the

solvent was removed in vacuo. The crude product was then

purified by column chromatography (silica gel), yielding the

free alkyne which was immediately taken onto the next step.

Eluents and other slight modifications are described below for

each material.

1-(Dieth yltr ia zen yl)-3-d od ecyl-4-[(tr im eth ylsilyl)eth y-

n yl]ben zen e (13). To a stirred solution of diisopropylamine

(0.79 mL, 6.05 mmol) in THF (5 mL) was added at -78 °C,

under nitrogen, n-butyllithium (3.59 mL, 5.50 mmol, 1.53 M

in hexanes). The reaction mixture was allowed to warm to 0

°C for 10 min and then cooled to -78 °C. To the LDA solution

was added 12 (1.94 g, 5.00 mmol) in THF (5 mL). The reaction

mixture was stirred at -78 °C for 1 h before adding, at the

same temperature, diethyl chlorophosphonate (0.73 mL, 5.05

mmol). The reaction mixture was allowed to warm to room

temperature over 30 min before being recooled to -78 °C. The

reaction solution was then transferred via cannula into 2.25

equiv of LDA [made as above with diisopropylamine (1.62 mL,

12.38 mmol) and n-butyllithium (7.35 mL, 11.25 mmol, 1.53

M in hexane)] in THF (15 mL) at -78 °C. The ensuing

reaction mixture was allowed to warm to 0 °C over 30 min

and then recooled to -78 °C before chlorotrimethylsilane (1.59

mL, 12.5 mmol) was added. The solution was allowed to stir

overnight at room temperature before being poured into water

and extracted with ether (3×). The combined ether extracts

were washed with brine and dried over magnesium sulfate.

Filtration and removal of the solvent in vacuo left a brown oil

which, upon purification by gravity liquid chromatography on

silica gel (100:1; hexane:ether), afforded 1.17 g (53%) of the

title compound as a light brown oil. R_f) 0.64 (9:1; hexane:

ether). IR (neat) 2957, 2925, 2854, 2149, 1598, 1453, 1434,

1-Iodo-3-eth yl-4-[(tr im eth ylsilyl)eth yn yl]ben zen e (14).²

4 (3.05 g, 10.0 mmol) and iodomethane (5 mL) afforded 3.25 g

(99%) of the title compound as a dark brown liquid. R_f) 0.55

(hexane). IR (neat) 2964, 2156, 1579, 1472, 1393, 1250, 1183,

1125, 1081, 841, 760, 699, 657 cm^-1

.

¹H NMR (300 MHz,

CDCl₃) δ 7.53 (d, J ) 1.5 Hz, 1 H), 7.44 (dd, J ) 8.1, 1.8 Hz,

1 H), 7.11 (d, J ) 8.1 Hz, 1 H), 2.71 (q, J ) 7.6 Hz, 2 H), 1.20

(t, J ) 7.5 Hz, 3 H), 0.23 (s, 9 H). HRMS calcd for C₁₃H₁₇ISi:

328.0144. Found: 328.0135. λ_max(CH₂Cl₂) ) 266 nm. UV

10% edge value ) 300 nm.

1-(Dieth yltr ia zen yl)-3-eth yl-4-eth yn ylben zen e (17).²

4

(2.98 g, 9.9 mmol), methanol (50 mL), and potassium carbonate

(4.1 g, 30 mmol) afforded 2.22 g (98%) of the title compound

as a clear yellow oil. IR (neat) 3294, 2970, 2099, 1600, 1402,

1236, 1105, 891, 829 cm^-^{1 1}H NMR (300 MHz, CDCl₃) δ 7.41

.

(d, J ) 8.2 Hz, 1 H), 7.25 (d, J ) 1.9 Hz, 1 H), 7.18 (dd, J )

8.2, 2.1 Hz, 1 H), 3.75 (q, J ) 7.2 Hz, 4 H), 3.22 (s, 1 H), 2.80

(q, J ) 7.6 Hz, 2 H), 1.25 (t, J ) 7.5 Hz, 9 H). HRMS calcd for

C₁₄H₁₉N₃: 229.1579. Found: 229.1574.

Eth yl-Con ta in in g Dim er 20.²14 (2.95 g, 9 mmol), 17

(2.24 g, 9.78 mmol), THF (20 mL), bis(dibenzylideneacetone)-

palladium(0) (0.26 g, 0.45 mmol), triphenylphosphine (0.59 g,

2.25 mmol), copper(I) iodide (0.01 g, 0.90 mmol), and N,N-

diisopropylethylamine (6.23 mL, 36 mmol) for 1 d afforded 3.48

g (90%) of the title compound as a yellow oil after gravity liquid

chromatography (24:1; hexane:ether). R_f) 0.56 (24:1; hexane:

1402, 1341, 1238, 1203, 1104, 867, 843, 759, 654 cm^-1

.

¹H

NMR (400 MHz, CDCl₃) δ 7.36 (d, J ) 8.2 Hz, 1 H), 7.21 (d, J

) 1.9 Hz, 1 H), 7.16 (dd, J ) 8.3, 2.0 Hz, 1 H), 3.74 (q, J ) 7.2

Hz, 4 H), 2.74 (t, J ) 7.8 Hz, 2 H), 1.68 (p, J ) 7.7 Hz, 2 H),

1.40-1.24 (m, 24 H), 0.86 (t, J ) 7.0 Hz, 3 H), 0.24 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃) δ 151.12, 146.48, 133.01, 120.92,

118.76, 117.33, 104.79, 96.96, 34.99, 31.92, 30.75, 29.74, 29.69,

29.65, 29.57, 29.36, 22.69, 14.12, 0.10. HRMS calcd for

C₂₇H₄₇N₃Si: 441.3539. Found: 441.3549.

Gen er a l P r oced u r e for Iod id e F or m a t ion fr om Tr i-

a zen es.⁵To a thick-walled oven-dried screw cap tube was

added the corresponding triazene and iodomethane (8 equiv)

as the solvent. The tube was flushed with nitrogen or argon,

sealed, and heated to 120 °C overnight. The reaction was

cooled to room temperature and diluted with hexane. The

smaller oligomers were then filtered through a plug of silica

gel with hexane, and the larger oligomers were filtered through

a plug of silica gel with ethyl acetate.

ether). IR (neat) 2971, 2200, 2153, 1595, 840 cm^-^{1 1}H NMR

.

(300 MHz, CDCl₃) δ 7.43 (d, J ) 8.2 Hz, 1 H), 7.37 (d, J ) 7.9

Hz, 1 H), 7.33 (d, J ) 1.2 Hz, 1 H), 7.29 (d, J ) 1.7 Hz, 1 H),

7.25 (dd, J ) 7.9, 1.6 Hz, 1 H), 7.22 (dd, J ) 8.3, 2.0 Hz, 1 H),

3.76 (q, J ) 7.2 Hz, 4 H), 2.87 (q, J ) 7.6 Hz, 2 H), 2.78 (q, J

) 7.6 Hz, 2 H), 1.30 (t, J ) 7.5 Hz, 6 H), 1.25 (t, J ) 7.4 Hz,

6 H), 0.25 (s, 9 H). ¹³C NMR (75 MHz, CDCl₃) δ 151.4, 147.1,

146.7, 133.0, 132.4, 130.8, 128.6, 124.2, 121.8, 120.4, 118.5,

117.7, 103.7, 99.5, 92.7, 90.5, 28.0, 27.7, 14.9, 14.5, 0.04.

HRMS calcd for C₂₇H₃₅N₃Si: 429.2600. Found: 429.2592.

Eth yl-Con ta in in g Iod id e Dim er 23.²20 (1.93 g, 4.50

mmol) and iodomethane (2.26 mL) afforded 1.98 g (96%) of

the title compound as a brown oil. IR (neat) 2964, 2152, 1579,

1490, 1393, 1250, 1183, 1125, 1081, 841, 760, 699, 657 cm^-1

.

¹H NMR (500 MHz, CDCl₃) δ 7.58 (d, J ) 1.6 Hz, 1 H), 7.49

(dd, J ) 8.1, 1.8 Hz, 1 H), 7.39 (d, J ) 7.9 Hz, 1 H), 7.34 (d, J

) 1.1 Hz, 1 H), 7.27 (dd, J ) 7.9, 1.6 Hz, 1 H), 7.18 (d, J ) 8.1

Hz, 1 H), 2.81 (q, J ) 7.5 Hz, 2 H), 2.80 (q, J ) 7.5 Hz, 2 H),

1.28 (t, J ) 7.6 Hz, 3 H), 1.26 (t, J ) 7.5 Hz, 3 H), 0.26 (s, 9

H). ¹³C NMR (125 MHz, CDCl₃) δ 148.5, 147.2, 137.5, 135.3,

133.9, 132.8, 131.2, 129.0, 123.7, 122.9, 122.3, 103.8, 100.3,

95.1, 94.6, 89.1, 28.0, 27.9, 15.7, 15.0, 14.8, 0.4. HRMS calcd

for C₂₃H₂₅ISi: 456.0770. Found: 456.0769. λ_max(CH₂Cl₂) )

316 nm. UV 10% edge value ) 350 nm.

Gen er a l P r oced u r es for th e Desilyla tion of Alk yn es.

(a) The silylated alkyne was dissolved in methanol, or in some

cases, methanol and dichloromethane to aid in the solubility

of the substrate. Potassium carbonate (2 equiv) was added,

and the reaction was stirred overnight. The reaction mixture

was then subjected to an aqueous workup and the aqueous

layer extracted with ether, dichloromethane or ethyl acetate

(3×). After drying the combined organic layers over magne-

sium sulfate, the solvent was removed in vacuo. The crude

product was then filtered through a plug of silica gel, yielding

the free alkyne which was used without further purification.

Eluents and other slight modifications are described below for

each material. (b) The silylated alkynes was dissolved in THF

and cooled to 0 °C. TBAF (1.5 equiv, 1.0 M in THF) was added,

and the reaction was stirred overnight. The reaction mixture

was then subjected to an aqueous workup and the aqueous

layer extracted with ether, dichloromethane, or ethyl acetate

(3×). After drying the combined organic layers over magne-

sium sulfate, the solvent was removed in vacuo. The crude

product was then filtered through a plug of silica gel, yielding

the free alkyne which was used without further purification.

Eluents and other slight modifications are described below for

each material. (c) The silylated alkynes was dissolved in

pyridine (0.5 M) in a plastic vessel. A preformed solution of

concentrated hydrofluoric acid (1.1 equiv) in TBAF (2.2 equiv,

1.0 M in THF) was added at room temperature and allowed

to stir for 15 to 30 min before being quenched with silica gel.

The reaction mixture was then filtered and subjected to an

aqueous workup, and the aqueous layer was extracted with

Eth yl-Con ta in in g Ter m in a l Alk yn yl Dim er 26.²20

(1.07 g, 2.50 mmol), methanol (10 mL) and potassium carbon-

ate (1.04 g, 7.50 mmol) afforded 0.89 g (100%) of the title

compound as a brown oil. ¹H NMR (500 MHz, CDCl₃) δ 7.43

(dd, J ) 8.0, 0.3 Hz, 1 H), 7.41 (d, J ) 7.9 Hz, 1 H), 7.35 (d, J

) 1.3 Hz, 1 H), 7.28 (d, J ) 1.8 Hz, 1 H), 7.27 (ddd, J ) 8.1,

1.8, 0.3 Hz, 1 H), 7.22 (dd, J ) 8.2, 1.9 Hz, 1 H), 3.76 (q, J )

7.2 Hz, 4 H), 3.31 (s, 1 H), 2.86 (q, J ) 7.5 Hz, 3 H), 2.80 (q,

J ) 7.6 Hz, 3 H), 1.30 (t, J ) 7.6 Hz, 3 H), 1.25 (t, J ) 7.5 Hz,

6 H), 1.19 (t, J ) 7.0 Hz, 3 H). ¹³C NMR (125 MHz, CDCl₃) δ

151.9, 147.5, 147.3, 133.4, 133.2, 131.2, 129.0, 124.9, 121.2,

120.8, 118.9, 118.1, 92.9, 91.0, 82.6, 82.5, 28.4, 27.9, 15.3, 15.1.

HRMS calcd for C₂₄H₂₇N₃: 357.2205. Found: 357.2202.

Eth yl-Con ta in in g Tetr a m er 29. 23 (0.91 g, 2.0 mmol),

26 (0.73 g, 2.06 mmol), THF (4 mL), bis(dibenzylideneacetone)-

palladium(0) (57.40 mg, 0.10 mmol), triphenylphosphine (105

mg, 0.40 mmol), copper(I) iodide (38.1 mg, 0.20 mmol), and

N,N-diisopropylethylamine (1.38 mL, 8 mmol) for 5 d afforded

1.17 g (93%) of the title compound as a yellow solid after

1402 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

gravity liquid chromatography (24:1; hexane:ether). R_f) 0.26

g (78 %) of the title compound as a yellow oil. IR (neat) 2957,

(24:1; hexane:ether). IR (KBr) 2965, 2872, 2151, 1590, 1503,

2151, 1464, 1402, 1236, 1103, 843 cm^-1

.

¹H NMR (300 MHz,

1401, 1246, 841 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.46 (d,

CDCl₃) δ 7.45-7.27 (m, 6 H), 3.76 (q, J ) 7.2 Hz, 4 H), 2.83-

2.62 (m, 4 H), 1.80-1.60 (m, 2 H), 1.40-1.11 (m, 26 H), 0.99-

0.80 (m, 12 H), 0.25 (s, 9 H). LRMS calcd for C₄₁H₆₃N₃Si: 625.

Found: 625. λ_max(CH₂Cl₂) ) 362 nm. UV 10% edge value )

410 nm. M_n) 715, M_w) 744, M_w/M_n) 1.04.

J ) 7.9 Hz, 1 H), 7.45 (d, J ) 8.0 Hz, 1 H), 7.45 (d, J ) 8.2 Hz,

1 H), 7.40 (d, J ) 7.8 Hz, 1 H), 7.39 (br m, 2 H), 7.35 (d, J )

1.3 Hz, 1 H), 7.32 (dd, J ) 7.9, 1.7 Hz, 1 H), 7.32 (dd, J ) 7.9,

1.7 Hz, 1 H), 7.29 (d, J ) 1.9, 1 H), 7.27 (dd, J ) 8.2, 1.6 Hz,

1 H), 7.23 (dd, J ) 8.2, 2.1 Hz, 1 H), 3.76 (q, J ) 7.2 Hz, 4 H),

2.885 (q, J ) 7.5 Hz, 2 H), 2.884 (q, J ) 8.2 Hz, 2 H), 2.87 (q,

J ) 7.5 Hz, 2 H), 2.79 (q, J ) 7.6 Hz, 2 H), 1.32 (t, J ) 7.6 Hz,

6 H), 1.31 (t, J ) 7.6 Hz, 3 H), 1.26 (t, J ) 7.6 Hz, 3 H), 0.25

(s, 9 H). ¹³C NMR (75 MHz, CDCl₃) δ 151.75, 147.50, 147.22,

146.69, 146.62, 133.29, 132.75, 132.54, 132.50, 131.33, 131.26,

131.21, 129.18, 129.06, 129.03, 124.45, 123.85, 123.79, 122.78,

122.68, 122.16, 120.72, 118.88, 117.96, 103.82, 100.29, 94.99,

94.80, 93.08, 90.93, 89.98, 89.73, 28.33, 28.05, 28.03, 27.99,

15.21, 15.05, 15.01, 14.80, 0.33. HRMS calcd for C₄₇H₅₁N₃Si:

685.3852. Found: 685.3843.

3-Eth ylh ep tyl-Con ta in in g Iod id e Dim er 24. 21 (0.22 g,

0.35 mmol) and iodomethane (2 mL) afforded 0.23 g (100%) of

the title compound as a yellow liquid. IR (neat) 2956, 2152,

1464, 1249, 843, 760 cm^-^{1 1}H NMR (300 MHz, CDCl₃) δ 7.57

.

