Synthesis, X-ray structure analysis and topochemical photopolymerization of 2,5-dimethoxyphenyl- and quinone-substituted octa-3,5-diynes

TETRAHEDRON

Pergamon

Tetrahedron 56 (2000) 6781±6794

Synthesis, X-Ray Structure Analysis and Topochemical

Photopolymerization of 2,5-Dimethoxyphenyl- and

Quinone-substituted Octa-3,5-diynes

*

Hermann Irngartinger and Markus Skipinski

È

Organisch-Chemisches Institut der Universitat Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany

Received 10 October 1999; accepted 7 March 2000

AbstractÐThe octa-3,5-diynes 3a±g have been synthesized. Subsequent oxidation of 3a±g gave the 1,8-quinone-substituted octa-3,5-

diynes 4a±g. The molecular structures of the diynes a-3b, b-3b, 3c, 3e, 3f and 4f have been determined by X-ray diffraction. UV-irradiation

of diyne 3c afforded in a single crystal-to-single crystal transformation the highly-ordered polymer 5 under topochemical control. The

transformation of 3c into polymer 5 was observed by X-ray diffraction analysis. Irradiation of 4d yielded the ®rst quinone-substituted

Introduction

unit between the 2,5-dimethoxyphenyl- and the diyne

substituent,⁹which is mainly caused by extension of conju-

gation, the spacer was expanded by one methylene unit. By

introduction of the ethylene-spacer and application of the

following synthetic route (Scheme 1) we were able to

synthesize the ®rst quinone-substituted diynes starting

from the corresponding 2,5-dimethoxybenzyl halogenides

1a±g in three steps.

In 1969, Wegner ®rst characterized the solid-state polymer-

ization of conjugated diynes.¹The polymerization,

accomplished by heat, irradiation or pressure, was found

to lead to highly ordered polymers.^2,3

The synthesis of organic metals involves the assembly of a

molecular solid of crystalline structure, which favors the

metallic state.⁴This implies chain-like structures in which

donors and acceptors stack in parallel chains, and a uniform

structure where each molecule should be equidistant from

its neighbor. Such structures are common in the tetracyano-

benzoquinodimethane (TCNQ) salts^5,6or dicyanobenzo-

quinodiimine (DCNQI) CT complexes.⁷

The Grignard-coupling of the 2,5-dimethoxybenzyl halo-

genides 1a±g with prop-2-ynyl magnesium bromide¹⁰

leads to the temperature sensitive, colorless, liquid

respectively low-melting 4-(2,5-dimethoxyphenyl)but-1-

ynes 2a±g, which were obtained free of allene-isomers.

Copper(I)-catalyzed coupling of the resulting 3-(2,5-

dimethoxyphenyl)but-1-ynes 2a±g under Hay conditions

with CuCl´tmeda in DME in a strong oxygen stream gave

the octa-3,5-diynes 3a±g in yields of 34±85% from which

3c is light sensitive.

By combining the favorable aspects of the highly ordered

diyne polymers and the geometric dependency of conduc-

tivity of organic metals in the case of quinoid compounds,

we sought a convenient method for the synthesis of quinone-

substituted diynes as precursors for a wide range of dicyano-

benzoquinodiimine dialkyne derivatives. In addition the

competitive photo- and thermochemical behavior of the

topochemical ambident quinone-substituted diynes were

of special interest.⁸

The but-1-ynes 2a±g and octa-3,5-diynes 3a±g were fully

1

characterized by their H NMR-, ¹³C NMR-, IR-spectro-

scopical and mass spectrometrical data. The crystal struc-

ture of octa-3,5-diyne 3b, 3c, 3e and 3f was investigated by

X-ray diffraction analysis (Table 3)¹¹and showed that 3b

crystallizes in an a- and a b-modi®cation (Figs. 1 and 2).

Bond lengths and angles of the octa-3,5-diynes a-3b, b-3b,

3c, 3e and 3f in crystal¹¹are in the usual range.¹²The pack-

ing parameters (Table 1) obtained from the crystal structures

of diyne a-3b, b-3b, 3c, 3e and 3f are in accord with the

observed solid-state reactivities. The signi®cance of the

intermolecular distances and angles given in Table 1 can

be seen in Schemes 2 and 3.

Results and Discussion

To prevent the observed oxidation of the methylene-spacer

Keywords: diynes; quinones; polymers; photochemistry in solid-state.

* Corresponding author. Tel.: 149-6221-54-8422; fax: 149-6221-54-

4205; e-mail: e56@ix.urz.uni-heidelberg.de

PII: S0040-4020(00)00500-7

6782

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

Scheme 1. Synthesis of 4a±g; reagents and conditions: (a) C₃H₃MgBr, diethyl ether, rt, 1 day; (b) CuCl´tmeda, DME, 35±368C, 1±2 days; (c) CAN, CH₃CN,

H₂O, 25±308C, 45 min.

Figure 1. Molecular structure of a-3b in the solid state; H atoms are not numbered for clarity.

Figure 2. Molecular structure of b-3b in the solid state; H atoms are not numbered for clarity.

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6783

Table 1. Stacking parameters of a-3b, b-3b, 3c, 3e and 3f. For de®nition of

D, d and g see Schemes 2 and 3, for Dg and s see text

The correlation between d and distance s usually found in

the literature¹⁶is given by the formula sd sin (g). The

deviation from g is Dg, which is calculated from the

formula Dgug245u. For signi®cant reactivity of slipped

Ê

D [A]

Ê

D [A]

Ê

s [A]

g [8]

Dg [8]

Ê

a-3b

4.155(4) 6.076(4) 53.2(3)

8.2(3)

4.865(4)

diyne stacks, the upper limit for D is 4.3 A and for d is

31.0(3) 12.0(3) 3.129(4)

3.574(3) 5.023(1) 45.4(2) 0.4(2) 3.577(2)

4.248(3) 4.498(1) 60.4(2) 15.4(2) 3.911(4)

Ê

5.2 A, g should be close to 458, and s should be in the

3c

3e

13±16

Ê

range 3.4±4.0 A.

Tolerance range^a

3.4±4.3

4.7±5.2

45^10

0±10

3.4±4.0

b-3b

3f

3.746(2) 3.729(2) 74.5(2)

3.716(3) 3.707(3) 71.4(2)

±

In the case of vertical packing arrangement of the monomers

another kind of topochemical 1,4-polyaddition of diynes

may be observed which leads to the formation of all-Z-

poly(but-1-en-3-ynylene)s (Scheme 3).

Tolerance range^b

3.4±4.3

90^10

^aFormation of all-E-poly(but-1-en-3-ynylene).

^bFormation of all-Z-poly(but-1-en-3-ynylene).