(s, 1 H), 7.48 (d, J ) 8.1 Hz, 1 H), 7.38 (d, J ) 8.0 Hz, 1 H),

7.31 (s, 1 H), 7.23 (d, J ) 7.7 Hz, 1 H), 7.17 (d, J ) 8.1 Hz, 1

H), 2.74 (m, 4 H), 1.64-1.58 (m, 2 H), 1.43-1.20 (m, 20 H),

0.96-0.82 (m, 12 H), 0.25 (s, 9 H).

3-Eth ylh ep tyl-Con ta in in g Ter m in a l Alk yn yl Dim er 27.

21 (0.23 g, 0.37 mmol), THF (2 mL), and TBAF (0.5 mL, 0.5

mmol, 1.0 M in THF) afforded 0.2 g (98%) of the title compound

as a yellow oil. IR (neat) 3300, 2956, 2200, 2102, 1597, 1464,

Eth yl-Con ta in in g Iod id e Tetr a m er 32. 29 (136.70 mg,

0.20 mmol) and iodomethane (4 mL) afforded 142.40 mg (98%)

of the title compound as a light yellow solid. IR (KBr) 2965,

1237, 1104 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.44-7.40 (m,

.

2 H), 7.33 (s, 1 H), 7.26-7.21 (m, 3 H), 3.75 (q, J ) 7.1 Hz, 4

H), 3.30 (s, 1 H), 2.85-2.63 (m, 4 H), 1.63-1.57 (m, 2 H), 1.44-

1.22 (m, 26 H), 0.98-0.81 (m, 12 H).

2930, 2151, 1500, 1459, 1249, 888, 841 cm^-1

.

¹H NMR (500

MHz, CDCl₃) δ 7.60 (d, J ) 1.6 Hz, 1 H), 7.51 (dd, J ) 8.1, 1.7

Hz, 1 H), 7.47 (d, J ) 7.7 Hz, 2 H), 7.41-7.38 (4 line m, 3 H),

7.37-7.28 (m, 4 H), 7.20 (d, J ) 8.1 Hz, 1 H), 2.89 (q, J ) 7.5

Hz, 2 H), 2.88 (q, J ) 7.5 Hz, 2 H), 2.83 (q, J ) 7.6 Hz, 2 H),

2.81 (q, J ) 7.6 Hz, 2 H), 1.33 (t, J ) 7.6 Hz, 3 H), 1.29 (t, J

) 7.6 Hz, 6 H), 1.27 (t, J ) 7.6 Hz, 3 H), 0.27 (s, 9 H). ¹³C

NMR (75 MHz, CDCl₃) δ 148.57, 147.23, 146.73, 146.72,

137.47, 135.26, 133.88, 132.77, 132.72, 132.57, 131.35, 131.33,

131.27, 129.22, 129.19, 129.05, 128.38, 126.07, 123.77, 123.72,

123.63, 122.87, 122.83, 122.31, 103.83, 100.34, 95.16, 95.11,

94.66, 89.76, 89.70, 89.16, 28.06, 28.01, 27.93, 15.03, 14.96,

14.82, 0.35. HRMS calcd for C₄₃H₄₁ISi: 712.2022. Found:

712.2028. λ_max(CH₂Cl₂) ) 352 nm. UV 10% edge value ) 385

nm.

3-Eth ylh ep tyl-Con ta in in g Tetr a m er 30. Bis(dibenzyli-

deneacetone)palladium(0) (13.8 mg, 0.024 mmol), triphen-

ylphosphine (31.5 mg, 0.12 mmol), copper(I) iodide (9.1 mg,

0.048 mmol), 24 (0.29 g, 0.48 mmol), 27 (0.27 mg, 0.48 mmol),

THF (5 mL), diisopropylamine (0.5 mL), and purification by

flash chromatography on silica gel (3:1; hexane:dichloromethane)

afforded 0.23 g (44%) of the title compound as a yellow oil. IR

(neat) 2956, 2151, 1595, 1464, 1402, 1236, 1103 cm^-^{1 1}H NMR

.

(300 MHz, CDCl₃) δ 7.48-7.27 (m, 12 H), 3.76 (q, J ) 7.1 Hz,

4 H), 2.98-2.70 (m, 8 H), 1.82-1.63 (m, 4 H), 1.59-1.05 (m,

46 H), 1.05-0.78 (m, 24 H), 0.27 (s, 9 H). LRMS calcd for

C₇₅H₁₀₇N₃Si: 1077.8. Found: 1077.9. λ_max(CH₂Cl₂) ) 372 nm.

UV 10% edge value ) 421 nm. M_n) 1335, M_w) 1388, M_w/

M_n) 1.06.

Eth yl-Con ta in in g Ter m in a l Alk yn yl Tetr a m er 35. 29

(0.29 g, 0.42 mmol), THF (5 mL), and TBAF (0.6 mL, 0.6 mmol,

1.0 M in THF) afforded 0.14 g (55%) of the title compound as

3-Eth ylh ep tyl-Con ta in in g Iod id e Tetr a m er 33. 30 (0.13

g, 0.12 mmol) and iodomethane (3 mL) afforded 0.12 g (100%)

of the title compound as a yellow oil. IR (neat) 2955, 2151,

1

a light yellow solid. A H NMR was run to examine the loss

of the trimethylsilyl peak, and the material was used directly

in the next reaction.

1464, 1378, 1249, 859 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.59

.

(s, 1 H), 7.50-7.24 (m, 10 H), 7.19 (d, J ) 8.5 Hz, 1 H), 2.96-

2.65 (br m, 8 H), 1.80-1.59 (m, 4 H), 1.59-1.10 (m, 40 H),

1.10-0.89 (m, 24 H), 0.28 (s, 9 H). LRMS calcd for C₇₃H₉₇ISi:

1104.6. Found: 1104.7.

Eth yl-Con tain in g Octam er 38. Bis(dibenzylideneacetone)-

palladium(0) (3.4 mg, 0.006 mmol), triphenylphosphine (7.9

mg, 0.03 mmol), copper(I) iodide (2.3 mg, 0.012 mmol), 32 (41.9

mg g, 0.06 mmol), 35 (42.9 mg, 0.07 mmol), THF (2 mL), and

diisopropylamine (0.5 mL, 3.5 mmol) at 60 °C overnight

afforded a solid that was filtered and rinsed with water and

dichloromethane. Due to its insolubility, the solid was only

characterized by direct exposure mass spectrometry and UV

spectroscopy. Direct exposure MS statistical isotopic range

calcd for C₈₇H₈₃N₃Si: 1198 (95%), 1199 (100%), 1200 (55%).

Found: 1098.6 (signifying loss of the triazene moiety at 100

amu). λ_max(CH₂Cl₂) ) 364 nm. UV 10% edge value ) 500

nm.

3-Eth ylh ep tyl-Con ta in in g Ter m in a l Alk yn yl Tetr a m er

36. 30 (0.11 g, 0.1 mmol), THF (2 mL), and TBAF (0.15 mL,

0.15 mmol, 1.0 M in THF) afforded 0.1 g (100%) of the title

compound as a yellow oil. IR (neat) 2928, 2360, 2344, 1464,

1401, 1236, 1103, 827 cm^-1

.

¹H NMR (500 MHz, CDCl₃) δ

7.42-7.21 (m, 12 H), 3.76 (q, J ) 7.2 Hz, 4 H), 3.36 (s, 1 H),

2.95-2.76 (m, 8 H), 1.80-1.60 (m, 4 H), 1.60-1.10 (m, 46 H),

1.10-0.75 (m, 24 H).

Octom er 39. Bis(dibenzylideneacetone)palladium(0) (6.9

mg, 0.012 mmol), triphenylphosphine (15.7 mg, 0.06 mmol),

copper(I) iodide (2.3 mg, 0.012 mmol), 33 (0.13 g, 0.12 mmol)

36 (0.1 mg, 0.1 mmol), THF (2 mL), and diisopropylamine (0.5

mL) at 60 °C for 12 h, and flash chromatography on silica gel

(3:1; hexane:dichloromethane) afforded 0.17 g (70%) of the title

compound as a yellow solid. IR (neat) 2952, 2198, 2147, 1464,

3-Eth ylh ep tyl-Con ta in in g Iod id e Mon om er 15. 9 (0.79

g, 2.0 mmol) and iodomethane (2 mL) afforded 0.78 g (92%) of

the title compound as a yellow liquid. IR (neat) 2957, 2156,

1579, 1472, 1249, 1184, 844, 760 cm^-1

.

¹H NMR (300 MHz,

CDCl₃) δ 7.52 (s, 1 H), 7.43 (d, J ) 8.1 Hz, 1 H), 7.11 (d, J )

8.1 Hz, 1 H), 2.72-2.62 (m, 2 H), 1.60 (br s, 1 H), 1.32-1.21

(m, 8 H), 0.95-0.84 (m, 6 H), 0.23 (s, 9 H).

827 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.48-7.27 (m, 24 H),

3.77 (q, J ) 7.1 Hz, 4 H), 2.98-2.63 (m, 16 H), 1.84-1.58 (m,

8 H), 1.58-1.10 (m, 86 H), 1.10-0.78 (m, 48 H), 0.27 (9 H).

3-Eth ylh ep tyl-Con ta in in g Ter m in a l Alk yn yl Mon om er

18. 9 (0.93 g, 2.3 mmol), THF (6 mL), and TBAF (2.6 mL, 2.6

mmol, 1.0 M in THF) afforded 0.72 g (96%) of the title

compound as a yellow liquid. IR (neat) 3311, 2931, 2099, 1599,

λ_max(CH₂Cl₂) ) 376. UV 10% edge value ) 422 nm. M_n

)

2800, M_w) 2960, M_w/M_n) 1.05. MALDI MS (sinapinic acid

matrix, positive ion mode) average molecular weight calculated

for C₁₄₃H₁₉₅N₃Si: 1984. Found peak maximum (M + 1): 1791

( 9 (large error due to broad signal), (loss of SiMe₃at 73 amu,

N₃Et₂at 100 amu, CtC at 24 amu which is a common phenyl-

alkynyl cleavage route).¹⁸

1402, 1239, 891 cm^-^{1 1}H NMR (300 MHz, CDCl₃) δ 7.39 (d,

.

J ) 8.2 Hz, 1 H), 7.22 (s, 1 H), 7.18 (d, J ) 8.2 Hz, 1 H), 3.74

(q, J ) 7.2 Hz, 4 H), 3.21 (s, 1 H), 2.79-2.74 (4 line m, 2 H),

1.64-1.55 (m, 1 H), 1.50-1.19 (m, 16 H), 0.99-0.83 (m, 6 H).

3-E t h ylh ep t yl-Con t a in in g Dim er 21. Bis(dibenzyli-

deneacetone)palladium(0) (57.4 mg, 0.1 mmol), triphenylphos-

phine (130 mg, 0.5 mmol), copper(I) iodide (38.1 mg, 0.2 mmol),

15 (0.78 g, 1.8 mmol), 18 (0.61 g, 1.8 mmol), THF (5 mL),

diisopropylamine (1.0 mL) and purification by flash chroma-

tography on silica gel (19:1; hexane:ethyl acetate) afforded 0.88

3-Eth ylh ep tyl-Con ta in in g Iod id e Octa m er 41. 39 (83.7

mg, 0.04 mmol) and iodomethane (3 mL) afforded 80 mg

(100%) of the title compound as a yellow solid. IR (neat) 2955,

2926, 2858, 2160, 1592, 1502, 1461, 826 cm^-^{1 1}H NMR (500

.

MHz, CDCl₃) δ 7.58-7.18 (m, 24 H), 2.98-2.62 (m, 16 H),

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1403

1.82-1.55 (m, 8 H), 1.55-1.10 (m, 80), 1.10-0.70 (m, 48 H),

0.26 (s, 9 H).

palladium(0) (0.024 g, 0.041 mmol), triphenylphosphine (0.055

g, 0.21 mmol), copper(I) iodide (0.016 g, 0.082 mmol), and N,N-

diisopropylethylamine (0.57 mL, 3.28 mmol) for 3 d afforded

0.50 g (85%) of the title compound as a yellow oil after gravity

liquid chromatography (24:1; hexane:ether). R_f) 0.44 (24:1;

hexane:ether). IR (neat) 2922, 2853, 2202, 2151, 1596, 1495,

3-Eth ylh ep tyl-Con ta in in g Ter m in a l Alk yn yl Octa m er

43. 39 (28.6 g, 0.01 mmol), THF (2 mL), and TBAF (0.1 mL,

0.1 mmol, 1.0 M in THF) afforded 19.1 mg (100%) of the title

compound as a yellow solid. IR (neat) 2927, 2361, 2343, 1458

1465, 1404, 1378, 1332, 1249, 1210, 1103, 862, 760, 633 cm^-1

.

cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.47-7.23 (m, 24 H), 3.74

.

¹H NMR (400 MHz, CDCl₃) δ 7.42 (d, J ) 8.2 Hz, 1 H), 7.37

(d, J ) 7.9 Hz, 1 H), 7.30 (s, 1 H), 7.26-7.25 (m, 1 H), 7.22 (d,

J ) 8.2 Hz, 1 H), 7.21 (d, J ) 8.3 Hz, 1 H), 3.76 (q, J ) 7.2 Hz,

4 H), 2.82 (t, J ) 7.7 Hz, 2 H), 2.73 (t, J ) 7.7 Hz, 2 H), 1.69

(p, J ) 7.2 Hz, 2 H), 1.63 (p, J ) 7.2 Hz, 2 H), 1.32-1.22 (m,

42 H), 0.86 (t, J ) 7.0 Hz, 6 H), 0.24 (s, 9 H). ¹³C NMR (100

MHz, CDCl₃) δ 151.19, 145.97, 145.59, 132.84, 132.30, 131.49,

128.42, 124.03, 121.99, 121.15, 118.78, 117.59, 103.85, 99.24,

92.58, 90.71, 35.03, 34.73, 31.99, 31.65, 30.91, 30.64, 29.78,

29.76, 29.73, 29.64, 29.61, 29.43, 22.75, 22.71, 14.17, 0.01

HRMS calcd for C₄₇H₇₅N₃Si: 709.5730. Found: 709.5697.

Dod ecyl-Con ta in in g Iod id e Dim er 25 fr om 22. 22 (0.25

g, 0.35 mmol) and iodomethane (3 mL) afforded 0.24 g (95%)

of the title compound as a yellow oil. R_f) 0.63 (hexane). IR

(neat) 2923, 2854, 2152, 1945, 1892, 1775, 1600, 1579, 1541,

1490, 1465, 1406, 1393, 1378, 1351, 1302, 1249, 1225, 1194,

(q, J ) 7.9 Hz, 4 H), 3.22 (s, 1 H), 2.98-2.65 (m, 16 H), 1.80-

1.60 (m, 8 H), 1.60-1.05 (m, 86 H), 1.05-0.70 (m, 48 H).

3-E t h ylh ep t yl-Con t a in in g 16-m er 45. Bis(dibenzyli-

deneacetone)palladium(0) (1.6 mg, 0.0028 mmol), triphen-

ylphosphine (3.7 mg, 0.014 mmol), copper(I) iodide (0.5 mg,

0.0028 mmol), 41 (37.0 g, 0.018 mmol), 43 (0.26.3 mg, 0.014

mmol), THF (2 mL), and diisopropylamine (0.25 mL) at 60 °C

for 12 h, and flash chromatography on silica gel (3:1; hexane:

dichloromethane), afforded 30.8 mg of a 1:1 mixture of the title

compound and unreacted iodide 41 (approximately 15.4 mg

(26%) of the title compound). The two compounds could not

be separated by flash chromatography, but they could be

detected by SEC using UV detection (λ_max) 376). One of the

two peaks indeed corresponded to the iodooctamer 41, and the

second peak had an M_nvalue more than double that of the

41. An analytically pure sample of the 16-mer 45 was obtained

by adding diethyl ether and centrifuging the mixture. The

liquid was decanted away from the remaining solid, and the

procedure was repeated. After four such washing cycles, the

remaining solid was examined by SEC to reveal a single

product which was used for the analytical analysis. IR (neat)

1144, 1117, 1092, 1015, 947, 843, 760, 722, 700, 687, 633 cm^-1

.