Interestingly, there is no certain example of an all-Z-poly-

mer reported in the literature with diyne monomers stacked

as steps of a ladder. A crystal of hexa-2,4-diynedioic acid

dihydrate became violet then black in the course of the

X-ray diffraction analysis, suggesting that the compound

polymerize during X-ray diffraction.¹⁷For vertical diyne

Ê

stacks D and d should be in the range 3.4±4.3 A and g

should be close to 908.¹⁶

The structure determination of a single crystal of 3c (Fig. 3)

crystallized from n-hexane/benzene (10:1) in space group

P2₁/c (Table 3). The monoclinic cell unit exhibits cell

Ê

constants of a5.023(1) A, b35.63(1) A, c6.655(2) A

and a b-angle of 92.45(2)8. The corresponding cell volume

is V1190.2(6) A with Z2 and a calculated density of

Ê ³

D_calc1.21£10³kg m²³

.

Scheme 2. 1,4-Polyaddition of conjugated diynes to all-E-poly(but-1-en-3-

ynylene)s.

The centrosymmetrical molecular units of 3c are arranged in

stacks along the crystallographic axis a and c. While

stacking arrangement in the c direction exhibits no topo-

chemical relevant contacts, along axis a a short contact of

Ê

D3.574(3) A is observed (Fig. 4). The stacking distance of

Ê

the molecular units of 3c amounts to d5.023(1) A. The

angle between the diyne-rods and the stacking axis a is

Ê

g45.4(2)8. With Dg0.4(2)8 and s3.577(2) A the

diyne units are ideally arranged for a topochemical 1,4-

polyaddition. The observed light-sensitivity of 3c is hereby

explained and is discussed in the following paragraph.

In irradiation experiments and under thermal annealing of

the investigated diynes 3a±g solely 3c showed a detectable

topochemical reactivity. Octa-3,5-diyne 3c either photo-

chemically or thermally forms the bronze-orange colored

polymer 5. The crystalline structure of poly(but-1-en-3-

ynylene) 5 was proven by the partial single crystal-to-single

Scheme 3. 1,4-Polyaddition of conjugated diynes to all-Z-poly(but-1-en-3-

ynylene)s.

Figure 3. Molecular structure of 3c in crystal. H atoms are not numbered for clarity.

6784

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

I

II

Figure 4. Stacking arrangement of 3c in the crystal along axis a with the short distances of D3.574(3) A between alkyne C atoms C13 , C13 , C13^IIIand

Ê

C13^IVof neighboring molecules. Symmetry operations: (2x12, 2y11, 2z12); (x11, y, z); (2x13, 2y11, 2z12); (x12, y, z).

Figure 5. Single crystal-to-single crystal transformation of octa-3,5-diyne 3c to the crystalline poly(but-1-en-3-ynylene) 5.

crystal transformation of 3c to 5 (Fig. 5) detected by X-ray

diffraction.

k_monomer0.82 and k_polymer0.18 obtained from re®nement

of the irradiated crystal the crystallographically determined

yield of the single-crystalline poly(but-1-en-3-ynylene) 5

was 18%. Work-up of the irradiated monomer crystal of

3c by THF extraction for 3 h to remove unreacted monomer

gave 37% yield of poly(but-1-en-3-ynylene) 5. The

irradiated single crystal was found to crystallize in the

space group P2₁/c (Table 4). The cell constants at 193 K

For identi®cation of the structure of polymer 5 ®rst the

structure of monomer 3c was determined by X-ray

diffraction analysis. Then the same monomer single crystal

was irradiated with light (l$450 nm) for 6 h at 158C and

measured by X-ray diffraction analysis a second time. The

re®nement was started with the previous obtained data of

the monomer and the resulting difference electron

density was assigned to the structure of the polymer.

On the basis of the resulting occupation numbers of

Ê

are a4.940(1) A, b35.67(5) A and c6.733(4) A with a

Ê ³

b-angle of 92.53(3)8. The cell volume is V1185(2) A

with Z2 and the calculated density is D_calc

1.22£10³kg m²³. Because of the conventional R-value of

Figure 6. Molecular structure of 3e in the crystal. H atoms are not numbered for clarity.

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6785

0

Figure 7. Packing arrangement of 3e in the crystal along the bc-diagonal plane with distances of C4⁰´´´F⁰⁰⁰4.048 A (broken-lined, outlined) and C4 ´´´F

Ê

3.988(2) A (broken-lined, ®lled) of neighboring molecules. H atoms are omitted for clarity. Symmetry operations: (x11, y, z); (2x, 2y11, 2z11); (2x11,

2y11, 2z11).

1

21,22

Ê ³

Table 2. Correlation of the volume increment DV [A ] of the substituents R and R²

with the conformation of the ethylene spacers u(CH₂±CH₂)

[scsynclinal; apantiperiplanar] of a-3b, b-3b, 3c, 3e and 3f in the solid state

3e: R¹F; R²H

a-3b: R¹CH₃; R²H

b-3b: R¹CH₃; R²H

3f: R¹Cl; R²H

3c: R¹CH₃; R²CH₃

u(CH₂±CH₂)

DV(R 1R ) [A ]

sc, sc

11.6

sc, sc

25.5

sc, ap

25.5

sc, ap

21.9

ap, ap

47.0

1

2

Ê ³

00

Ê

0.137, a discussion of the bonding geometry of 5 is not

meaningful.

C4´´´F 3.988(2) A a strong in¯uence on the arrangement

of the molecules in the crystal (Fig. 7). The antiparallel

oriented C4±F and C4⁰⁰±F⁰⁰dipoles seem to determine the

crystal packing arrangement. The CF dipoles in octa-3,5-

diyne 3e are oriented stair-like head-to-tail. The resulting

attractive dipole±dipole interactions create crystal packing

forces which cause an S-like deformation of the C10±C11±

C12±C12⁰±C11⁰±C10⁰-hexa-2,4-diyne-1,6-ylene-group

with angles of C10±C11±C12 173.5(2)8 and C11±C12±

C12⁰178.4(2)8 and lead to a high crystal packing density,

which is re¯ected by the calculated density of

Compared to monomer 3c, the irradiated crystal showed a

Ê

reduction of axis a by 0.083(1) A and an elongation of axis c

Ê

by 0.078(4) A. The length of axis b and the value of the

b-angle remained the same. Before and after irradiation

the determined cell volumes stay within the same scope of

calculated deviation. By the `principle of least motion'^18±20

the crystal systems of 3c and 5 exhibit a very similar

arrangement of atoms. In the irradiated crystal of 5 the

2-(2,5-dimethoxy-3,4-dimethylphenyl)ethyl-substituents in

the monomeric and polymeric part of the crystal nearly

have identical positions. The atoms of the diyne unit,

however, changed their positions in the course of bond

formation to the polymeric backbone in the ratio described

above.

D_calc1.4£10³kg m²³

.

The structure of the octa-3,5-diynes a-3b, b-3b, 3c, 3e and

3f differ by the conformations of their ethylene-bridges. By

correlating the volume increment of the substituents R¹and

R

octa-3,5-diynes a-3b, b-3b, 3c, 3e and 3f in the solid state

(Table 2) the following tendency is observed.