¹H NMR (400 MHz, CDCl₃) δ 7.56 (d, J ) 1.5 Hz, 1 H), 7.48

(dd, J ) 8.1, 1.7 Hz, 1 H), 7.37 (d, J ) 7.9 Hz, 1 H), 7.30 (d, J

) 1.0 Hz, 1 H), 7.23 (dd, J ) 8.0, 1.4 Hz, 1 H), 7.17 (d, J ) 8.1

Hz, 1 H), 2.76-2.71 (m, 4 H), 1.64-1.62 (m, 4 H), 1.32-1.22

(m, 36 H), 0.86 (t, J ) 7.0 Hz, 6 H), 0.24 (s, 9 H). ¹³C NMR

(100 MHz, CDCl₃) δ 147.10, 145.70, 137.76, 134.80, 133.43,

132.34, 131.58, 128.52, 123.14, 122.64, 122.01, 103.57, 99.70,

94.55, 94.08, 88.88, 34.68, 34.50, 31.95, 30.60, 30.64,

29.70, 29.68, 29.65, 29.56, 29.50, 29.39, 22.71, 14.15, 14.14,

-0.031. Anal. Calcd for C₄₃H₆₅ISi: C, 70.08; H, 8.89; I,

17.22. Found: C, 69.84; H, 8.77; I, 17.42. HRMS calcd for

C₄₃H₆₅ISi: 736.3900. Found: 736.3904. M_n) 900, M_w) 929,

M_w/ M_n) 1.03. λ (THF) ) 314 (ꢀ 5.94 × 10⁴M^-1cm^-1), 335

nm. Emiss (THF) ) 334, 351, 386 nm.

2956, 2927, 2360, 2340, 1506, 1458 cm^-^{1 1}H NMR (300 MHz,

.

CDCl₃) δ 7.47-7.24 (m, 48 H), 3.77 (q, J ) 7.1 Hz, 4 H), 2.95-

2.65 (m, 32 H), 1.82-1.58 (m, 16 H), 1.58-1.10 (m, 166 H),

1.10-0.70 (m, 96 H), 0.26 (s, 9 H). λ_max(CH₂Cl₂) ) 376 nm.

UV 10% edge value ) 422 nm. M_n) 6649, M_w) 7114, M_w/

M_n) 1.07. MALDI-MS (sinapinic acid matrix, positive ion

mode) average molecular weight calculated for 23 with

C₂₇₉H₃₇₁N₃Si: 3795. Found (M + 1): 3486 ( 14 (large error

due to broad signal) (signifying loss in the MS of the SiMe₃at

73 amu, N₃Et₂at 100 amu, CtC at 24 amu which a common

phenyl-alkynyl cleavage route, and a C₈H₁₇fragment at 113

amu which represents a typical benzylic methylene-ethylene

cleavage site.)¹⁸

Dod ecyl-Con ta in in g Ter m in a l Alk yn yl Dim er 28. 22

(2.84 g, 4 mmol), methanol (4 mL), dichloromethane (4 mL),

and potassium carbonate (1.66 g, 12 mmol) afforded 2.55 g

(100%) of the title compound as a dark yellow oil. IR (neat)

3302, 2925, 2853, 2201, 2102, 1596, 1496, 1465, 1401, 1332,

1-Iodo-3-dodecyl-4-[(tr im eth ylsilyl)eth yn yl]ben zen e (16)

P r ep a r ed fr om 13. 13 (4.70 g, 10.64 mmol) and iodomethane

(5.30 mL) afforded 4.70 g (94%) of the title compound as a light

brown oil. R_f) 0.88 (hexane). IR (neat) 2956, 2924, 2854,

2156, 1579, 1543, 1472, 1392, 1250, 1183, 1128, 844, 816, 760,

1237, 1210, 1103, 891, 828, 721, 644 cm^-^{1 1}H NMR (300 MHz,

.

CDCl₃) δ 7.48 (d, J ) 8.2 Hz, 1 H), 7.45 (d, J ) 8.0 Hz, 1 H),

7.38 (d, J ) 1.2 Hz, 1 H), 7.33 (dd, J ) 4.3, 1.8 Hz, 1 H), 7.29

(d, J ) 8.2 Hz, 1 H), 7.28 (d, J ) 7.9 Hz, 1 H), 3.77 (q, J ) 7.2

Hz, 4 H), 3.33 (s, 1 H), 2.89 (t, J ) 7.5 Hz, 2 H), 2.81 (t, J )

7.5 Hz, 2 H), 1.77 (p, J ) 7.3 Hz, 2 H) 1.69 (p, J ) 7.3 Hz, 2

H), 1.43-1.20 (m, 42 H), 0.91 (t, J ) 6.9 Hz, 6 H). ¹³C NMR

(100 MHz, CDCl₃) δ 151.24, 145.98, 145.61, 132.86, 132.81,

131.48, 128.47, 127.54, 124.39, 121.18, 121.03, 118.73, 117.62,

92.43, 90.78, 82.31, 81.86, 35.06, 34.39, 32.01, 30.93, 30.54,

29.81, 29.78, 29.75, 29.69, 29.67, 29.56, 29.54, 29.47, 29.46,

22.77, 14.19. HRMS calcd for C₄₄H₆₇N₃: 637.5335. Found:

637.5325.

658 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.51 (d, J ) 1.7 Hz,

.

1 H), 7.43 (dd, J ) 8.1, 1.8 Hz, 1 H), 7.11 (d, J ) 8.1 Hz, 1 H),

2.66 (t, J ) 7.7 Hz, 2 H), 1.58 (p, J ) 7.2 Hz, 2 H), 1.30-124

(m, 18 H), 0.86 (t, J ) 7.1 Hz, 3 H), 0.23 (s, 9 H). ¹³C NMR

(100 MHz, CDCl₃) δ 147.59, 137.65, 134.61, 133.63, 122.10,

103.04, 99.24, 94.69, 34.53, 31.95, 30.53, 29.70, 29.68 (2 C),

29.65, 29.61, 29.49, 29.39, 22.72, 14.16, -0.050. Anal. Calcd

for C₂₃H₃₇ISi: C, 58.96; H, 7.96; I, 27.09. Found: C, 58.70;

H, 7.91; I, 27.27. HRMS calcd for C₂₃H₃₇ISi: 468.1709.

Found: 468.1700. λ (THF) ) 263 (ꢀ 2.50 × 10⁴M^-1cm^-1),

273, 275, 296 nm.

Dod ecyl-Con ta in in g Tetr a m er 31. 25 (2.69 g, 3.65

mmol), 28 (2.55 g, 4.01 mmol), THF (8 mL), bis(dibenzyli-

deneacetone)palladium(0) (0.10 g, 0.18 mmol), triphenylphos-

phine (0.24 g, 0.91 mmol), copper(I) iodide (0.070 g, 0.37 mmol),

and N,N-diisopropylethylamine (2.54 mL, 14.60 mmol) for 2

d afforded 3.97 g (87%) of the title compound as a yellow oil

which solidified upon standing after gravity liquid chroma-

tography (24:1; hexane:ether). R_f) 0.54 (24:1; hexane:ether).

IR (neat) 2921, 2851, 2898, 2151, 1592, 1502, 1467, 1406, 1378,

1352, 1247, 1235, 1212, 1095, 884, 862, 843, 828, 759, 721,

1-(Dieth yltr ia zyl)-3-d od ecyl-4-eth yn ylben zen e (19). 13

(4.70 g, 10.64 mmol), methanol (10 mL), dichloromethane (10

mL), and potassium carbonate (4.41 g, 31.92 mmol) afforded

3.79 g (97%) of the title compound as a yellow oil. R_f) 0.20

(hexane). IR (neat) 3310, 2926, 2855, 2099, 1677, 1600, 1458,

1400, 1340, 1237, 1101, 829 cm^-^{1 1}H NMR (500 MHz, CDCl₃)

.

δ 7.45 (d, J ) 8.2 Hz, 1 H), 7.30 (d, J ) 2.0 Hz, 1 H), 7.25 (dd,

J ) 8.2, 2.0 Hz, 1 H), 3.76 (q, J ) 7.1 Hz, 4 H), 3.24 (s, 1 H),

2.33 (t, J ) 7.7 Hz, 2 H), 1.71 (p, J ) 7.3 Hz, 2 H), 1.43-1.24

(m, 24 H), 0.92 (t, J ) 7.1 Hz, 3 H). ¹³C NMR (125 MHz,

CDCl₃) δ 151.81, 146.76, 133.89, 121.46, 118.25, 117.86, 83.54,

80.40, 35.11, 32.40, 31.12, 30.18 (2 C), 30.13, 30.09, 30.01,

29.98, 29.84, 23.16, 14.57. HRMS calcd for C₂₄H₃₉N₃: 369.3144.

Found: 369.3144.

634 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.50 (d, J ) 8.2 Hz,

.

1 H), 7.49 (d, J ) 7.9 Hz, 2 H), 7.44 (d, J ) 8.0 Hz, 1 H), 7.42

(s, 1 H), 7.38-7.34 (m, 4 H), 7.32 -7.29 (m, 2 H), 3.78 (q, J )

7.1 Hz, 4 H), 2.90 (m, 6 H), 2.82 (t, J ) 7.9 Hz, 2 H), 1.90-

1.70 (m, 8 H), 1.40-1.28 (m, 78 H), 0.94-0.89 (m, 12 H), 0.31

(s, 9 H). ¹³C NMR (100 MHz, CDCl₃) δ 151.21, 145.98, 145.71,

145.19, 145.11, 132.88, 132.38, 132.16, 132.12, 131.73, 131.64,

131.61, 128.76, 128.63, 128.61, 124.02, 123.42, 123.38, 122.62,

122.53, 122.03, 121.20, 118.84, 117.63, 103.69, 99.65, 94.58,

94.40, 92.70, 90.86, 89.90, 89.65, 35.08, 34.76, 32.03, 30.94,

Dod ecyl-Con ta in in g Dim er 22. 16 (0.38 g, 0.82 mmol),

19 (0.42 g, 1.15 mmol), THF (4 mL), bis(dibenzylideneacetone)-

(18) McLafferty, F. W.; Turecek, F. Interpretation of Mass Spectra,

4th ed.; University Science: Mill Valley, California, 1993.

1404 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

30.74, 30.65, 29.83, 29.82, 29.78, 29.69, 29.67, 29.65, 29.63,

29.49, 29.46, 22.78, 22.73, 14.20, 0.01. LRMS calcd for

C₈₇H₁₃₁N₃Si: 1246 (96%), 1247 (100%), 1248 (54%). Found:

1246 (100%), 1247 (91%), 1248 (55%).

(125 MHz, CDCl₃) δ 147.52, 147.47, 146.11, 145.62, 145.55,

145.31, 143.57, 138.18, 138.14, 135.23, 135.18, 133.85, 133.60,

132.77, 132.56, 132.14, 132.03, 131.91, 131.86, 129.16, 129.12,

128.98, 128.80, 124.09, 123.81, 123.70, 123.64, 123.52, 123.50,

123.38, 123.20, 123.09, 123.06, 122.65, 122.54, 104.04, 100.10,

95.20, 95.10, 95.02, 94.97, 94.78, 94.67, 94.58, 91.43, 90.06,

89.96, 89.88, 88.74, 88.53, 87.90, 39.82, 39.50, 39.44, 39.28,

37.53, 37.06, 36.91, 35.50, 35.11, 34.94, 34.81, 34.77, 34.71,

33.21, 32.83, 32.70, 32.51, 32.38, 32.34, 31.77, 31.41, 31.34,

31.08, 31.02, 31.00, 30.82, 30.60, 30.42, 30.17, 30.13, 30.08,

30.01, 29.93, 29.91, 29.83, 29.80, 29.67, 29.41, 28.91, 28.61,

28.40, 28.31, 27,85, 27.74, 27.55, 27.43, 27.14, 23.49, 23.26,

23.13, 23.09, 22.99, 20.57, 20.11, 19.65, 14.82, 14.68, 14.55,

14.40, 11.83, 4.96, 0.38. Anal. Calcd for C₁₆₃H₂₃₃ISi: C, 83.39;

H, 10.00. Found: C, 81.43; H, 9.32. M_n) 3625, M_w) 4350,

Dod ecyl-Con ta in in g Iod id e Tetr a m er 34 fr om 31. 31

(1.99 g, 1.60 mmol) and iodomethane (2 mL) afforded 1.88 g

(92%) of the title compound as a yellow oil which solidified

upon standing. IR (KBr) 2924, 2853, 2203, 2151, 1697, 1657,

1598, 1543, 1500, 1463, 1384, 1252, 1183, 1005, 656, 761, 723,

634 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.57 (d, J )1.7 Hz, 1

.

H), 7.49 (dd, J ) 8.0, 1.7 Hz, 1 H), 7.45 (d, J ) 7.9 Hz, 2 H),

7.44 (d, J ) 7.8 Hz, 1 H), 7.39 (d, J ) 1.0 Hz, 1 H), 7.35 (d, J

) 1.3 Hz, 1 H), 7.31-7.26 (m, 4 H), 7.18 (d, J ) 8.2 Hz, 1 H),

2.85-2.75 (m, 8 H), 1.67 (m, 8 H), 1.40-1.20 (m, 72 H), 0.86-

0.84 (m, 12 H), 0.25 (s, 9 H). ¹³C NMR (100 MHz, CDCl₃) δ

147.11, 145.70, 145.21, 137.78, 134.82, 133.44, 132.87, 132.36,

132.15, 131.70, 131.62, 128.72, 128.57, 123.28, 123.21, 123.11,

122.68, 122.62, 122.12, 103.63, 99.70, 94.68, 94.61, 94.57,

94.17, 89.60, 89.55, 89.00, 34.69, 34.53, 34.36, 31.97, 30.67,

30.62, 30.49, 29.75, 29.71, 29.66, 29.59, 29.53, 29.42, 28.00,

27.15, 22.73, 19.70, 14.15, 11.42, -0.018. Anal. Calcd for

C₈₃H₁₂₁ISi: C, 78.26; H, 9.57. Found: C, 77.30; H, 9.24.

LRMS calcd for C₈₃H₁₂₁ISi: 1273 (99%), 1274 (100%), 1275

M_w/ M_n) 1.20. λ (THF) ) 242, 370 (ꢀ 1.72 × 10⁵M^-1cm^-1

)

nm. Emiss (THF) ) 411, 433 nm.

Dod ecyl-Con ta in in g Ter m in a l Alk yn yl Octa m er 44. 40

(0.18 g, 0.11 mmol), methanol (5 mL), dichloromethane (15

mL), and potassium carbonate (0.15 g, 1.05 mmol) at 65 °C

afforded 0.13 g (100%) of the title compound as a yellow oil

which solidified upon standing. IR (KBr) 3310, 2924, 2854,

2198, 1593, 1502, 1460, 1403, 1343, 1234, 1096, 889, 837, 723,

612 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.50-7.43 (m, 9 H),

.

(53%). Found: 1273 (100%), 1274 (98%), 1275 (50%). M_n

)

1706, M_w) 1777, M_w/ M_n) 1.04. λ (THF) ) 241, 273, 350 (ꢀ

1.10 × 10⁵M^-1cm^-1) nm. Emiss (THF) ) 391, 412 nm.

Dod ecyl-Con ta in in g Ter m in a l Alk yn yl Tetr a m er 37.

31 (0.14 g, 0.11 mmol), methanol (2 mL), dichloromethane (4

mL), and potassium carbonate (0.14 g, 1.0 mmol) afforded 0.13

g (100%) of the title compound as a yellow oil which solidified

upon standing. IR (neat) 3314, 3029, 2921, 2851, 2198, 2100,

1594, 1503, 1465, 1403, 1350, 1234, 1095, 885, 828, 722, 648

7.38-7.26 (m, 15 H), 3.76 (q, J ) 7.0 Hz, 4 H), 3.32 (s, 1 H),

2.83 (m, 16 H), 1.71 (m, 16 H), 1.34 -1.23 (m, 152 H), 0.85-

0.83 (m, 24 H).