^{2 21,22}with the conformation of the ethylene spacer of the

The crystal structure of 3e (Fig. 6) was determined by X-ray

analysis of a single crystal of 3e obtained from a solution of

Å

[D₆]-benzene. The space group is P1 with Z1 (Table 3).

With increasing space requirement of substituents R¹and

R²and independent of their inductive effects, the con-

formation of the ethylene spacer alters from synclinal to

antiperiplanar.

The dipole character of the C4±F bond of 3e exerts by

intermolecular contacts of C4´´´F⁰4.048(2) A and

Ê

Scheme 4. Topochemical polymerization of 4d to poly(but-1-en-3-ynylene) 6.

6786

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

Figure 8. Absorption wavelength l of poly(but-1-en-3-ynylene)s compared by their conjugation length k. The calculated maximum absorption wavelength

_maxis about 622 nm.²⁴

l

The CAN-oxidation of the octa-3,5-diynes 3a±g in aqueous

acetonitrile at 25±308C gave the yellow to yellow-orange

colored crystalline quinone-substituted octa-3,5-diynes

4a±g which was found to be light sensitive in the

case of 4d.

approximately a minimum chain length of the polymer

chain (Fig. 8) disregarding color shifts due to torsion of

the backbone or electronic effects.²⁴

Corresponding to Fig. 8 the polymerization degree of 6 can

be estimated to n.70 due to the intensive blue color of the

polymer. The observed color-change from blue to red after

the work-up is not unusual for poly(but-1-en-3-

ynylene)s.^24,25The chromophore backbone reacts sensitive

to conformational changes with an absorption ®eld shift.^26,27

In the case of 6, destruction of the host lattice, by addition of

solvent in the work-up process, leaded to a sterical relaxa-

tion of the bulky-substituted polymer under twisting of the

polymer backbone. In consequence, the absorption maxi-

mum is shifted to a lower wavelength and the worked-up

polymer 6 has a red color.

In daylight, 4d turned blue after few minutes and became

deep blue within 2 h. Irradiation of 4d with UV light

(l$254 nm) produced similar colors within 15 min. The

aforementioned color is those of the irradiation product

prior to work-up. After 3 h of irradiation, work-up of the

blue polymer by ethyl acetate extraction yielded 30% of 6

(Scheme 4) as a red, insoluble solid.

Because of the known insolubility of poly(but-1-en-3-

ynylene), only oligomers of up to n4 were observed by

®eld desorption-mass spectrometry (FD-MS), with correct

isotopic peak distribution for [4d]¹_n(n1±2). The IR-spec-

trum of 6 showed peaks at 2161 cm²¹(w, CuC),

1643 cm²¹(vs, CvO) and 1625 cm²¹(w, CvC). Solid

state-Raman experiments resulted in a strong signal at n~

2087 cm²¹for the CuC-group and gave a band of medium

intensity at 1466 cm²¹for the CvC-bond.

The quinone-substituted octa-3,5-diyne 4f (Fig. 9) crystal-

lized from benzene in space group C2/c with Z4 as a 1:1-

benzene adduct in orange colored plates. The molecular

structure of 4f shows an inversion center. Within the

scope of deviation the observed bond lengths¹¹are com-

parable to bond lengths reported in the literature.¹²With

bond angles of C3±C4±Cl1 123.3(5)8, C5±C4±Cl1

114.4(4)8 and C2±C1±C7 116.7(5)8, C6±C1±C7

122.7(5)8, respectively, a signi®cant shift is observed for

the atoms Cl1 and C7 in direction to adjacent carbonyl

groups.^28±31By this, all substituents of the cyclohexa-1,4-

dienyl units are arranged like paddles of a millwheel. The

hexa-2,4-diynylene unit shows an S-like deformation with

bond angles of C8±C9±C10 173.0(7)8 and C9±C10±C10⁰

An important criterion to determine the chain length of the

often insoluble poly(but-1-en-3-ynylene) polymers is their

color. In 1976 R. H. Baughman and R. R. Chance formu-

lated for poly(but-1-en-3-ynylene)s a correlation between

p±p^p-transition energy and the conjugation length,²³

which is represented by Eq. (1).

ꢀ

ꢁ

h²

1

p

E_p!p

1 0:83V₀1 2

ꢀ1

8m_eL²ꢀ4k 1 1

4k

where h6.62618£10²³⁴J s; c2.997925£10⁸m s²¹; m_e

9.10953£10²³¹kg;

L1.36 A 1.36£10²¹⁰m;

V₀

Ê ²³

2.4 eV²³3.84526£10²¹⁹J; knumber of butenyne units;

the corresponding maximum absorption wavelength is

calculated to

l_max lim lꢀk 622:42 nm

ꢀ2

k!1

If an optimal conjugation of the butenyne units is realized

the polymer maximally absorbs in the orange±red spectral

®eld and appears blue. In the reverse case, it is possible from

the color of the polymer and the corresponding absorption

wavelength to deduce a conjugation length and thereby

Figure 9. Molecular structure of 4f in the solid state; H atoms are not

numbered for clarity.

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6787

Figure 10. Part of the stacking structure of 4f in the crystal along the diagonal plane a,b with intermolecular distances between the carbonyl unit and the vinyl

0

Ê

double bond of O1´´´C4 [3.328(8) A] and C2´´´C3 [3.414(8) A]. Symmetry operation: (2x, 2y13, 2z).

Ê

0

Ê

178.5(7)8. The torsion angles of C7±C1±C6±C5 176.9(6)8

and C7±C1±C2±C3 2175.8(5)8 indicate that C7 is shifted

With intermolecular distances of C1´´´C4 3.812(8) A and

C6´´´C3⁰3.802(8) A a [212]photocycloaddition of the

Ê

for 0.070(8) A out of the quinone plane towards the diyne

quinone (CvC)-double bonds of neighboring molecules

must be taken into account, but the (C1vC6)- and

(C3⁰vC4⁰)- double bonds are shifted against each other in

direction parallel to C1±C6 by 1.79 A and vertical to C1±

Ê

C6 by 0.49 A resulting in an unfavorable orientation for a

photoinduced [212]cycloaddition in the solid-state.

unit. With a torsion angle of C2±C1±C7±C8 73.8(6)8 the

quinone substituent is nearly vertically oriented to the ethyl-

ene bridge. The ethylene unit shows a synclinal conforma-

tion in the crystal with a torsion angle of C1±C7±C8±C9

55.2(7)8.

Ê

Octa-3,5-diyne 4f in the crystal represents a stacking struc-

ture along the diagonal plane a,b (Fig. 10). The quinone

units of neighboring molecules are oriented parallel to

each other and are inclined to the stacking axis by 618.

The O1vC2±C3vC4 unit of one molecule is situated

congruent over the C4⁰vC3⁰±C2⁰vO1⁰group of an

adjacent molecule.