Dod ecyl-Con ta in in g 16-m er 46. 42 (0.82 g, 0.35 mmol),

44 (0.68 g, 0.30 mmol), THF (10 mL), bis(dibenzylideneac-

etone)palladium(0) (0.020 g, 0.035 mmol), triphenylphosphine

(0.046 g, 0.18 mmol), copper(I) iodide (0.0070 g, 0.035 mmol),

and N,N-diisopropylethylamine (0.49 mL, 2.80 mmol) for 4 d

at 65 °C afforded 1.20 g (90%) of the title compound as a yellow

solid after flash liquid chromatography (3:1; hexane:dichlo-

romethane). R_f) 0.64 (3:1; hexane:dichloromethane). IR

(KBr) 2924, 2854, 2199, 2150, 1593, 1502, 1460, 1402, 1345,

cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.49-7.44 (m, 4 H), 7.40-

.

7.31 (m, 7 H), 7.29-7.25 (m, 1 H), 3.77 (q, J ) 7.1 Hz, 4 H),

3.33 (s, 1 H), 2.90 (m, 6 H), 2.80 (t, J ) 7.1 Hz, 2 H), 1.75-

1.67 (m, 8 H), 1.43-1.26 (m, 78 H), 0.90-0.87 (m, 12 H). ¹³C

NMR (100 MHz, CDCl₃) δ 151.20, 146.00, 145.74, 145.21,

145.11, 132.86, 132.15, 132.10, 131.73, 131.62, 128.74, 128.61,

123.99, 123.70, 123.44, 122.43, 121.98, 121.60, 121.15, 118.79,

117.60, 94.34, 92.66, 90.83, 89.89, 89.66, 82.15, 35.04, 34.72,

34.37, 32.00, 30.91, 30.71, 30.51, 29.80, 29.78, 29.76, 29.74,

29.69, 29.66, 29.64, 29.52, 29.45, 29.43, 22.75, 14.17. LRMS

calcd for C₈₄H₁₂₃N₃: 1174 (100%), 1175 (98%), 1176 (47%).

Found: 1174 (100%), 1175 (50%), 1176 (33%).

1235, 1096, 888, 838, 723, 658, 612 cm^-^{1 1}H NMR (400 MHz,

.

CDCl₃) δ 7.50-7.46 (m, 16 H), 7.38 (m, 16 H), 7.31-7.27 (m,

16 H), 3.77 (q, J ) 7.1 Hz, 4 H), 2.84 (m, 32 H), 1.71 (m, 32

H), 1.23 (m, 288 H), 0.85-0.83 (m, 48 H), 0.25 (s, 9 H). ¹³C

NMR (125 MHz, CD₂Cl₂) δ 151.77, 146.44, 146.23, 145.75,

145.44, 136.24, 135.28, 134.84, 134.72, 133.80, 133.15, 132.54,

132.15, 131.23, 130.74, 130.45, 130.14, 129.87, 129.17, 128.97,

128.74, 128.63, 127.61, 127.48, 127.14, 126.58, 126.09, 125.85,

124.96, 124.40, 124.24, 123.72, 123.11, 122.68, 122.48, 121.50,

119.05, 118.02, 95.14, 93.07, 90.05, 41.17, 39.88, 39.71, 39.48,

39.31, 38.51, 38.12, 37.84, 37.55, 37.24, 37.09, 36.96, 36.40,

36.16, 35.41, 35.11, 34.90, 34.75, 34.14, 33.85, 33.51, 33.25,

32.86, 32.43, 31.82, 31.38, 31.15, 30.87, 30.19, 30.07, 29.88,

29.41, 29.02, 28.67, 28.45, 28.35, 27.89, 26.78, 27.60, 27.23,

26.81, 26.35, 25.19, 25.70, 24.24, 24.13, 23.17, 22.91, 20.60,

20.31, 19.95, 19.48, 18.47, 14.66, 14.39, 11.67, 11.23, 0.10.

N-E t h yl-N-(h yd r oxyet h yl)-4-t r ia zen yl-2-d od ecyla ce-

top h en on e. To a 3000 mL round-bottom flask equipped with

a mechanical stirrer, nitrogen inlet, and 0 °C condenser,

containing boron trifluoride etherate (102.35 mL, 832.20 mmol)

at 0 °C, was added 11 (129.31 g, 426.77 mmol) in dichlo-

romethane (1.5 L) followed by tert-butyl nitrite (83.75 mL,

704.17 mmol). The reaction was stirred for 30 min at 0 °C

before potassium carbonate (277.22 g, 2.06 mol) and 2-(ethyl-

amino)ethanol (262.22 mL, 2.69 mol) were added sequentially.

The reaction was then warmed to room temperature over 2 d

before water (450 mL) was added in three portions. The

potassium carbonate was then filtered and the solvent removed

in vacuo before the organic layer was extracted with dichlo-

romethane and dried over magnesium sulfate. The sample

was concentrated in vacuo yielding a crude oil that was

purified by flash liquid chromatography (4:1; hexane:ethyl

acetate) to afford 146.43 g (85%) of the title compound as a

brown oil. R_f) 0.22 (3:1; hexane:ethyl acetate). IR (neat)

3439, 2927, 2853, 1678, 1600, 1557, 1454, 1430, 1395, 1349,

Dod ecyl-Con ta in in g Octa m er 40. 34 (1.88 g, 1.47 mmol),

37 (1.73 g, 1.47 mmol), THF (8 mL), bis(dibenzylideneacetone)-

palladium(0) (0.042 g, 0.074 mmol), triphenylphosphine (0.097

g, 0.37 mmol), copper(I) iodide (0.029 g, 0.15 mmol), and N,N-

diisopropylethylamine (1.02 mL, 5.88 mmol) for 3 d afforded

1.62 g (48%) of the title compound as a yellow solid after flash

liquid chromatography (8:1; hexane:dichloromethane). R_f)

0.12 (8:1; hexane:dichloromethane). IR (KBr) 2922, 2851,

2199, 2149, 1594, 1503, 1460, 1402, 1348, 1235, 1096, 835, 722,

643 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.49-7.42 (m, 8 H),

.

7.40-7.38 (m, 4 H), 7.36-7.25 (m, 12 H), 3.77 (q, J ) 7.1 Hz,

4 H), 2.87-2.75 (m, 16 H), 1.73-1.64 (m, 16 H), 1.54-1.25

(m, 150 H), 0.89-0.85 (m, 24 H), 0.27 (s, 9 H). ¹³C NMR (125

MHz, CDCl₃) δ 151.60, 146.39, 146.14, 146.11, 145.61, 145.51,

145.31, 133.25, 132.76, 132.54, 132.49, 132.12, 132.02, 132.00,

131.91, 131.77, 129.15, 129.00, 128.96, 124.37, 124.09, 123.83,

123.79, 123.68, 123.64, 123.04, 123.02, 122.92, 122.83, 122.69,

122.38, 121.98, 121.53, 119.18, 117.98, 104.02, 100.10, 95.07,

95.00, 94.71, 93.03, 91.20, 90.27, 90.04, 89.94, 82.55, 82.48,

35.41, 35.10, 34.75, 32.36, 31.26, 31.08, 30.99, 30.88, 30.15,

30.14, 30.13, 30.11, 30.08, 30.06, 30.02, 30.00, 29.96, 29.89,

29.81, 29.78, 23.12, 14.53, 0.37.

Dod ecyl-Con ta in in g Iod id e Octa m er 42 fr om 40. 40

(0.81 g, 0.35 mmol) and iodomethane (5 mL) afforded 0.82 g

(100%) of the title compound as a yellow solid. R_f) 0.29 (9:1;

hexane:dichloromethane). IR (KBr) 3028, 2924, 2853, 2201,

2151, 1923, 1849, 1775, 1744, 1708, 1656, 1588, 1502, 1461,

1382, 1307, 1255, 1084, 886, 839, 723 cm^-1

.

¹H NMR (500

1243, 1130, 1074, 951, 896, 825, 721, 624 cm^-^{1 1}H NMR (400

.

MHz, CDCl₃) δ 7.59 (d, J ) 1.0 Hz, 1 H), 7.51 (d, J ) 1.3 Hz,

1 H), 7.49-7.46 (m, 5 H), 7.42-7.25 (m, 16 H), 7.19 (d, J )

8.1 Hz, 1 H), 2.90-2.70 (m, 16 H), 1.74-1.66 (m, 16 H), 1.45-

1.25 (m, 144 H), 0.89-0.86 (m, 24 H), 0.28 (s, 9 H). ¹³C NMR

MHz, CDCl₃) δ 7.65 (d, J ) 8.9 Hz, 1 H), 7.26-7.25 (m, 2 H),

3.88-3.86 (m, 5 H), 2.87 (t, J ) 8.0 Hz, 2 H), 2.55 (s, 3 H),

1.55 (m, 2 H), 1.40-1.20 (m, 23 H), 0.86 (t, J ) 7.0 Hz, 3 H).

¹³C NMR (100 MHz, CDCl₃) δ 200.66, 153.10, 145.14, 133.74,

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1405

131.10, 123.35, 117.00, 60.80, 51.13, 34.59, 31.87, 31.73, 29.85,

29.64, 29.51, 29.39, 29.31, 22.63, 14.07. HRMS calcd for

C₂₄H₄₁N₃O₂: 403.3199. Found: 403.3206.

compound as a brown oil which was analytically identical to

the titled material prepared from 13.

P olym er -Su p p or ted Mon om er 50. A three-neck 2 L

round-bottomed flask equipped with a mechanical stirrer and

a water condenser was charged with chloromethyl polystyrene

(50.00 g, 50.00 mmol, 1.00 ( 0.05 mequiv g^-1, 1% cross-linked

with divinylbenzene, 200-400 mesh). The vessel was flushed

thoroughly with nitrogen before a solution of anchor 49 (57.75

g, 150 mmol) in dry THF (250 mL) was added via a cannula

followed by additional dry THF (350 mL) to facilitate free

stirring. The reaction mixture was cooled to -78 °C, and

sodium hydride (5.62 g, 140.50 mmol, 60% dispersion in oil)

was added carefully in portions under a nitrogen blanket. After

the addition was complete, the reaction mixture was warmed

to room temperature over 30 min and then heated at 75 °C

for 48 h with gentle stirring. The mixture was then cooled to

0 °C, quenched with methanol (60 mL) and water (60 mL),

and filtered. The polymer was then transferred to a pre-

weighed fritted filter using dichloromethane, and washed

sequentially (ca. 3 × 30 mL/g polymer) with the following:

THF, H₂O, MeOH, EtOAc, n-hexane, CH₂Cl₂, and MeOH, and

dried to constant mass in a vacuum oven at 40 °C to afford

67.95 g (∆W_theor) 17.41 g, ∆W ) 17.95 g) of the title polymer

as yellow beads. IR (CCl₄) 3305, 3025, 2937, 2869, 2504, 2403,

2289, 2211, 2098, 1944, 1873, 1803, 1745, 1593, 1558, 1446,

1366, 1237, 1197, 1081, 1023, 893, 775 cm^-1. Gel-phase ¹³C

NMR showed some remaining benzylic chloride peak at δ

46.77. Anal. Calcd for the functionalized resin: C, 87.61; H,

8.21; Cl, 0.64; N, 2.55; O, 0.97. Found: C, 87.12; H, 8.30; Cl,

0.61; N, 2.56. This signifies that 77% of the chloride was

substituted. All subsequent calculated elemental composition

data reflect this initial substitution.

N-E t h yl-N-[(t r im et h ylsiloxy)et h yl]-4-t r ia zyl-2-d od ec-

yla cetop h en on e (47). To a solution of N-ethyl-N-(hydroxy-

ethyl)-4-triazenyl-2-dodecynylacetophenone (1.99 g, 4.94 mmol)

in THF (20 mL) was added dropwise triethylamine (4.13 mL,

29.64 mmol) at room temperature. The mixture was allowed

to stir for 10 min before chlorotrimethylsilane (1.88 mL, 14.82

mmol) was added slowly. The resulting reaction mixture was

allowed to stir for 1 d before being poured into water. The

organic layer was extracted with ether and dried over mag-

nesium sulfate. The sample was concentrated in vacuo to

afford 2.23 g (95%) of the title compound as a brown oil which

was taken on to the next step without purification. R_f) 0.61

(9:1; hexane:ether). IR (neat) 2927, 2857, 1679, 1598, 1559,

1454, 1532, 1388, 1348, 1246, 1200, 1101, 944, 843, 752, 720,

620 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.66 (d, J ) 9.0 Hz,

.

1 H), 7.25-7.23 (m, 2 H), 3.84-3.82 (m, 5 H), 2.87 (t, J ) 7.9

Hz, 2 H), 2.55 (s, 3 H), 1.56 (p, J ) 7.0 Hz, 2 H), 1.26-1.23

(m, 22 H), 0.86 (t, J ) 7.0 Hz, 3 H), 0.095 (s, 9 H). ¹³C NMR

(100 MHz, CDCl₃) δ 200.32, 153.14, 145.10, 133.72, 131.04,

123.45, 117.09, 60.21, 58.33, 45.80, 34.63, 31.91, 31.75, 29.87,

29.68, 29.66, 29.64, 29.55, 29.49, 29.35, 22.67, 14.09, -0.60.

HRMS calcd for C₂₇H₄₉N₃O₂Si: 475.3594. Found: 475.3589.

N-Eth yl-N-[(tr im eth ylsiloxy)eth yl]-1-tr ia zyl-3-d od ecyl-

4-[(tr im eth ylsilyl)eth yn yl]ben zen e (48). To a stirred solu-

tion of diisopropylamine (0.88 mL, 6.70 mmol) in THF (5 mL)

was added at -78 °C, under nitrogen, n-butyllithium (3.90 mL,

6.08 mmol, 1.56 M in hexanes). The reaction mixture was

allowed to warm to 0 °C for 10 min and then cooled to -78 °C.

To the LDA solution was added triazene 47 (2.31 g, 4.86 mmol)

in THF (5 mL). The reaction mixture was stirred at -78 °C

for 1 h before adding, at the same temperature, diethyl

chlorophosphonate (0.88 mL, 6.08 mmol). The reaction mix-

ture was allowed to warm to room temperature over 30 min

before being recooled to -78 °C. The reaction solution was

then transferred via cannula into 2.25 equiv of LDA [made as

above with diisopropylamine (1.58 mL, 12.04 mmol) and

n-butyllithium (7.01 mL, 10.94 mmol, 1.56 M in hexanes)] in

THF (15 mL) at -78 °C. The ensuing reaction mixture was

allowed to warm to 0 °C over 1 h and then recooled to -78 °C

before chlorotrimethylsilane (1.54 mL, 12.15 mmol) was added.

The solution was allowed to warm to room temperature

overnight before being poured into water and extracted with

ether (3×). The combined ether extracts were washed with

brine and dried over magnesium sulfate. Filtration and

removal of the solvent in vacuo afforded 2.83 g of the title

compound as a brown oil which was used directly for the next

step. IR (neat) 2926, 2855, 2150, 1602, 1454, 1401, 1378, 1348,

1289, 1251, 1198, 1159, 1094, 978, 940, 842, 758, 721, 697,

Gen er a l P r oced u r e for th e Cou p lin g of a P olym er -

Su p p or ted Ter m in a l Alk yn e w ith a n Ar yl Ha lid e.⁵

A

thick-walled oven-dried screw cap tube was charged with the

polymer-supported terminal alkyne (1.0 equiv) and the mon-

omeric or oligomeric aryl iodide (2.0 equiv). To the reaction

flask was added, via cannula, the supernatant of a premade

solution (6 mL/g of polymer) of bis(dibenzylideneacetone)-

palladium(0) (4 mol %), triphenylphosphine (20 mol %), and

copper(I) iodide (4 mol %) in dry triethylamine which had been

degassed and stirred at 70 °C for 2 h. The tube was flushed

with nitrogen, capped, and kept at 65 °C for 12-48 h without

stirring, and the vessel was shaken periodically. The polymer

was then poured onto a preweighed fritted filter using dichlo-

romethane to wash the beads that were sticking to the sides

of the flask. The beads were then washed sequentially (ca.

30 mL/g of polymer) with the following: CH₂Cl₂, DMF, 0.05

M solution of sodium diethyl dithiocarbamate in 99/1 DMF/

diisopropylethylamine,¹⁹DMF, CH₂Cl₂, MeOH, and dried to

constant mass in a vacuum oven at 60 °C. The degree of

substitution of each reaction was estimated by infrared

analysis of the polymer bound substrate. Absorptions at 3311

cm^-1(strong) and 2109 cm^-1(weak) were characteristic of

the terminal alkynyl carbon-hydrogen and carbon-carbon

stretches, respectively, and an absorption at 2156 cm^-1(strong)

was characteristic of the carbon-carbon stretch of the tri-

methylsilyl-protected terminal alkyne.¹³The excess aryl

halide was recovered from the washings and repurified before

further use. The amount of aryl iodide recovered after

purification was generally ca. 30% less than expected.

P olym er -Su p p or ted Silyl Dim er 51. 16 (33.72 g, 72.05

mmol), 50 (59.07 g, 36.03 mmol, 0.61 mmol g^-1), bis(diben-

zylideneacetone)palladium(0) (1.65 g, 2.88 mmol), triphen-

ylphosphine (3.78 g, 14.41 mmol), copper(I) iodide (0.55 g, 2.88

mmol), and triethylamine (500 mL) for 2 d afforded 69.05 g

(∆W_theor) 12.25 g, ∆W ) 9.98 g) of the title polymer as yellow

beads. IR (CCl₄) 3062, 3027, 2952, 2914, 2853, 2291, 2201,

2150, 2009, 1943, 1873, 1803, 1746, 1663, 1595, 1549, 1491,

1447, 1345, 1244, 1196, 1156, 1093, 1008, 981, 790, 707, 627

cm^-1. Gel-phase ¹³C NMR showed the gain of a trimethylsilyl

peak at δ 0.47. Anal. Calcd for the functionalized resin: C,

86.51; H, 8.63; Cl, 0.53; N, 2.11; O, 0.80; Si, 1.41. Found: C,

86.12; H, 8.66; N, 2.31.

654 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.36 (d, J ) 8.2 Hz,

1 H), 7.19 (s, 1 H), 7.16 (d, J ) 8.2 Hz, 1 H), 3.80-3.78 (m, 4

H), 2.74 (t, J ) 8.0 Hz, 2 H), 1.63 (m, 2 H), 1.24-1.14 (m, 23

H), 0.86 (t, J ) 6.9 Hz, 3 H), 0.23 (s, 9 H), 0.090 (s, 9 H).

HRMS calcd for C₃₀H₅₅N₃OSi₂: 529.3884. Found: 529.3892.

N-E t h yl-N-[(h yd r oxyet h yl)et h yl]-1-t r ia zyl-3-d od ecyl-

4-eth yn ylben zen e (49). 48 (2.83 g, 4.86 mmol), methanol

(10 mL), dichloromethane (10 mL), potassium carbonate (4.15

g, 30 mmol), and gravity liquid chromatography (3:1; hexane:

ethyl acetate) afforded 0.94 g (50% over two steps) of the title

compound as a brown oil. R_f) 0.34 (3:1; hexane:ethyl acetate).

IR (neat) 3415, 3313, 2925, 2855, 2100, 1740, 1600, 1560, 1452,

1434, 1400, 1378, 1345, 1239, 1181, 1152, 1101, 1078, 1048,

892, 829, 791, 721, 643 cm^-1

.

¹H NMR (400 MHz, CDCl₃) δ

7.40 (d, J ) 8.2 Hz, 1 H), 7.21 (d, J ) 1.9 Hz, 1 H), 7.18 (dd,

J ) 8.2, 1.2 Hz, 1 H), 3.87-3.81 (m, 5 H), 3.22 (s, 1 H), 2.76 (t,

J ) 8.0 Hz, 2 H), 1.63 (p, J ) 7.0 Hz, 2 H), 1.32-1.23 (m, 23

H), 0.86 (t, J ) 7.0 Hz, 3 H). ¹³C NMR (100 MHz, CDCl₃) δ

150.22, 146.53, 133.55, 120.98, 118.56, 117.43, 82.82, 80.44,

61.28, 51.59, 34.64, 31.96, 30.68, 29.73 (2 C), 29.69, 29.65,

29.56, 29.52, 29.40, 22.72, 14.15. HRMS calcd for C₂₄H₃₉N₃O:

385.3093. Found: 385.3087.

1-Iodo-3-dodecyl-4-[(tr im eth ylsilyl)eth yn yl]ben zen e (16)

P r ep a r ed fr om 48. 48 (6.62 g, 12.5 mmol) and iodomethane

(10 mL) afforded 2.83 g (60% over two steps) of the title

(19) Briscoe, G. B.; Humphries, S. Talanta 1969, 16, 1403.

1406 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

Gen er a l P r oced u r e for th e Liber a tion of P olym er -

Su p p or ted Oligom er s.⁵A thick-walled oven-dried screw cap

tube was charged with a suspension of the polymer-supported

oligomer and iodomethane (7 mL/g of polymer). The tube was

flushed with nitrogen, capped, and heated to 120 °C for 12-

24 h without stirring. The reaction mixture was cooled and

passed through a fritted filter before the resin was introduced

to hot CH₂Cl₂(3×) to extract any residual product trapped in

the polymer matrix. The combined filtrate was then passed

through a plug of silica gel with CH₂Cl₂.

Dod ecyl-Con ta in in g Iod id e Dim er 25 fr om 51. 51

(45.72 g, 23.31 mmol, 0.51 mmol g^-1) and iodomethane (320

mL) afforded 14.66 g (86%) of the title compound as a light

brown oil which was analytically identical to the titled material

prepared from 22.

Gen er a l P r oced u r e for th e Desilyla tion of P olym er -

Su p p or ted Silyla ted Alk yn es.⁵To a suspension of polymer-

supported aryl (trimethylsilyl)alkyne (1.0 equiv) and THF (9

mL/g of polymer) in an Erlenmeyer flask was added a solution

of TBAF (2.0 equiv, 1.0 M in THF). The suspension was

swirled periodically for 15 min. The polymer was then

transferred to a preweighed fritted filter using THF, washed

sequentially (ca. 30 mL/g polymer) with THF followed by

MeOH, and dried to constant mass in a vacuum oven at 60

°C. The efficiency of each reaction was estimated by infrared

analysis of the polymer bound substrate. An absorption at

3311 cm^-1(strong) and 2109 cm^-1(weak) are characteristic of

the terminal alkynyl carbon-hydrogen and carbon-carbon

stretches, respectively, and an absorption at 2156 cm^-1(strong)

is characteristic of the carbon-carbon stretch of the trimeth-

ylsilyl-protected alkyne.¹⁹

P olym er -Su p p or ted Ter m in a l Alk yn yl Dim er 52. 51

(22.87 g, 11.66 mmol, 0.51 mmol g^-1), THF (206 mL), and

TBAF (6.96 mL, 24.00 mmol, 1.00 M in THF) afforded 22.09 g

(∆W_theor) -0.84 g, ∆W ) -0.78 g) of the title polymer as

goldish yellow beads. IR (CCl₄) 3307, 3083, 3061, 3027, 2935,

2851, 2201, 2102, 1941, 1869, 1802, 1746, 1663, 1600, 1548,

1493, 1452, 1401, 1377, 1345, 1238, 1194, 1154, 1094, 1027,

1005, 979, 892, 804, 699, 648, 609 cm^-1. Gel-phase ¹³C NMR

showed the loss of a trimethylsilyl peak at δ 0.47. Anal. Calcd

for the functionalized resin: C, 87.89; H, 8.53; Cl, 0.55; N, 2.19;

O, 0.83. Found: C, 87.94; H, 8.49; N, 2.31.

∆W ) 1.71 g) of the title polymer as rusty orange beads. IR

(CCl₄) 3061, 3027, 2917, 2198, 2151, 1941, 1871, 1802, 1745,

1660, 1596, 1548, 1498, 1451, 1402, 1345, 1247, 1195, 1154,

1094, 1006, 980, 892, 794, 703 cm^-1

.

Gel-phase ¹³C NMR

showed the gain of a trimethylsilyl peak at δ 0.36. Anal.

Calcd for the functionalized resin: C, 87.84; H, 9.47; Cl, 0.29;

N, 1.17; O, 0.44; Si, 0.78. Found: C, 87.56; H, 9.00; N, 1.44.

Dod ecyl-Con ta in in g Iod id e Octa m er 42 fr om 55. 55

(4.78 g, 1.34 mmol, 0.28 mmol g^-1) and iodomethane (35 mL)

afforded 2.51 g (80%) of the title compound as a waxy yellow

solid which was analytically identical to the titled material

prepared from 40.

P olym er -Su p p or ted Ter m in a l Alk yn yl Octa m er 56. 55

(1.90 g, 0.53 mmol, 0.28 mmol g^-1), THF (20 mL), and TBAF

(0.31 mL, 1.06 mmol, 1.00 M in THF) afforded 1.93 g (∆W_theor

) -0.04 g, ∆W ) 0.03 g) of the title polymer as rusty orange

beads. IR (CCl₄) 3308, 3061, 3027, 2923, 2855, 2198, 2103,

1943, 1870, 1799, 1772, 1740, 1696, 1652, 1594, 1547, 1498,

1455, 1399, 1343, 1242, 1197, 1154, 1090, 1007, 891, 793, 706

cm^-1. Gel-phase ¹³C NMR showed the loss of a trimethylsilyl

peak at δ 0.36. Anal. Calcd for the functionalized resin: C,

88.62; H, 9.44; Cl, 0.30; N, 1.22; O, 0.45. Found: C, 87.93; H,

8.92; N, 1.49.

P olym er -Su p p or ted Dod ecyl-Con ta in in g 16-m er 57.

42 (2.18 g, 0.93 mmol), 56 (1.53 g, 0.44 mmol, 0.29 mmol g^-1),

bis(dibenzylideneacetone)palladium(0) (0.021 g, 0.037 mmol),

triphenylphosphine (0.050 g, 0.19 mmol), copper(I) iodide

(0.0070 g, 0.037 mmol), and triethylamine (40 mL) afforded

1.76 g (∆W_theor) 0.98 g, ∆W ) 0.23 g) of the title polymer as

rusty orange beads. IR (CCl₄) 3061, 3027, 2923, 2855, 2198,

2151, 1942, 1869, 1798, 1772, 1740, 1696, 1675, 1652, 1594,

1545, 1499, 1455, 1401, 1343, 1244, 1195, 1152, 1088, 1007,

889, 793, 706 cm^-1. Gel-phase ¹³C NMR showed the gain of a

trimethylsilyl peak at δ 0.36. Anal. Calcd for the function-

alized resin: C, 88.46; H, 9.86; Cl, 0.18; N, 0.73; O, 0.28; Si,

0.49. Found: C, 86.95; H, 9.08; N, 1.30.

Dod ecyl-Con ta in in g Iod id e 16-m er 58. 57 (1.37 g, 0.23

mmol, 0.17 mmol g^-1) and iodomethane (25 mL) afforded 0.84

g (79%) of the title compound as a waxy yellow solid. R_f)

0.27 (9:1; hexane:dichloromethane). IR (KBr) 2924, 2855,

2146, 1590, 1502, 1461, 1384, 1262, 1088, 888, 837, 724, 618

cm^-1

.

¹H NMR (500 MHz, CDCl₃) δ 7.58 (br s, 2 H), 7.50-

P olym er -Su p p or ted Silyl Tetr a m er 53. 25 (13.73 g,

18.65 mmol), 52 (17.28 g, 8.99 mmol, 0.52 mmol g^-1), bis-

(dibenzylideneacetone)palladium(0) (0.43 g, 0.75 mmol), tri-

phenylphosphine (0.98 g, 3.75 mmol), copper(I) iodide (0.14 g,

0.75 mmol), and triethylamine (200 mL) for 1 d afforded 21.71

g (∆W_theor) 5.47 g, ∆W ) 4.43 g) of the title polymer as

mustard-colored beads. IR (CCl₄) 3061, 3026, 2919, 2853,

2198, 2151, 1940, 1867, 1800, 1746, 1660, 1600, 1548, 1493,

1453, 1402, 1378, 1344, 1250, 1194, 1154, 1093, 1028, 1005,

979, 891, 792, 700 cm^-1. Gel-phase ¹³C NMR showed the gain

of a trimethylsilyl peak at δ 0.40. Anal. Calcd for the

functionalized resin: C, 87.14; H, 9.03; Cl, 0.42; N, 1.66; O,

0.63; Si, 1.11. Found: C, 86.89; H, 8.97; N, 1.82.

Dod ecyl-Con ta in in g Iod id e Tetr a m er 34 fr om 53. 53

(14.47 g, 5.79 mmol, 0.40 mmol g^-1) and iodomethane (100 mL)

afforded 6.02 g (77%) of the title compound as a light brown

oil which solidified upon standing and was analytically identi-

cal to the titled material prepared from 31.

P olym er -Su p p or t ed Ter m in a l Alk yn yl Tet r a m er 54.

53 (6.88 g, 2.75 mmol, 0.40 mmol g^-1), THF (62 mL), and TBAF

(1.60 mL, 5.50 mmol, 1.00 M in THF) afforded 6.80 g (∆W_theor

) -0.20 g, ∆W ) -0.08 g) of the title polymer as orange beads.

IR (CCl₄) 3308, 3061, 3027, 2920, 2853, 2198, 2102, 1941, 1870,

1802, 1745, 1662, 1596, 1550, 1495, 1450, 1401, 1375, 1345,

1239, 1195, 1155, 1092, 1007, 980, 892, 795, 702 cm^-1. Gel-

phase ¹³C NMR showed the loss of a trimethylsilyl peak at δ

0.40. Anal. Calcd for the functionalized resin: C, 88.24; H,

8.97; Cl, 0.43; N, 1.71; O, 0.65. Found: C, 86.13; H, 8.44; N,

1.88.

7.47 (m, 12 H), 7.40-7.30 (m, 32 H), 7.19 (d, J ) 8.0 Hz, 2 H),

2.90-2.70 (m, 32 H), 1.80-1.60 (m, 32 H), 1.40-1.20 (m, 288

H), 0.88-0.86 (m, 48 H), 0.27 (s, 9 H). ¹³C NMR (125 MHz,

CDCl₃) δ 152.57, 147.51, 145.61, 145.41, 138.19, 135.60, 135.23,

133.84, 136.76, 132.56, 132.14, 131.90, 129.16, 128.78, 125.95,

125.46, 123.65, 123.54, 123.06, 122.54, 107.71, 95.19, 95.09,

95.08, 95.05, 95.02, 94.97, 94.60, 94.59, 94.58, 94.57, 94.55,

90.15, 90.05, 90.02, 89.95, 89.93, 89.39, 89.37, 46.73, 46.41,

44.43, 42.73, 41.80, 41.09, 40.62, 40.52, 39.92, 39.86, 39.81,

39.50, 39.45, 39.29, 38.85, 38.17, 37.93, 37.88, 37.84, 37.82,

37.80, 37.73, 37.53, 37.42, 37.38, 37.09, 36.92, 36.71, 36.57,

36.07, 36.02, 35.77, 35.51, 35.12, 34.94, 34.83, 34.14, 33.90,

33.84, 33.65, 33.53, 33.33, 33.20, 33.18, 32.91, 32.83, 32.79,

32.70, 32.64, 32.38, 32.37, 32.08, 31.42, 31.09, 30.59, 30.47,

30.18, 30.14, 30.10, 30.02, 29.93, 29.90, 29.83, 29.80, 29.41,

29.26, 29.00, 28.48, 28.40, 27.96, 27.86, 27.74, 27.52, 27.22,

27.18, 27.14, 26.90, 26.83, 26.57, 267.34, 25.88, 25.62, 25.23,

24.90, 24.29, 24.11, 23.92, 23.85, 23.60, 23.48, 23.13, 23.08,

23.04, 22.04, 20.71, 20.57, 20.22, 20.16, 20.11, 19.68, 19.64,

19.13, 18.11, 14.97, 14.83, 14.54, 12.86, 11.82, 11.30, 8.11, 7.94,

7.89, 0.37. Anal. Calcd for C₃₂₃H₄₅₇ISi: C, 86.31; H, 10.25.