The solid-state irradiation product of 4f, obtained by irradia-

tion with UV light at l$254 nm for 3 h or l$520 nm for

8 h, showed oligomers of up to n3 in MALDI-TOF experi-

ments (Fig. 11). On the other hand, under thermal stress no

oligomers were observed. This suggests that no poly(but-1-

en-3-ynylene)s were produced by irradiation.

It is assumed that according to the topochemical parameters

obtained from X-ray diffraction analysis of 4f and the results

of frontier orbital correlation based on the model compound

E-3-chloroprop-2-ene-1-one, that a topochemical controlled

[212]cycloaddition of 4f under Paterno-BuÈchi^32,33had

taken place forming different oxetane-derivatives. Subse-

quent- and side-reactions are to be expected under the

selected reaction conditions leading to the formation of

further products.^34,35The exact constitution of the irradia-

tion products could not be determined, because of low yield

(2±3%) and problem in separation of the oligomers obtained

The relative position of two neighboring quinone units of 4f

seems to be mainly steered by attractive intermolecular

dipole±dipole interactions between C2±O1 and C4⁰±C3⁰

(Fig. 10) corresponding to the allocation of charge density

of the b-chloro-substituted vinyloge carbonyl unit Cl±

C4vC3±C2vO1. The resulting contacts have distances

of O1´´´C4 3.328(8) A and C2´´´C3 3.414(8) A. These

intermolecular distances are optimal for a topochemically

controlled [212]photocycloaddition according to Paterno-

BuÈchi.^32,33

0

Ê

Figure 11. MALDI-TOF-spectrum of the oligomers [4f]¹_n(n1±3) of octa-3,5-diyne 4f after UV irradiation (l$254 nm). The signal at m/z379

[(CCA)¹₂1H] is caused by the matrix CCA.

6788

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

3

by the irradiation. The quinone-substituted octa-3,5-diynes

4a±c, 4e and 4g showed no signi®cant thermo or photo

reactivity in the solid-state.

7.5 Hz, 2H, CH₂CH₂CCH); 2.52 (td, J_HH7.5 Hz,

4

⁴J_HH2.7 Hz, 2H, CH₂CH₂CCH); 1.86 (t, J_HH2.7 Hz,

1H, CH₂CH₂CCH). ¹³C NMR (75.5 MHz, C₆D₆): d 153.87

(COCH₃); 151.76 (COCH₃); 129.91 (CCH₂CH₂CCH);

116.61 (CH); 111.86 (CH); 111.05 (CH); 83.96

(CCH₂CH₂CCH); 68.90 (CCH₂CH₂CCH); 55.01 (s,

COCH₃); 54.96 (COCH₃); 30.22 (CCH₂CH₂±CCH); 18.98

(CCH₂CH₂CCH). MS (EI, 70 eV): m/z 190 (M¹, 68%); 151

([M¹2CH₂CCH], 100%). MS (HR, EI): M¹calcd:

190.0994, found: 190.0970. IR (KBr): n~ cm²¹3291 (s,

uC±H); 2116 (w, CuC).

Experimental

General

Melting points: BuÈchi Melting Point B-540 (Switzerland);

open capillary tube. IR: Bruker IFS 66. UV/Vis: HP 8452 A

(diode array). NMR: Bruker AC 300 (300 and 75.5 MHz,

for ¹H and ¹³C, respectively); chemical shifts are relative to

the solvent signal indicated (internal standard TMS). MS:

Finnigan 3200 (low-resolution electron ionization; 70 eV);

Vacuum Generators Micromass ZAB-2F (high-resolution

electron ionization; 70 eV); and Jeol JMS-700 (fast-atom

bombardment). Elemental analyses: Heraeus CHN-O-

Rapid.

4-(2,5-Dimethoxy-4-methylphenyl)-but-1-yne (2b). But-1-

yne 2b was obtained from 1b in 81% yield as a colorless

unstable liquid (bp_0.3101±1038C; n²_D⁰1.5350). H NMR

1

(300 MHz, CDCl₃): d 6.73 (s, 1H, 6H); 6.69 (s, 1H, 3-H);

3.80 (s, 3H, CH₃O); 3.78 (s, 3H, CH₃O); 2.84 (t,

3

³J_HH7.5 Hz, 2H, CH₂CH₂CCH); 2.48 (td, J_HH7.5 Hz,

⁴J_HH2.6 Hz, 2H, CH₂CH₂CCH); 2.23 (s, 3H, CCH₃);

1.99 (t, J_HH2.6 Hz, 1H, CH₂CH₂CCH). ¹³C NMR

4

Diethyl ether, dimethoxyethane (DME); tetrahydrofuran

(THF); and benzene were distilled from sodium benzo-

phenone ketyl in a recirculating still prior to use. Dichloro-

methane, cyclohexane, n-hexane, petroleum ether (30±75);

and tetramethylethylenediamine (tmeda) were distilled from

calcium hydride. All reagents were puri®ed according to

standard methods before use unless otherwise indicated.

All reactions were carried out under an inert atmosphere

of argon.

(75.5 MHz, C₆D₆): d 151.69 (COCH₃); 151.24 (COCH₃);

126.50 (CCH₃); 125.00 (CCH₂CH₂CCH); 113.68 (CH);

112.98

(CH);

84.25

(CCH₂CH₂CCH);

68.83

(CCH₂CH₂CCH); 55.27 (COCH₃); 55.20 (COCH₃); 30.15

(CCH₂CH₂±CCH); 19.34 (CCH₂CH₂CCH); 16.12 (CCH₃).

MS (EI, 70 eV): m/z 204 (M¹, 84%); 165 ([M¹2C₃H₃],

100%); 135 ([M¹2CH₂O], 37%). MS (HR, EI): M¹

calcd: 204.1150, found: 204.1173. IR (KBr): n~ cm²¹3292

(s, uC±H); 2116 (w, CuC).

The following compounds have been reported previously in

the literature and were prepared as described or according to

published procedures: 1-chloromethyl-2,5-dimethoxyben-

zene (1a),³⁶1-chloromethyl-2,5-dimethoxy-4-methylbenzene

(1b),³⁷2-bromomethyl-1,4-dimethoxy-5,6-dimethylbenzene

(1c),³⁸2-bromomethyl-1,4-dimethoxy-3,5,6-trimethylbenzene

(1d),^39,401-bromomethyl-4-¯uoro-2,5-dimethoxybenzene (1e),³⁸

1-bromomethyl-4-chloro-2,5-dimethoxybenzol (1f)⁴¹and

1-bromo-4-bromomethyl-2,5-dimethoxybenzene (1g).³⁸Prop-

2-yne-1-yl magnesium bromide was prepared from

3-bromoprop-1-yne (80% solution in toluene; purchased

from Aldrich and used without further puri®cation) and

magnesium-turnings.¹⁰

4-(2,5-Dimethoxy-3,4-dimethylphenyl)-but-1-yne (2c). But-

1-yne 2c was obtained from 1c in 52% yield as a colorless

unstable liquid (bp_0.16948C; n²_D⁰1.5294). ¹H NMR

(300 MHz, CDCl₃): d 6.62 (s, 1H, 6-H); 3.80 (s, 3H,

3

CH₃O); 3.68 (s, 3H, CH₃O); 2.87 (t, J_HH7.6 Hz, 2H,

3

4

CH₂CH₂CCH); 2.51 (td, J_HH7.6 Hz, J_HH2.7 Hz, 2H,

CH₂CH₂CCH); 2.21 (s, 3H, CCH₃); 2.13 (s, 3H, CCH₃);

4

2.01 (t, J_HH2.7 Hz, 2H, CH₂CH₂CCH). ¹³C NMR

(75.5 MHz, CDCl₃): d 153.56 (COCH₃); 150.29 (COCH₃);

130.76 (CCH₃); 130.14 (CCH₃); 124.76 (CCH₂CH₂CCH);

109.28

(CH);

84.30

(CCH₂CH₂CCH);

68.63

(CCH₂CH₂CCH); 60.87 (COCH₃); 55.70 (COCH₃); 29.55

(CCH₂CH₂CCH); 19.80 (CCH₂CH₂CCH); 12.74 (CCH₃);

11.87 (CCH₃). MS (EI, 70 eV): m/z 218 (M¹, 88%); 203

([M¹2CH₃], 20%); 179 ([M¹2C₃H₃], 100%). MS (HR,

EI): M¹calcd: 218.1307, found: 218.1319. IR (NaCl): n~

cm²¹3289 (s, uC±H); 2117 (w, CuC).

General procedure for the synthesis of but-1-ynes 2a±g

To a solution of 1 (10 mmol) in 300 ml diethyl ether was

added dropwise a solution of freshly prepared prop-2-yne-1-

yl magnesium bromide (20 mmol) in 40 ml diethyl ether

over a period of 30 min. After complete addition the reac-

tion mixture was stirred at room temperature for one day,

then poured into 200 ml ice water. The organic phase was

separated and the watery phase extracted with diethyl ether

(3£100 ml). The combined organic phases were dried over

magnesium sulfate, concentrated under reduced pressure,

and the residue was puri®ed by distillation.

4-(2,5-Dimethoxy-3,4,6-trimethylphenyl)-but-1-yne (2d).

But-1-yne 2d was obtained from 1d in 49% yield as a color-

less unstable solid (mp 36.18C). ¹H NMR (300 MHz,

CDCl₃): d 3.67 (s, 3H, CH₃O); 3.62 (s, 3H, CH₃O); 2.88

(t, ³J_HH7.8 Hz, 2H, CH₂CH₂CCH); 2.35 (td, ³J_HH7.8 Hz,

⁴J_HH2.6 Hz, 2H, CH₂CH₂CCH); 2.23 (s, 3H, 6-CCH₃);

4

2.16 (s, 6H, 3,4-CCH₃); 1.98 (t, J_HH2.6 Hz, 2H,

CH₂CH₂CCH). ¹³C NMR (75.5 MHz, CDCl₃): d 152.84

(COCH₃); 152.79 (COCH₃); 130.05 (CCH₂±CH₂CCH);

128.82 (CCH₃); 127.82 (CCH₃); 127.18 (CCH₃); 84.26

4-(2,5-Dimethoxyphenyl)-but-1-yne (2a). But-1-yne 2a

was obtained from 1a in 23% yield as a colorless unstable

liquid (bp_0.594±968C). H NMR (300 MHz, C₆D₆): d 6.89

(CCH₂CH₂CCH);

68.06

(CCH₂CH₂CCH);

60.69

1

(COCH₃); 59.83 (COCH₃); 26.61 (CCH₂±CH₂CCH);

18.89 (CCH₂CH₂CCH); 12.62 (CCH₃); 12.50 (CCH₃);

11.96 (6-CCH₃). MS (EI, 70 eV): m/z 232 (M¹, 65%); 217

([M¹2CH₃], 14%); 193 ([M¹2C₃H₃], 100%). MS (HR,

4

3

(d, J_HH3.1 Hz, 1H, 6-H); 6.75 (dd, J_HH8.8 Hz,

⁴J_HH3.1 Hz, 1H, 4H); 6.54 (d, J_HH8.8 Hz, 1H, 3-H);

3

3.48 (s, 3H, CH₃O); 3.36 (s, 3H, CH₃O); 2.98 (t, J_HH

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6789

EI): M¹calcd: 232.1463, found: 232.1472. IR (KBr): n~

cm²¹3307 (s, uC±H); 2115 (w, CuC).

368C, a stream of oxygen was passed through the mixture

for one to two days. The reaction mixture was then poured

into 300 ml water. The resulting precipitate was ®ltered off

and recrystallized twice from the corresponding solvent (cf.

mp).

4-(4-Fluoro-2,5-dimethoxyphenyl)-but-1-yne (2e). But-1-

yne 2e was obtained from 1e in 59% yield as a colorless

unstable liquid which solidi®es on standing (bp_0.07105±

1

1078C; mp 548C). H NMR (300 MHz, C₆D₆): d 6.70 (d,

1,8-Bis(2,5-dimethoxyphenyl)-octa-3,5-diyne (3a). Octa-

3,5-diyne 3a was obtained from 2a in 34% yield as a color-

less solid (mp 79±808C; n-hexane). H NMR (300 MHz,

3

⁴J_HF9.5 Hz, 1H, 6-H); 6.47 (d, J_HF12.8 Hz, 1H, 3-H);

1

3.50 (s, 3H, CH₃O); 3.14 (s, 3H, CH₃O); 2.86 (t,

3

4

3

³J_HH7.5 Hz, 2H, CH₂CH₂CCH); 2.45 (td, J_HH7.5 Hz,

C₆D₆): d 6.84 (d, J_HH3.0 Hz, 2H, 6-H); 6.75 (dd, J_HH

4

3

⁴J_HH2.6 Hz, 2H, CH₂CH₂CCH); 1.88 (t, J_HH2.6 Hz,

8.8 Hz, J_HH3.0 Hz, 2H, 4H); 6.54 (d, J_HH8.8 Hz, 2H,

2H, CH₂CH₂CCH). ¹³C NMR (75.5 MHz, C₆D₆): d 151.96

3-H); 3.50 (s, 6H, CH₃O); 3.36 (s, 6H, CH₃O); 2.88 (t,

(d, ¹J_CF244.3 Hz, CF); 151.45 (d, ³J_CF7.8 Hz, 2COCH₃);