Found: C, 85.92; H, 10.76. M_n) 8860, M_w) 10,940, M_w/M_n

) 1.23. λ (THF) ) 240, 377 (ꢀ 3.59 × 10⁵M^-1cm^-1) nm. Emiss

(THF) ) 414, 436 nm.

1-(P h en yleth yn yl)-4-(th ioa cetyl)ben zen e (61). 59 (0.36

g, 1.30 mmol), phenylacetylene (0.16 mL, 1.43 mmol), bis-

(dibenzylideneacetone palladium(0) (37.31 mg, 0.070 mmol),

triphenylphosphine (85.20 mg, 0.33 mmol), copper(I) iodide

(24.80 mg, 0.13 mmol), N,N-diisopropylethylamine (0.90 mL,

5.20 mmol), and THF (3 mL) for 2 d afforded 0.31 g (95%) of

the title compound as a yellow solid after gravity liquid

chromatography (24:1; hexane:ether). R_f) 0.26 (24:1; hexane:

ether). IR (KBr) 1699, 1587, 1493, 1442, 1396, 1352, 1314,

P olym er -Su p p or ted Silyl Octa m er 55. 34 (5.70 g, 4.48

mmol), 54 (5.46 g, 2.24 mmol, 0.41 mmol g^-1), bis(dibenzylide-

neacetone)palladium(0) (0.10 g, 0.18 mmol), triphenylphos-

phine (0.23 g, 0.90 mmol), copper(I) iodide (0.034 g, 0.18 mmol),

and triethylamine (60 mL) afforded 7.17 g (∆W_theor) 2.56 g,

1

1211, 1175, 1112, 1012, 944, 877, 826, 756, 690, 622 cm^-1. H

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1407

NMR (300 MHz, CDCl₃) δ 7.54 (d, J ) 8.5 Hz, 2 H), 7.53 (dd,

J ) 5.5, 2.4 Hz, 2 H), 7.38 (d, J ) 8.5 Hz, 2 H), 7.36-7.33 (m,

3 H), 2.42 (s, 3 H). ¹³C NMR (125 MHz, CDCl₃) δ 193.31,

134.16, 132.12, 131.65, 128.50, 128.35, 128.03, 124.52, 122.89,

91.04, 88.60, 30.21. HRMS calcd for C₁₆H₁₂OS: 252.0609.

Found: 252.0607. λ (CH₂Cl₂) ) 228, 293, 309 nm.

worked up in the same manner as above. Eluents and other

slight modifications are described below for each material.

Tr im er Th iol 64. 63 (0.19 g, 0.50 mmol), sodium hydroxide

(40 mg, 1.0 mmol), zinc dust (5.0 mg, 0.076 mequiv), water (3

mL), THF (5 mL), and 3 M hydrochloric acid (0.33 mL) afforded

0.16 g (92%) of the title compound as a yellow solid with slight

impurities. R_f) 0.44 (9:1; hexane:ethyl acetate). IR (neat)

2963, 2929, 2869, 2562, 2204, 1722, 1654, 1598, 1499, 1460,

2-E t h yl-4-(p h en ylet h yn yl)-1-(t r im et h ylsilyet h yn yl)-

ben zen e (62). 14 (0.98 g, 3 mmol), phenylacetylene (0.36 mL,

3.30 mmol), bis(dibenzylideneacetone)palladium(0) (86.10 mg,

0.15 mmol), triphenylphosphine (196.70 mg, 3.30 mmol),

copper(I) iodide (57.10 mg, 0.30 mmol), N,N-diisopropyleth-

ylamine (2.10 mL, 12 mmol), and THF (6 mL) for 6 d afforded

0.89 g (98%) of the title compound as a yellow oil after gravity

liquid chromatography (hexane). R_f) 0.39 (hexane). IR (neat)

3061, 2967, 2874, 2246, 2152, 1602, 1496, 1458, 1444, 1407,

1380, 1250, 1222, 1115, 1068, 1026, 909, 860, 756, 734, 690,

1400, 1271, 1118, 1015, 893, 824, 756, 691, 619 cm^-^{1 1}H NMR

.

(300 MHz, CDCl₃) δ 7.52 (d, J ) 7.8 Hz, 2 H), 7.51 (dd, J )

7.5, 2.1 Hz, 1 H), 7.43 (d, J ) 7.9 Hz, 1 H), 7.40 (s, 1 H), 7.36

(d, J ) 8.4 Hz, 2 H), 7.34 (dd, J ) 8.1, 3.4 Hz, 1 H), 7.33 (d, J

) 7.9 Hz, 2 H), 7.23 (d, J ) 7.5 Hz, 2 H), 3.52 (s, 1 H), 2.85 (q,

J ) 7.6 Hz, 2 H), 1.29 (t, J ) 7.5 Hz, 3 H). ¹³C NMR (125

MHz, CDCl₃) δ 168.18, 146.57, 132.92, 132.47, 132.45, 132.41,

132.07, 131.54, 131.32, 129.43, 129.34, 129.24, 129.12, 128.82,

94.55, 91.32, 89.94, 88.83, 28.06, 15.01. LRMS Calcd for

C₂₄H₁₈S: 338. Found: 338. λ (CH₂Cl₂) ) 228, 234, 282, 339

nm.

626 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.53-7.50 (m, 2 H),

.

7.38 (d, J ) 7.9 Hz, 1 H), 7.36 (s, 1 H), 7.35-7.32 (m, 3 H),

7.27 (dd, J ) 7.9, 1.7 Hz, 1 H), 2.78 (q, 7.6 Hz, 2 H), 1.25 (t, J

) 7.6 Hz, 3 H), 0.25 (s, 9 H). ¹³C NMR (125 MHz, CDCl₃) δ

147.19, 132.91, 132.17, 131.57, 129.37, 128.91, 128.90, 124.07,

123.75, 122.84, 104.19, 100.24, 91.54, 90.06, 28.18, 14.99, 0.54.

2-Eth yl-1,4-bis[(tr im eth ylsilyl)eth yn yl]ben zen e (65).

14 (0.98 g, 3.0 mmol), (trimethylsilyl)acetylene (0.47 mL, 3.30

mmol), bis(dibenzylideneacetone)palladium(0) (86.10 mg, 0.15

mmol), triphenylphosphine (0.20 g, 0.75 mmol), copper(I) iodide

(57.10 mg, 0.30 mmol), N,N-diisopropylethylamine (2.10 mL,

12 mmol), and THF (6 mL) for 1 d afforded 0.83 g (93%) of the

title compound as a yellow oil after gravity liquid chromatog-

raphy (hexane). R_f) 0.55 (hexane). IR (neat) 2963, 2935,

2899, 2875, 2157, 1602, 1484, 1458, 1406, 1250, 1213, 1120,

3-Eth yl-1-(p h en yleth yn yl)-4-eth yn ylben zen e. 62 (0.89

g, 2.95 mmol), methanol (15 mL) and potassium carbonate

(1.24 g, 9 mmol) afforded 0.63 g (93%) of the title compound

as a yellow oil. IR (neat) 3293, 3059, 2969, 2933, 2874, 2100,

1603, 1495, 1458, 1443, 1241, 1066, 1026, 912, 894, 831, 756,

689, 600 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.53-7.50 (m, 2

.

916, 859, 760, 700, 628 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ

H), 7.42 (d, J ) 7.9 Hz, 1 H), 7.38 (s, 1 H), 7.36-7.32 (m, 3 H),

7.29 (dd, J ) 7.9, 1.6 Hz, 1 H), 3.32 (s, 1 H), 2.81 (q, J ) 7.6

Hz, 2 H), 1.25 (t, J ) 7.6 Hz, 3 H). ¹³C NMR (125 MHz, CDCl₃)

δ 147.32, 133.34, 133.02, 132.16, 131.57, 129.33, 128.91,

124.31, 123.62, 121.82, 91.53, 89.87, 82.82, 82.55, 27.95, 15.12.

HRMS calcd for C₁₈H₁₄: 230.1096. Found: 230.1089.

7.32 (d, J ) 7.9 Hz, 1 H), 7.28 (d, J ) 1.1 Hz, 1 H), 7.19 (dd,

J ) 7.9, 1.6 Hz, 1 H), 2.74 (q, J ) 7.5 Hz, 2 H), 1.21 (t, J ) 7.5

Hz, 3 H), 0.23 (s, 9 H), 0.22 (s, 9 H). ¹³C NMR (100 MHz,

CDCl₃) δ 146.57, 132.19, 131.37, 129.07, 123.17, 122.50, 104.97,

103.38, 99.75, 95.60, 27.52, 14.35, -0.056, -0.074. HRMS

calcd for C₁₈H₂₆Si₂: 298.1573. Found: 298.1569.

Tr im er Th ioa ceta te 63. 59 (0.70 g, 2.50 mmol), 3-ethyl-

1-(phenylethynyl)-4-ethynylbenzene (0.61 g, 2.67 mmol), THF

(5 mL), bis(dibenzylideneacetone)palladium(0) (71.80 mg, 0.13

mmol), triphenylphosphine (164 mg, 0.63 mmol), copper(I)

iodide (47.60 mg, 0.25 mmol), N,N-diisopropylethylamine (1.73

mL, 10 mmol) for 5 d afforded 0.67 g (70%) of the title

compound as a yellow solid after gravity liquid chromatogra-

phy (9:1; hexane:ethyl acetate). R_f) 0.49 (9:1; hexane:ethyl

acetate). IR (KBr) 2962, 2930, 2874, 2201, 1691, 1589, 1501,

1459, 1442, 1396, 1356, 1304, 1266, 1118, 1014, 953, 887, 827,

2-Eth yl-1,4-d ieth yn ylben zen e (68). 65 (0.60 g, 2 mmol),

methanol (10 mL), and potassium carbonate (1.66 g, 12 mmol)

afforded 0.27 g (88%) of the title compound as a yellow oil. R_f

) 0.27 (hexane). IR (neat) 3294, 2969, 2935, 2875, 2107, 1603,

1485, 1460, 1243, 896, 832, 735 cm^-1

.

¹H NMR (300 MHz,

CDCl₃) δ 7.39 (d, J ) 7.9 Hz, 1 H), 7.33 (d, J ) 1.1 Hz, 1 H),

7.25 (dd, J ) 7.9, 1.6 Hz, 1 H), 3.31 (s, 1 H), 3.12 (s, 1 H), 2.78

(q, J ) 7.6 Hz, 2 H), 1.23 (t, J ) 7.6 Hz, 3 H). ¹³C NMR (100

MHz, CDCl₃) δ 146.83, 132.74, 131.60, 129.26, 122.53, 121.89,

83.39, 82.29, 81.74, 78.53, 27.33, 14.51.

753, 684, 668, 628 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.53

Dip h en ylth ioester Mon om er 71. 59 (0.70 g, 2.50 mmol),

68 (0.15 g, 1.0 mmol), THF (3 mL), bis(dibenzylideneacetone)-

palladium(0) (72 mg, 0.13 mmol), triphenylphosphine (164 mg,

0.63 mmol), copper(I) iodide (48 mg, 0.25 mmol), N,N-diiso-

propylethylamine (0.70 mL, 4 mmol) for 1 d afforded 0.32 g

(70%) of the title compound as a yellow solid after gravity

liquid chromatography (9:1; hexane:ether). R_f) 0.11 (9:1;

hexane:ether). IR (KBr) 2964, 2928, 2874, 2206, 1912, 1695,

1590, 1500, 1396, 1354, 1118, 1095, 1014, 955, 825, 720, 694,

(d, J ) 8.4 Hz, 2 H), 7.52 (dd, J ) 7.5, 2.2 Hz, 1 H), 7.46 (d, J

) 7.9 Hz, 1 H), 7.42 (d, J ) 2 Hz, 1 H), 7.38 (d, J ) 8.4 Hz, 2

H), 7.36-7.33 (m, 5 H), 2.85 (q, J ) 7.6 Hz, 2 H), 2.43 (s, 3 H),

1.30 (t, J ) 7.5 Hz, 3 H). ¹³C NMR (100 MHz, CDCl₃) δ 193.33,

146.40, 134.33, 132.23, 132.10, 131.70, 131.20, 129.00, 128.48,

128.46, 128.25, 124.61, 123.60, 123.17, 122.07, 93.87, 91.10,

89.70, 89.52, 30.30, 27.71, 14.70. HRMS calcd for C₂₆H₂₀O₂:

380.1235. Found: 380.1224. λ (CH₂Cl₂) ) 230, 234, 328 nm.

Gen er a l P r oced u r es for th e Hyd r olysis of Th ioester s

to Th iols.²⁰(a) A mixture of the thioester, sodium hydroxide

(2 equiv), zinc dust (5 mg), and water (5 mL/mmol of thioester)

were deoxygenated with argon gas for 1 h before THF (5 mL/

mmol of thioester) was added. The reaction was allowed to

stir overnight at room temperature while being purged with

argon gas. 3 M hydrochloric acid was to permit neutralization.

The resulting precipitate was dissolved in degassed chloroform

(5 mL/mmol of thioester) and the organic layer was withdrawn

via syringe and transferred to a Schlenk flask without

exposure to air. Chloroform was added to the aqueous layer

and withdrawn another 3× to permit complete extraction

before the combined organic solvent was removed in vacuo to

afford a solid which was immediately taken into the dry box.

Eluents and other slight modifications are described below for

each material. (b) A mixture of the thioester, 30% ammonium

hydroxide (10 equiv) and THF (2.50 mL/mmol of thioester)

were allowed to stir for 15 min at room temperature while

being purged with argon gas. The reaction mixture was then

617 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.54 (d, J ) 8.1 Hz,

.

4 H), 7.46 (d, J ) 8.1 Hz, 1 H), 7.41 (d, J ) 1.7 Hz, 1 H), 7.39

(d, J ) 8.2 Hz, 2 H), 7.38 (d, J ) 8.3 Hz, 2 H), 7.33 (dd, J )

8.1, 1.7 Hz, 1 H), 2.86 (q, J ) 7.6 Hz, 2 H), 2.43 (s, 3 H), 2.42

(s, 3 H), 1.30 (t, J ) 7.5 Hz, 3 H). ¹³C NMR (100 MHz, CDCl₃)

δ 193.39, 146.41, 134.29, 134.22, 132.18, 132.07, 131.22,

128.98, 124.54, 124.36, 123.11, 122.34, 93.93, 91.05, 90.15,

89.52, 30.29, 27.64, 14.60. HRMS calcd for C₂₈H₂₂O₂S₂:

454.1061. Found: 454.1059. λ (CH₂Cl₂) ) 205, 230, 234, 334

nm.

Dip h en ylth iol Mon om er 74. 71 (0.19 g, 0.40 mmol),

sodium hydroxide (64 mg, 1 mmol), zinc dust (5.0 mg, 0.076

mequiv), water (1 mL), THF (2 mL), and 3 M hydrochloric acid

(0.53 mL) afforded 0.14 g (94%) of the title compound as a

yellow solid with slight impurities. R_f) 0.12 (4:1; hexane:

ether). IR (KBr) 2962, 2927, 2869, 2561, 2204, 1902, 1712,

1656, 1587, 1498, 1461, 1401, 1266, 1099, 1016, 892, 823 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.42 (d, J ) 8.0 Hz, 1 H), 7.37

(d, J ) 8.2 Hz, 4 H), 7.36 (s, 1 H), 7.29 (dd, J ) 8.0, 1.6 Hz, 1

H), 7.23 (d, J ) 8.2 Hz, 2 H), 7.22 (d, J ) 8.4 Hz, 2 H), 3.51 (s,

1 H), 3.50 (s, 1 H), 2.84 (q, J ) 7.5 Hz, 2 H), 1.29 (t, J ) 7.5

Hz, 3 H). ¹³C NMR (125 MHz, CDCl₃) δ 146.56, 132.56, 132.43,

(20) Zervais, L.; Photaki, I.; Ghelis, N. J . Am. Chem. Soc. 1963, 85,

1337.