³J_HH7.5 Hz, 4H, CH₂CH₂CC); 2.49 (t, J_HH7.5 Hz, 4H,

3

2

4

141.14 (d, J_CF10.8 Hz, 5-COCH₃); 123.88 (d, J_CF

CH₂CH₂CC). ¹³C NMR (75.5 MHz, CDCl₃): d 154.07

(COCH₃); 151.90 (COCH₃); 129.86 (CCH₂CC); 116.57

(3-CH); 112.36 (6-CH); 111.31 (4CH); 77.48 (CH₂CH₂CC);

67.05 (CH₂CH₂CC); 55.25 (COCH₃); 55.21 (COCH₃);

30.17 (CCH₂CH₂CC); 20.05 (CCH₂CH₂CC). MS (EI,

70 eV): m/z 378 (M¹, 26%); 151 ([C₆H₃(OCH₃)₂CH₂]¹,

100%). MS (HR, EI): M¹calcd: 378.1831, found:

378.1835. IR (KBr): n~ cm²¹2149 (w, CuC). UV/Vis

(CH₂Cl₂): l nm (e) 226 (18220); 292 (10445). Anal.

calcd for C₂₄H₂₆O₄: C 76.17%, H 6.93%; found: C

76.04%, H 7.07%.

3

3.8 Hz, CCH₂CH₂CC); 116.99 (d, J_CF3.0 Hz, 6CH);

2

100.41 (d, J_CF22.1 Hz, 3-CH); 83.79 (CCH₂CH₂CCH);

69.05 (CCH₂CH₂CCH); 56.71 (COCH₃); 55.00 (COCH₃);

29.55 (CCH₂CH₂CCH); 19.06 (CCH₂CH₂CCH). MS (EI,

70 eV): m/z 208 (M¹, 33%); 169 ([M¹2C₃H₃], 100%).

MS (HR, EI): M¹calcd: 208.0900, found: 208.0927. IR

(KBr): n~ cm²¹3287 (s, uC±H); 2114 (w, CuC).

4-(4-Chloro-2,5-dimethoxyphenyl)-but-1-yne (2f). But-1-

yne 2f was obtained from 1f in 41% yield as a colorless

unstable liquid which solidi®es on standing (bp_0.17838C;

mp 548C). ¹H NMR (300 MHz, C₆D₆): d 6.80 (s, 1H,

3-H); 6.60 (s, 1H, 6H); 3.44 (s, 3H, CH₃O); 3.14 (s, 3H,

1,8-Bis(2,5-dimethoxy-4-methylphenyl)-octa-3,5-diyne

(3b). Octa-3,5-diyne 3b was obtained from 2b in 85% yield

as colorless plates crystallizing in two modi®cations [mp

3

CH₃O); 2.85 (t, J_HH7.5 Hz, 2H, CH₂CH₂CCH); 2.44 (td,

4

1

³J_HH7.5 Hz, J_HH2.7 Hz, 2H, CH₂CH₂CCH); 1.87 (t,

114.48C (ethanol) and mp 113.48C (methanol)]. H NMR

(500 MHz, C₆D₆): d 6.54 (s, 2H, 6-H); 6.47 (s, 2H, 3-H);

3.44 (s, 6H, 2-CH₃O); 3.29 (s, 6H, 5CH₃O); 2.84 (t,

⁴J_HH2.7 Hz, 1H, CH₂CH₂CCH). ¹³C NMR (75.5 MHz,

CDCl₃): d 151.55 (COCH₃); 149.07 (COCH₃); 128.09

(CCH₂CH₂CCH); 120.39 (4-CCl); 115.15 (6-CH); 113.01

(3CH); 84.03 (CCH₂CH₂CCH); 68.83 (CCH₂CH₂CCH);

56.89 (COCH₃); 55.97 (COCH₃); 29.66 (CCH₂CH₂±

CCH); 18.78 (CCH₂CH₂CCH). MS (EI, 70 eV): m/z 224

(M¹, 32%); 185 ([M¹2CH₂CCH], 100%). MS (HR, EI):

M¹calcd: 224.0604, found: 224.0604. IR (KBr-Film): n~

cm²¹3274 (s, uC±H); 2111 (w, CuC).

3

³J_HH7.3 Hz, 4H, CH₂CH₂CC); 2.45 (t, J_HH7.3 Hz, 4H,

CH₂CH₂CC); 2.28 (s, 6H, CCH₃). ¹³C NMR (125.8 MHz,

C₆D₆): d 151.63 (COCH₃); 151.07 (COCH₃); 126.21

(4-CCH₃); 124.98 (CCH₂CH₂CuC); 113.56 (3-CH);

112.76

(6CH);

77.45

(CH₂CH₂CuC);

66.86

(CH₂CH₂CuC); 55.21 (COCH₃); 55.11 (COCH₃); 29.86

(CCH₂CH₂CuC); 20.18 (CCH₂CH₂CuC); 16.24 (4-

CCH₃). MS (EI, 70 eV): m/z 406 (M¹, 30%); 165

([C₆H₂(CH₃)(OCH₃)₂CH₂]¹, 100%). MS (HR, EI): M¹

calcd: 406.2159, found: 406.2144. IR (KBr): n~ cm²¹2155

(w, CuC). UV/Vis (CH₂Cl₂): l nm (e) 224 (18850); 292

(9957). Anal. calcd for C₂₆H₃₀O₄: C 76.82%, H 7.44%;

found: C 76.66%, H 7.50%.

4-(4-Brom-2,5-dimethoxyphenyl)-but-1-yne (2g). But-1-

yne 2g was obtained from 1g in 40% yield as a colorless

unstable liquid which solidi®es on standing (bp_0.02108±

1098C; mp 43±458C). ¹H NMR (300 MHz, CDCl₃): d

7.00 (s, 1H, 3-H); 6.78 (s, 1H, 6H); 3.82 (s, 3H, CH₃O);

3

3.75 (s, 3H, CH₃O); 2.78 (t, J_HH7.4 Hz, 2H,

3

4

CH₂CH₂CCH); 2.43 (td, J_HH7.4 Hz, J_HH2.6 Hz, 2H,

1,8-Bis(2,5-dimethoxy-3,4-dimethylphenyl)-octa-3,5-

diyne (3c). Octa-3,5-diyne 3c was obtained from 2c in 81%

yield as colorless light-sensitive needles (mp 130.98C;

4

CH₂CH₂CCH); 1.94 (t, J_HH2.6 Hz, 1H, CH₂CH₂CCH).

¹³C NMR (75.5 MHz, CDCl₃): d 151.64 (COCH₃); 149.59

(COCH₃); 128.70 (CCH₂CH₂CCH); 116.52 (3-CH); 114.77

(6CH); 109.06 (4-CBr); 83.77 (CCH₂CH₂CCH); 68.63

(CCH₂CH₂±CCH); 56.76 (COCH₃); 55.80 (COCH₃);

29.51 (CCH₂CH₂CCH); 18.47 (CCH₂CH₂CCH). MS (EI,

70 eV): m/z 270 ([M12]¹, 58%); 268 (M¹, 61%); 229

([M¹2CH₂CCH], 100%); 199 ([M¹2CH₂CCH±CH₂O]¹,

37%). MS (HR, EI): M¹calcd: 268.0099, found: 268.0101.