1408 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

131.44, 129.39, 129.37, 129.25, 123.51, 122.76, 120.88, 120.70,

94.57, 90.78, 90.33, 88.78, 28.02, 14.97. LRMS calcd for

28.02, 15.00, 14.99. LRMS calcd for C₃₄H₂₆S₂: 498. Found:

498. λ (CH₂Cl₂) ) 207, 229, 352 nm.

C

₂₄H₁₈S₂: 370. Found: 370. λ (CH₂Cl₂) ) 229, 234, 340 nm.

Bis(tr im eth ylsilyl) Tetr a m er 67. 32 (0.56 g, 0.78 mmol),

(trimethylsilyl)acetylene (0.12 mL, 0.86 mmol), bis(diben-

zylideneacetone)palladium(0) (22.40 mg, 0.04 mmol), triphen-

ylphosphine (51.10 mg, 0.20 mmol), copper(I) iodide (15 mg,

0.08 mmol), N,N-diisopropylethylamine (0.54 mL, 3.12 mmol),

and THF (5 mL) for 4 d afforded 0.48 g (90%) of the title

compound as a yellow oil after flash liquid chromatography

(9:1; hexane:dichloromethane). R_f) 0.74 (9:1; hexane:dichlo-

romethane). IR (neat) 2963, 2930, 2868, 2152, 1919, 1592,

1501, 1459, 1409, 1248, 1117, 1062, 842, 759, 698, 666, 624

Bis(tr im eth ylsilyl) Dim er 66. 23 (0.91 g, 2.0 mmol),

(trimethylsilyl)acetylene (0.31 mL, 2.20 mmol), bis(diben-

zylideneacetone)palladium(0) (57.40 mg, 0.10 mmol), triphen-

ylphosphine (0.11 g, 0.40 mmol), copper(I) iodide (38.10 mg,

0.20 mmol), N,N-diisopropylethylamine (1.38 mL, 8 mmol), and

THF (4 mL) for 5 d afforded 0.65 g (76%) of the title compound

as a yellow oil after gravity liquid chromatography (hexane).

R_f) 0.21 (hexane). IR (neat) 2964, 2899, 2875, 2154, 1598,

1495, 1458, 1407, 1250, 1222, 857, 760, 701, 636 cm^-1

.

¹H

cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.46 (dd, J ) 7.9, 1.9 Hz,

.

NMR (500 MHz, CDCl₃) δ 7.39 (d, J ) 7.9 Hz, 1 H), 7.38 (d, J

) 7.9 Hz, 1 H), 7.33 (d, J ) 1.2 Hz, 1 H), 7.32 (d, J ) 1.1 Hz,

1 H), 7.25 (dd, 8.0, 1.3 Hz, 2 H), 2.82 (q, J ) 7.6 Hz, 2 H), 2.78

(q, J ) 7.6 Hz, 2 H), 1.27 (t, J ) 7.5 Hz, 3 H), 1.25 (t, J ) 7.5

Hz, 3 H), 0.25 (s, 9 H), 0.24 (s, 9 H). ¹³C NMR (125 MHz,

CDCl₃) δ 147.20, 146.48, 132.77, 132.40, 131.86, 131.27, 129.65,

129.04, 123.80, 123.53, 122.91, 122.82, 105.44, 103.85, 100.27,

96.13, 94.99, 94.99, 89.65, 28.01, 27.97, 14.97, 14.82, 0.37, 0.35.

HRMS calcd for C₂₈H₃₄Si₂: 426.2199. Found: 426.2202.

2 H), 7.42 -7.39 (m, 4 H), 7.35-7.31 (m, 4 H), 7.29-7.26 (m,

2 H), 2.91-2.78 (m, 8 H), 1.33-1.24 (m, 12 H), 0.25 (s, 9 H),

0.24 (s, 9 H). ¹³C NMR (125 MHz, CDCl₃) δ 147.24, 146.71,

146.51, 132.79, 132.58, 132.41, 131.89, 131.36, 131.29, 129.67,

129.23, 129.07, 123.81, 123.76, 123.54, 122.93, 122.83, 105.45,

103.86, 100.34, 96.18, 95.16, 95.11, 95.08, 89.82, 89.77, 89.74,

30.13, 28.08, 28.03, 28.00, 15.05, 14.99, 14.84, 0.38, 0.37.

HRMS calcd for C₄₈H₅₀Si₂: 682.3451. Found: 682.3474.

Dieth yn yl Tetr a m er 70. 67 (0.48 g, 0.70 mmol), methanol

(25 mL), dichloromethane (50 mL), and potassium carbonate

(0.58 g, 4.20 mmol) afforded 0.33 g (88%) of the title compound

as a yellow solid. IR (KBr) 3300, 2964, 2929, 2867, 1593, 1500,

Dieth yn yl Dim er 69. 66 (0.64 g, 1.50 mmol), methanol

(10 mL), dichloromethane (5 mL), and potassium carbonate

(1.24 g, 9.0 mmol) afforded 0.42 g (100%) of the title compound

as a yellow oil. IR (neat) 3297, 3091, 3071, 3036, 2968, 2933,

2874, 1960, 1815, 1727, 1603, 1527, 1479, 1394, 1036, 910, 832,

1459, 1409, 1373, 1116, 1062, 888, 838, 745, 642, 616 cm^-1

.

¹H NMR (300 MHz, CDCl₃) δ 7.49-7.46 (m, 3 H), 7.43 (s, 1

H), 7.40-7.37 (m, 4 H), 7.35-7.28 (m, 4 H), 3.33 (s, 1 H), 3.14

(s, 1 H), 2.90-2.81 (m, 8 H), 1.35-1.24 (m, 12 H). ¹³C NMR

(125 MHz, CDCl₃) δ 147.35, 146.75, 146.73, 146.61, 133.25,

132.58, 132.56, 132.54, 132.45, 132.04, 131.37, 131.32, 129.78,

129.23, 129.10, 123.32, 122.49, 95.12, 94.87, 89.79, 89.76,

89.52, 84.00, 82.62, 82.36, 78.85, 30.10, 28.05, 27.95, 27.83,

15.02, 14.93.

734, 676 cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 7.43 (d, J ) 7.9

.

Hz, 1 H), 7.42 (d, J ) 7.9 Hz, 1 H), 7.360 (d, J ) 1.3 Hz, 1 H),

7.355 (d, J ) 1.1 Hz, 1 H), 7.28 (dd, J ) 7.9, 1.4 Hz, 2 H), 3.33

(s, 1 H), 3.14 (s, 1 H), 2.87-2.79 (two quartets, 4 H), 1.28 (t, J

) 7.6 Hz, 3 H), 1.27 (t, J ) 7.6 Hz, 3 H). ¹³C NMR (125 MHz,

CDCl₃) δ 147.34, 146.63, 133.28, 132.49, 132.05, 131.34, 131.29,

129.82, 129.22, 127.14, 124.12, 123.25, 94.90, 89.54, 84.01,

82.72, 82.37, 78.98, 27.98, 27.86, 15.03, 14.95. HRMS calcd

for C₂₂H₁₈: 282.1408. Found: 282.1407.

Dip h en ylth ioester Tetr a m er 73. 59 (55.60 mg, 0.20

mmol), 70 (35.97 mg, 0.07 mmol), bis(dibenzylideneacetone)-

palladium(0) (5.74 mg, 0.01 mmol), triphenylphosphine (13.11

mg, 0.05 mmol), copper(I) iodide (3.80 mg, 0.02 mmol), N,N-

diisopropylethylamine (0.14 mL, 0.80 mmol), and THF (3 mL)

for 5 d to afforded 17.30 mg (32%) of the title compound as a

yellow waxy solid with slight impurities after flash liquid

chromatography (9:1; hexane:ethyl acetate). R_f) 0.20 (9:1;

hexane:ethyl acetate). Impurities, presumably from disulfide

formation, prevented complete assignment of the aromatic

region. ¹H NMR (400 MHz, CDCl₃) δ 7.56-7.32 (m, 20 H),

3.00-2.80 (four quartets, 8 H), 2.43 (s, 3 H), 2.42 (s, 3 H), 1.40-

1.30 (four triplets, 12 H). LRMS Calcd for C₅₈H₄₆O₂S₂: 838

(100%), 839 (68%), 840 (32%). Found: 838 (100%), 839 (60%),

840 (40%). λ (CH₂Cl₂) ) 197, 209, 218, 228, 359 nm.

Dip h en ylth ioester Dim er 72. 59 (1.04 g, 3.75 mmol), 69

(42 g, 1.50 mmol), THF (10 mL), bis(dibenzylideneacetone)-

palladium(0) (0.11 g, 0.19 mmol), triphenylphosphine (0.25 g,

0.94 mmol), copper(I) iodide (72.40 mg, 0.38 mmol), N,N-

diisopropylethylamine (2.60 mL, 15 mmol) for 5 d to afforded

0.44 g (50%) of the title compound as a yellow waxy solid after

gravity liquid chromatography (9:1; hexane:ethyl acetate). R_f

) 0.26 (9:1; hexane:ethyl acetate). IR (KBr) 2966, 2931, 2871,

2203, 1910, 1701, 1588, 1542, 1500, 1478, 1460, 1435, 1396,

1350, 1264, 1115, 1088, 1014, 947, 888, 826, 616 cm^-1

.

¹H

NMR (400 MHz, CDCl₃) δ 7.54 (d, J ) 8.2 Hz, 2 H), 7.47 (d, J

) 7.9 Hz, 2 H), 7.41 (s, 1 H), 7.39 (d, J ) 8.4 Hz, 2 H), 7.38 (d,

J ) 8.4 Hz, 2 H), 7.35-7.32 (m, 3 H), 7.21 (d, J ) 7.8 Hz, 2

H), 2.89-2.86 (two quartets, 4 H), 2.43 (s, 3 H), 2.42 (s, 3 H),

1.32 (t, J ) 7.6 Hz, 3 H), 1.31 (t, J ) 7.6 Hz, 3 H). ¹³C NMR

(75 MHz, CDCl₃) δ 193.43, 146.49, 146.32, 134.32, 134.26,

134.09, 132.24, 132.20, 132.09, 131.20, 131.04, 129.69, 129.01,

128.87, 128.40, 128.22, 124.58,124.41, 123.54, 122.60, 122.19,

94.77, 93.91, 91.13, 90.13, 89.60, 89.46, 30.33, 27.71, 27.65,

14.68, 14.63. HRMS calcd for C₃₈H₃₀O₂S₂: 582.1687. Found:

582.1684. λ (CH₂Cl₂) ) 229, 234, 272, 350 nm.

Th ioester Sila n e 76. 16 (0.35 g, 0.74 mmol), 60 (0.14 mL,

0.81 mmol), bis(triphenylphosphino)palladium(II) chloride

(0.0052 g, 0.0074 mmol), triphenylphosphine (0.0039 g, 0.015

mmol), copper(I) iodide (0.0029 g, 0.015 mmol), and triethyl-

amine (1 mL) for 2 d afforded 0.34 g (89%) of the title

compound as a brown oil after gravity liquid chromatography

(9:1; hexane:ether). R_f) 0.62 (9:1; hexane:ether). IR (neat)

3054, 2926, 2853, 2209, 2152, 1904, 1715, 1601, 1541, 1497,

1466, 1435, 1397, 1352, 1249, 1224, 1118, 1090, 1016, 949, 842,

Dip h en ylth iol Dim er 75. 72 (0.17 g, 0.30 mmol), sodium

hydroxide (0.10 g, 2.50 mmol), zinc dust (5.0 mg, 0.076

mequiv), water (5 mL), THF (5 mL), and 3 M hydrochloric acid

(0.83 mL) afforded 0.13 g (87%) of the title compound as a

yellow solid with slight impurities. R_f) 0.17 (9:1; hexane:

ethyl acetate). IR (KBr) 2963, 2929, 2868, 2561, 2201, 1899,

1719, 1654, 1589, 1542, 1499, 1459, 1400, 1265, 1181, 1116,

760, 744, 721, 697, 638, 617 cm^-^{1 1}H NMR (400 MHz, CDCl₃)

.

δ 7.52 (d, J ) 8.6 Hz, 2 H), 7.38 (d, J ) 7.9 Hz, 1 H), 7.37 (d,

J ) 8.5 Hz, 2 H), 7.33 (d, J ) 1.3 Hz, 1 H), 7.26 (dd, J ) 8.0,

1.6 Hz, 1 H), 2.74 (t, J ) 7.8 Hz, 2 H), 2.42 (s, 3 H), 1.62 (p, J

) 7.2 Hz, 2 H), 1.32-1.24 (m, 18 H), 0.86 (t, J ) 7.0 Hz, 3 H),

1096, 1013, 954, 890, 823, 744, 700, 620 cm^-1

. Impurities,

0.24 (s, 9 H). HRMS calcd for

Found: 516.2878.

C₃₃H₄₄OSSi: 516.2882.

presumably due from disulfide formation, prevented com-

plete assignment of the aromatic region. ¹H NMR (300 MHz,

CDCl₃) δ 7.46 (d, J ) 8.0 Hz, 1 H), 7.45 (d, J ) 8.0 Hz, 1 H),

7.37 (d, J ) 8.3 Hz, 4 H), 7.32 (d, J ) 7.9 Hz, 1 H), 7.31 (d, J

) 7.9 Hz, 2 H), 7.30 (d, J ) 7.9 Hz, 1 H), 7.25 (d, J ) 8.4 Hz,

2 H), 7.24 (d, J ) 8.5 Hz, 2 H), 3.52 (s, 1 H), 3.51 (s, 1 H),

2.90-2.80 (two quartets, 4 H), 1.31 (t, J ) 7.5 Hz, 3 H), 1.30

(t, J ) 7.5 Hz, 3 H). ¹³C NMR (125 MHz, CDCl₃) δ 146.64,

132.55, 132.54, 132.48, 132.43, 132.40, 131.44, 131.36, 131.27,

129.40, 129.37, 129.25, 129.22, 123.66, 123.62, 122.86, 122.73,

120.89, 120.72, 95.12, 94.61, 90.82, 90.32, 89.78, 88.78, 28.06,

Th ioester Alk yn e 80. 76 (0.32 g, 0.62 mmol), 49%

concentrated hydrofluoric acid (0.021 mL, 1.36 mmol), TBAF

(0.20 mL, 0.68 mmol, 1.0 M in THF) and pyridine (1.24 mL)

at room temperature for 20 min afforded 0.22 g (81%) of the

title compound as a brown oil after gravity liquid chromatog-

raphy (9:1; hexane:ether). R_f) 0.55 (9:1; hexane:ether) IR

(neat) 3298, 2924, 2853, 2101, 1712, 1601, 1494, 1461, 1120,

1016, 949, 828 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.53 (d, J

.

) 8.5 Hz, 2 H), 7.42 (d, J ) 7.9 Hz, 1 H), 7.37 (d, J ) 8.6 Hz,

2 H), 7.35 (d, J ) 1.3 Hz, 1 H), 6.38 (dd, J ) 7.9, 1.6 Hz, 1 H),

Rapid Syntheses of Oligo(1,4-phenylene ethynylene)s

J . Org. Chem., Vol. 62, No. 5, 1997 1409

3.31 (s, 1 H), 2.75 (t, J ) 7.8 Hz, 2 H), 2.42 (s, 3 H), 1.63 (p, J

) 7.2 Hz, 2 H), 1.32-1.24 (m, 18 H), 0.86 (t, J ) 7.1 Hz, 3 H).

Bisth ioester 83. 59 (0.26 g, 0.92 mmol), 80 (0.21 g, 0.46

mmol), triethylamine (1 mL), bis(triphenylphosphino)palla-

dium(II) chloride (0.0065 g, 0.0092 mmol), triphenylphosphine

(0.0047 g, 0.018 mmol), and copper(I) iodide (0.0034 g, 0.018

mmol) for 1 d afforded 0.16 g (59%) of the title compound as a

yellow solid after gravity liquid chromatography (9:1; hexane:

ether). R_f) 0.20 (9:1; hexane:ether). IR (KBr) 3032, 2924,

2855, 2677, 2254, 2211, 1907, 1705, 1594, 1541, 1498, 1461,

1400, 1354, 1305, 1267, 1116, 1012, 950, 908, 829, 731, 615

131.90, 131.84, 129.36, 129.16, 128.95, 128.85, 128.80, 128.70,

128.67, 128.60, 128.31, 124.83, 123.63, 123.37, 123.24, 123.16,

123.04, 104.01, 100.11, 95.07, 91.52, 90.46, 90.05, 39.80, 29.42,

39.26, 37.50, 37.04, 36.90, 36.18, 36.14, 35.48, 35.09, 34.75,

34.70, 33.20, 32.81, 32.50, 32.36, 32.22, 32.00, 31.72, 31.30,

31.07, 31.03, 30.98, 30.81, 30.67, 30.14, 30.13, 30.10, 30.05,

30.01, 30.00, 29.93, 29.90, 29.80, 29.78, 29.72, 29.68, 29.54,

29.47, 29.34, 28.88, 28.60, 28.39, 28.30, 27.82, 27.72, 27.51,

25.69, 23.24, 23.11, 23.07, 22.97, 21.11, 20.55, 20.10, 19.64,

14.81, 14.53, 14.39, 11.82, 4.96, 0.37.

Th ioester Sila n e 79. 46 (0.49 g, 0.11 mmol), 60 (0.039 mL,

0.22 mmol), bis(dibenzylideneacetone)palladium(0) (0.0032 g,

0.0055 mmol), triphenylphosphine (0.0073 g, 0.028 mmol),

copper(I) iodide (0.0010 g, 0.0055 mmol), N,N-diisopropyleth-

ylamine (2 mL), and THF (4 mL) for 3 days afforded 0.33 g

(66%) of the title compound as a waxy yellow solid after gravity

liquid chromatography (2:1; hexane:chloroform). R_f) 0.53 (2:

1; hexane:chloroform). IR (KBr) 2924, 2855, 2203, 2151, 1710,

cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.54 (d, J ) 8.3 Hz, 2 H),

.

7.53 (d, J ) 8.2 Hz, 2 H), 7.46 (d, J ) 7.9 Hz, 1 H), 7.41-7.38

(m, 5 H), 7.33 (dd, J ) 8.0, 2.5 Hz, 1 H), 2.83 (t, J ) 7.6 Hz, 2

H), 2.42 (s, 3 H), 2.41 (s, 3 H), 1.69 (p, J ) 7.5 Hz, 2 H), 1.38-

1..25 (m, 18 H), 0.89 (t, J ) 7.0 Hz, 3 H). ¹³C NMR (100 MHz,

CDCl₃) δ 193.27 (2C), 145.28, 134.29, 134.23, 132.24, 132.19,

132.05, 131.98, 129.00, 128.29, 128.24, 124.56, 124.36, 122.98,

122.56, 93.85, 91.13, 90.21, 89.79, 34.64, 31.98, 30.64, 30.29,

29.75, 29.75, 29.72, 29.69, 29.63, 29.61, 29.43, 22.76, 14.21.

HRMS calcd for C₃₈H₄₂O₂S₂: 594.2626. Found: 594.2618.

Th ioester Sila n e 77. 34 (0.38 g, 0.29 mmol), 60 (0.13 mL,

0.75 mmol), bis(dibenzylideneacetone)palladium(0) (0.0086 g,

0.015 mmol), triphenylphosphine (0.020 g, 0.073 mmol), cop-

per(I) iodide (0.0055 g, 0.029 mmol), N,N-diisopropylethyl-

amine (0.40 mL, 2.32 mmol), and THF (4 mL) for 3 d afforded

0.28 g (73%) of the title compound as a waxy yellow solid after

gravity liquid chromatography (9:1; hexane:ether). R_f) 0.61

(9:1; hexane:ether). IR (KBr) 2924, 2853, 2206, 2150, 1710,

1594, 1502, 1460, 1386, 1261, 1094, 1027, 806 cm^-^{1 1}H NMR

.

(400 MHz, CDCl₃) δ 7.54 (d, J ) 8.0 Hz, 2 H), 7.50-7.46 (m,

14 H), 7.38-7.31 (m, 36 H), 2.90-2.80 (m, 32 H), 2.42 (s, 3

H), 1.80-1.70 (m, 32 H), 1.40-1.20 (m, 288 H), 0.90-0.80 (m,

48 H), 0.25 (s, 9 H). ¹³C NMR (125 MHz, CDCl₃) δ 193.68,

145.62, 145.56, 145,32, 143.57, 143.55, 140.46, 134.61, 133.42,

132.88, 132.58, 132.48, 132.37, 132,34, 132.32, 132.15, 132.06,

131.92, 131.86, 129.80, 129.60, 129.39, 129.35, 129.28, 129.19,

129.00, 128.986, 128.86, 128.81, 128.76, 128.71, 128.68, 128.63,

128.33, 125.13, 124.84, 124.11, 123.82, 123.64, 123.51, 123.40,

123.26, 123.20, 123.08, 122.68, 95.41, 95.14, 91.88, 91.57,

91.45, 90.50, 90.41, 90.08, 89.42, 89.36, 88.66, 88.55, 78.78,

39.83, 39.52, 39.44, 39.29, 37.53, 37.08, 36.93, 36.21, 36.17,

35.52, 35.13, 35.08, 34.83, 34.78, 34.72, 33.23, 33.04, 33.00,

32.84, 32.53, 32.40, 32.26, 31.78, 31.75, 31.44, 31.36, 31.10,

31.06, 30.84, 30.66, 30.19, 30.14, 30.10, 30.06, 30.03, 29.93,

29.85, 29.76, 29.72, 28.91, 28.77, 28.62, 28.41, 28.32, 27.87,

27.76, 27.56, 27.45, 27.15, 23.50, 23.27, 23.24, 23.15, 23.11,

23.01, 20.59, 20.13, 19.70, 19.66, 14.84, 14.70, 14.57, 14.43,

11.85, 4.97, 0.40. Anal. Calcd for C₃₃₃H₄₆₄OSSi: C, 88.03; H,

10.30. Found: C, 86.71; H, 10.80.²¹

1594, 1500, 1460, 1403, 1250, 1118, 950, 835, 758, 617 cm^-1

.

¹H NMR (400 MHz, CDCl₃) δ 7.54 (d, J ) 8.4 Hz, 2 H), 7.46

(d, J ) 7.9 Hz, 2 H), 7.45 (d, J ) 7.9 Hz, 2 H), 7.39 (d, J ) 8.2

Hz, 2 H), 7.38 (d, J ) 8.3 Hz, 2 H), 7.37-7.26 (m, 6 H), 2.83 (t,

J ) 7.4 Hz, 6 H), 2.75 (t, J ) 6.3 Hz, 2 H), 2.42 (s, 3 H), 1.70-

1.20 (m, 8 H), 1.41-1.22 (m, 72 H), 0.86-0.83 (m, 12 H), 0.25

(s, 9 H). ¹³C NMR (125 MHz, CDCl₃) δ 193.37, 146.11, 145.60,

134.73, 134.70, 134.44, 132.92, 132.88, 132.65, 132.57, 132.48,

132.43, 132.27, 132.22, 132.00, 131.90, 129.60, 129.38, 129.22,

129.07, 128.86, 128.70, 128.65, 124.85, 123.80, 123.73, 123.71,

123.30, 123.25, 123.08, 104.14, 100.08, 95.25, 95.21, 95.12,

91.65, 91.40, 90.57, 90.12, 90.08, 35.51, 35.18, 34.83, 34.63,

34.45, 31.27, 31.15, 31.06, 30.96, 30.87, 30.70, 30.63, 30.58,

30.25, 30.21, 30.08, 29.92, 29.34, 28.54, 28.38, 23.33, 23.21,

Th ioester Alk yn e 82. 79 (0.27 g, 0.060 mmol), 49% HF

(0.40 mL, 25.95 mmol), TBAF (3.84 mL, 13.26 mmol, 1.0 M in

THF), pyridine (2 mL), and THF (15 mL) overnight afforded

0.14 g (52%) of the title compound as a waxy yellow solid after

flash liquid chromatography (2:1; hexane:chloroform). R_f)

0.50 (2:1; hexane:chloroform). IR (KBr) 3302, 2926, 2856,

2204, 2096, 1714, 1655, 1590, 1504, 1466, 1386, 1262, 1116,

23.10, 14.74, 14.66, 14.60, 14.52. LRMS calcd for C₉₃H₁₂₈

-

OSSi: 1321 (88%), 1322 (100%), 1323 (63%). Found: 1321

(95%), 1322 (100%), 1323 (70%).

1030, 960, 896, 836, 798, 724 cm^-^{1 1}H NMR (400 MHz, CDCl₃)

.

Th ioester Alk yn e 81. 77 (0.15 g, 0.11 mmol), 49%

concentrated hydrofluoric acid (0.0074 mL, 0.48 mmol), TBAF

(0.070 mL, 0.24 mmol, 1.0 M in THF), and pyridine (1.24 mL)

at room temperature for 30 min afforded 0.12 g (87%) of the

title compound as a waxy yellow solid after flash liquid

chromatography (9:1; hexane:ether). R_f) 0.57 (9:1; hexane:

ether) IR (KBr) 3302, 2926, 2856, 2206, 2101, 1906, 1713, 1597,

δ 7.54 (d, J ) 8.0 Hz, 2 H), 7.49-7.46 (m, 14 H), 7.38-7.31

(m, 36 H), 3.36 (s, 1 H), 2.90-2.80 (m, 32 H), 2.42 (s, 3 H),

1.80-1.70 (m, 32 H), 1.40-1.20 (m, 288 H), 0.90-0.80 (m, 48

H).

Bisth ioester 84. 59 (0.011g, 0.039 mmol), 82 (0,12 g, 0.026

mmol), bis(dibenzylideneacetone)palladium(0) (0.0012 g, 0.0020

mmol), triphenylphosphine (0.0026 g, 0.0098 mmol), copper-

(I) iodide (0.00038 g, 0.0020 mmol), N,N-diisopropylethylamine

(2 mL, 11.48 mmol), and THF (3 mL) for 3 days afforded 0.070

g (58%) of the title compound as a waxy yellow solid after

gravity liquid chromatography (3:1; hexane:chloroform). R_f)

0.43 (3:1; hexane:chloroform). IR (KBr) 2923, 2853, 2204,

1716, 1662, 1556, 1502, 1464, 1388, 1314, 1260, 1120, 1018,

1498, 1459, 1116, 827, 616 cm^-^{1 1}H NMR (400 MHz, CDCl₃)

.

δ 7.54 (d, J ) 8.4 Hz, 2 H), 7.46 (d, J ) 7.8 Hz, 2 H), 7.43 (d,

J ) 7.9 Hz, 2 H), 7.38 (d, J ) 8.5 Hz, 2 H), 7.37-7.27 (m, 8

H), 3.32 (s, 1 H), 2.83 (t, J ) 7.4 Hz, 6 H), 2.77 (t, J ) 7.3 Hz,

2 H), 2.43 (s, 3 H), 1.70-1.60 (m, 8 H), 1.34-1.22 (m, 72 H),

0.86-0.83 (m, 12 H). LRMS calcd for C₉₀H₁₂₀OS: 1249 (98%),

1250 (100%), 1251 (55%). Found: 1249 (96%), 1250 (100%),

1251 (63%).

890, 826, 692 cm^-^{1 1}H NMR (400 MHz, CDCl₃) δ 7.54 (d, J )

.

Th ioester Sila n e 78. 42 (0.13 g, 0.055 mmol), 60 (0.020

g, 0.75 mmol), bis(dibenzylideneacetone)palladium(0) (0.0016

g, 0.0028 mmol), triphenylphosphine (0.0037 g, 0.014 mmol),

copper(I) iodide (0.00053 g, 0.0028 mmol), N,N-diisopropyl-

ethylamine (2 mL), and THF (3 mL) for 3 days afforded 0.077

g (59%) of the title compound as a waxy yellow solid after

gravity liquid chromatography (2:1; hexane:chloroform). R_f)

0.56 (2:1; hexane:chloroform). IR (KBr) 2928, 2858, 2198,

8.4 Hz, 2 H), 7.48-7.46 (m, 14 H), 7.40-7.32 (m, 40 H), 2.90-

2.80 (m, 32 H), 2.43 (s, 3 H), 2.41 (s, 3 H), 1.75-1.65 (m, 32

H), 1.4-1.20 (m, 288 H), 0.90-0.80 (m, 48 H). ¹³C NMR (75

MHz, CDCl₃) δ 193.80, 145.62, 138.76, 136.34, 135.42, 134.61,

132.80, 132.56, 132.54, 132.46, 132.36, 132.32, 132.14, 131.89,

131.16, 129.34, 129.14, 128.94, 128.84, 128.80, 128.69, 128.59,

124.82, 124.06, 123.61, 123.46, 123.23, 123.14, 123.04, 95.06,

91.51, 90.44, 90.02, 36.17, 35.07, 34.72, 32.33, 31.74, 31.05,

31.01, 30.79, 30.67, 30.59, 30.12, 30.11, 30.08, 30.03, 29.99,

2154, 1716, 1510, 1468, 1398, 1262, 1126, 960, 840, 732 cm^-1

.

¹H NMR (400 MHz, CDCl₃) δ 7.54 (d, J ) 8.4 Hz, 2 H), 7.48-

7.46 (m, 8 H), 7.40-7.32 (m, 18 H), 2.85-2.75 (m, 16 H), 2.42

(s, 3 H), 1.75-1.65 (m, 16 H), 1.40-1.20 (m, 144 H), 0.90-

0.80 (m, 24 H), 0.25 (s, 9 H). ¹³C NMR (125 MHz, CDCl₃) δ

193.77, 146.11, 145.62, 145.32, 143.56, 134.62, 134.60, 133.37,

132.76, 132.57, 132.47, 132.36, 132.34, 132.32, 132.14, 132.02,

(21) Incomplete carbon combustion in high MW materials with high

unsaturated carbon content is a commonly observed property. See

reference 8 and (a) Wallow, T. I.; Novak, B. M. J . Am. Chem. Soc. 1991,

113, 7411. (b) Stephens, E. B.; Tour, J . M. Macromolecules 1993, 26,

2420.

1410 J . Org. Chem., Vol. 62, No. 5, 1997

J ones et al.

29.97, 29.88, 29.78, 28.36, 28.11, 27.80, 27.70, 23.24, 23.09,

20.09, 14.51. Anal. Calcd for C₃₃₈H₄₆₂O₂S₂: C, 87.84; H, 10.08.

Found: C, 83.52; H, 9.70.²¹

Molecular Design Ltd. for the use of their synthetic data

base. We thank Timothy P. Burgin for help in deriving

the polymer-support equations.

Ack n ow led gm en t. Initial phases of this work were

supported by the Office of Naval Research and the

National Science Foundation (EHR-91-08772, DMR-

9158315). The present work is supported by the De-

fense Advanced Research Projects Agency. We thank

Farchan Laboratories for a gift of (trimethylsilyl)-

acetylene, FMC for a gift of alkyllithium reagents, and

Su p p or tin g In for m a tion Ava ila ble: ¹H NMR spectra for

compounds 1-34, 36, 37, 39-49, 58, and 61-84 (101 pages).

This material is contained in libraries on microfiche, im-

mediately follows this article in the microfilm version of the

journal, and can be ordered from the ACS; see any current

masthead page for ordering information.

J O962336Q

Article Doi

Rapid Solution and Solid Phase Syntheses of Oligo(1,4-phenylene ethynylene)s with Thioester Termini: Molecular Scale Wires with Alligator Clips. Derivation of Iterative Reaction Efficiencies on a Polymer Support

DOI: 10.1021/jo962336q

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