IR (KBr): n~ cm²¹3294 (s, uC±H); 2113 (w, CuC).

1

n-hexane). H NMR (300 MHz, CDCl₃): d 6.58 (s, 2H,

6-H); 3.78 (s, 6H, CH₃O); 3.65 (s, 6H, CH₃O); 2.83 (t,

3

³J_HH7.5 Hz, 4H, CH₂CH₂CC); 2.53 (t, J_HH7.5 Hz, 4H,

CH₂CH₂CC); 2.19 (s, 6H, CCH₃); 2.11 (s, 6H, CCH₃). ¹³C

NMR (75.5 MHz, CDCl₃): d 153.42 (COCH₃); 150.11

(COCH₃); 130.62 (CCH₃); 129.72 (CCH₃); 124.72

(CCH₂CH₂CC); 109.22 (6-CH); 77.22 (CH₂CH₂CC);

65.74 (CH₂CH₂CC); 60.75 (COCH₃); 55.60 (COCH₃);

29.26 (CCH₂CH₂CC); 20.53 (CCH₂CH₂CC); 12.58

(CCH₃); 11.71 (CCH₃). MS (EI, 70 eV): m/z 434 (M¹,

28%); 179 ([C₆H(CH₃)₂(OCH₃)₂CH₂]¹, 100%). MS (HR,

EI): M¹calcd: 434.2457, found: 434.2455. IR (KBr): n~

cm²¹2146 (w, CuC). UV/Vis (CH₂Cl₂): l nm (e) 234

(9585); 286 (5630). Anal. calcd for C₂₈H₃₄O₄: C 77.39%,

H 7.89%; found: C 77.29%, H 7.87%.

General procedure for the synthesis of octa-3,5-diynes

3a±g

To a solution of 3 (20 mmol) in 10 ml DME, a suspension of

0.594 g (6 mmol) copper(I) chloride and 1.046 g (9 mmol)

tmeda in 40 ml DME was slowly added at 30±358C. At 35±

6790

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

3

1,8-Bis(2,5-dimethoxy-3,4,6-trimethylphenyl)-octa-3,5-

diyne (3d). Octa-3,5-diyne 3d was obtained from 2b in 52%

³J_HH7.3 Hz, 4H, CH₂CH₂CC); 2.47 (t, J_HH7.3 Hz, 4H,

CH₂CH₂CC). ¹³C NMR (75.5 MHz, CDCl₃): d 151.50

(COCH₃); 149.52 (COCH₃); 128.31 (CCH₂CC); 115.47

(3-CH); 114.66 (6CH); 109.06 (4-CBr); 76.90

(CH₂CH₂CC); 65.76 (CH₂CH₂CC); 56.71 (COCH₃); 55.73

(COCH₃); 29.24 (CCH₂CH₂CC); 19.29 (CCH₂CH₂CC). MS

(EI, 70 eV): m/z 538 ([M14]¹, 17%); 536 ([M12]¹, 34%);

534 (M¹, 18%); 229 ([C₆H₂(Br⁷⁹)(OCH₃)₂CH₂]¹, 100%).

MS (HR, EI): M¹calcd: 534.0041, found: 534.0003. IR

(KBr): n~ cm²¹2159 (w, CuC). UV/Vis (CH₂Cl₂): l nm

(e) 224 (29480); 296 (14157). Anal. calcd for C₂₄H₂₄Br₂O₄:

C 53.75%, H 4.51%; found: C 53.86%, H 4.62%.

1

yield as colorless thin plates (mp 161.18C; n-hexane). H

NMR (300 MHz, CDCl₃): d 3.65 (s, 6H, CH₃O); 3.62 (s,

6H, CH₃O); 2.87 (t, ³J_HH7.6 Hz, 4H, CH₂CH₂CC); 2.40 (t,

³J_HH7.6 Hz, 4H, CH₂CH₂CC); 2.23 (s, 6H, 6-CCH₃); 2.16

(s, 6H, 4-CCH₃); 2.15 (s, 6H, 3-CCH₃). ¹³C NMR

(125.8 MHz, C₆D₆): d 153.09 (COCH₃); 152.99 (COCH₃);

130.04 (CCH₃); 129.14 (CCH₃); 128.08 (CCH₃); 127.41

(CCH₂CC); 77.56 (CH₂CH₂CC); 65.49 (CH₂CH₂CC);

60.92 (COCH₃); 60.08 (COCH₃); 26.69 (CCH₂CH₂CC);

19.96 (CCH₂CH₂CC); 12.84 (CCH₃); 12.73 (CCH₃); 12.19

(CCH₃). MS (EI, 70 eV): m/z 462 (M¹, 18%); 193

([C₆H(CH₃)₃(OCH₃)₂CH₂]¹, 100%). MS (HR, EI): M¹

calcd: 462.2770, found: 462.2752. IR (KBr): n~ cm²¹2148

(w, CuC). UV/VIS (CH₂Cl₂): l nm (e) 234 (7016); 258

(984); 274 (1651); 280 (1762). Anal. calcd for C₃₀H₃₈O₄: C

77.89%, H 8.28%; found: C 77.65%, H 8.29%.

General procedure for the synthesis of octa-3,5-diynes

4a±g

To a stirred solution of 3 (300 mmol) in 40 ml acetonitrile at

25±308C a solution of CAN (2.4 mmol) in 5 ml water was

added in 1 ml portions. After stirring for 45 min, 30 ml of

dichloromethane was added and the reaction mixture was

then poured into 250 ml ice water. The organic phase was

separated and the watery phase was extracted with dichloro-

methane (3£20 ml). The combined organic phases were

dried over magnesium sulfate, the solvent was evaporated

in vacuo, the residue dissolved in 3 ml toluene, and the

resulting yellow solution was ®ltered through silica gel.

The solvent was removed under reduced pressure and the

residue was recrystallized twice from benzene or toluene.

1,8-Bis(4-¯uoro-2,5-dimethoxyphenyl)-octa-3,5-diyne

(3e). Octa-3,5-diyne 3e was obtained from 2e in 85% yield

as colorless needles (mp 98.28C; methanol). ¹H NMR

4

(300 MHz, C₆D₆): d 6.68 (d, J_HF9.5 Hz, 1H, 6-H); 6.46

3

(d, J_HF12.8 Hz, 1H, 3-H); 3.54 (s, 3H, CH₃O); 3.15 (s,

3H, CH₃O); 2.78 (t, ³J_HH7.3 Hz, 2H, CH₂CH₂CC); 2.44 (t,

³J_HH7.3 Hz, 2H, CH₂CH₂CC). ¹³C NMR (75.5 MHz,

1

C₆D₆): d 152.23 (d, J_CF244.5 Hz, CF); 151.64 (d,

³J_CF7.8 Hz, 2COCH₃); 141.44 (d, ²J_CF10.8 Hz,

4

5-COCH₃); 123.82 (d, J_CF3.8 Hz, CCH₂CH₂CC);

3

2

117.14 (d, J_CF3.0 Hz, 6CH); 100.69 (d, J_CF22.1 Hz,

3-CH); 77.45 (CCH₂CH₂CCH); 67.13 (CCH₂CH₂CCH);

56.96 (COCH₃); 55.28 (COCH₃); 29.51 (CCH₂CH₂CCH);

20.01 (CCH₂CH₂CCH). MS (EI, 70 eV): m/z 414 (M¹,

30%); 169 ([C₆H₂(F)(OCH₃)₂CH₂]¹, 100%). MS (HR, EI):

M¹calcd: 414.1643, found: 414.1646. IR (KBr): n~ cm²¹

2149 (br. w, CuC). UV/Vis (CH₂Cl₂): l nm (e) 226

(15709); 288 (8422). Anal. calcd for C₂₄H₂₄F₂O₄: C

69.55%, H 5.84%; found: C 69.36%, H 5.85%.

1,8-Bis(3,6-dioxocyclohexa-1,4-dienyl)-octa-3,5-diyne

(4a). Quinone 4a was obtained from 3a in 8% yield as

1

yellow needles (mp 132.6±132.78C; benzene). H NMR

(300 MHz, C₆D₆): d 6.20 (s, 2H, 2-CH); 6.08 (s, 2H,

3

4-CH); 6.07 (s, 2H, 5-CH); 2.15 (t, J_HH6.8 Hz, 4H,

CH₂CH₂CC); 2.04 (t, J_HH6.8 Hz, 4H, CH₂CH₂CC). ¹³C

3

NMR (125.8 MHz, CDCl₃): d 187.34 (CO); 186.99 (CO);

146.39 (CCH₂CC); 136.64 (5-CH); 136.46 (2-CH); 133.52

(4-CH); 75.70 (CH₂CH₂CC); 66.73 (CH₂CH₂CC); 28.02

(CCH₂CH₂CC); 17.88 (CCH₂CH₂CC). MS (EI, 70 eV):

m/z 318 (M¹, 34%); 236 ([M¹2C₄H₂O₂], 54%); 123

([C₇H₇O₂]¹, 100%). MS (HR, EI): M¹calcd: 318.0892,

found: 318.0866. IR (KBr): n~ cm²¹2150 (w, CuC); 1655

(s, CvO) 1598 (m, CvC). UV/Vis (CH₂Cl₂): l nm (e) 248

(36884); 300 (2620). Anal. calcd for C₂₀H₁₄O₄: C 75.46%, H

4.43%; found: C 75.17%, H 4.62%.

1,8-Bis(4-chloro-2,5-dimethoxyphenyl)-octa-3,5-diyne

(3f). Octa-3,5-diyne 3f was obtained from 2b in 48% yield

as colorless needles (mp 1518C; benzene). ¹H NMR

(300 MHz, C₆D₆): d 6.68 (s, 2H, 3-H); 6.49 (s, 2H, 6-H);

3.39 (s, 6H, 2-CH₃O); 3.05 (s, 6H, 5CH₃O); 2.66 (t,

3

³J_HH7.3 Hz, 4H, CH₂CH₂CC); 2.32 (t, J_HH7.3 Hz, 4H,

CH₂CH₂CC). ¹³C NMR (75.5 MHz, C₆D₆): d 151.44

(COCH₃); 148.69 (COCH₃); 127.74 (CCH₂CC); 120.42

(4-CCl); 115.07 (6-CH); 112.83 (3CH); 77.20

(CH₂CH₂CC); 65.99 (CH₂CH₂CC); 56.86 (2COCH₃);

55.94 (5-COCH₃); 29.44 (CCH₂CH₂CC); 19.65

(CCH₂CH₂CC). MS (EI, 70 eV): m/z 448 ([M12]¹, 9%);

446 (M¹, 13%); 185 ([C₆H₂(Cl³⁵) (OCH₃)₂CH₂]¹, 100%).

MS (HR, EI): M¹calcd: 446.1052, found: 446.1046. IR

(KBr): n~ cm²¹2160 (w, CuC). UV/VIS (CH₂Cl₂): l nm

(e) 230 (17998); 296 (10704). Anal. calcd for C₂₄H₂₄Cl₂O₄:

C 64.44%, H 5.41%, Cl 15.85%; found: C 64.38%, H

5.37%, Cl 15.92%.

1,8-Bis(4-methyl-3,6-dioxocyclohexa-1,4-dienyl)-octa-3,5-

diyne (4b). Quinone 4b was obtained from 3b in 84% yield

as yellow plates (mp 132±1338C; benzene). ¹H NMR

(300 MHz, C₆D₆):

d 6.15 (s, 2H, 2-H); 5.98 (q,

⁴J_HH1.5 Hz, 2H, 5-H); 1.97 (t, J_HH6.8 Hz, 4H,

3

CH₂CH₂CC); 1.89 (t, J_HH6.8 Hz, 4H, CH₂CH₂CC); 1.51

(d, ⁴J_HH1.5 Hz, 6H, CCH₃). ¹³C NMR (125.8 MHz, C₆D₆):

d 187.25 (CO); 186.79 (CO); 145.93 (CCH₂CC); 145.23

(4-CCH₃); 133.30 (CH); 133.18 (CH); 76.51 (CH₂CH₂CC);

67.52 (CH₂CH₂CC); 27.81 (CCH₂CH₂CC); 17.87

(CCH₂CH₂CC); 15.08 (4-CCH₃). MS (EI, 70 eV): m/z 346

(M¹, 40%); 211 ([M¹2C₆H₂(CH₃)(O)₂CH₂], 45%); 137

([C₆H₂(CH₃)(O)₂CH₂12H]¹, 100%). MS (HR, EI): M¹

calcd: 346.1205, found: 346.1215. IR (KBr): n~ cm²¹2147

(w, CuC); 1649 (vs, CvO) 1614 (m, CvC). UV/Vis

(CH₂Cl₂): l nm (e) 254 (32341); 262 (27392); 280

1,8-Bis(4-bromo-2,5-dimethoxyphenyl)-octa-3,5-diyne

(3g). Octa-3,5-diyne 3g was obtained from 2g in 74% yield

1

as colorless crystals (mp 1568C; cyclohexane). H NMR

(300 MHz, CDCl₃): d 6.99 (s, 2H, 3-H); 6.76 (s, 2H,

6-H); 3.82 (s, 6H, CH₃O); 3.75 (s, 6H, CH₃O); 2.76 (t,

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6791

(10704). Anal. calcd for C₂₂H₁₈O₄: C 76.29%, H 5.24%;

found: C 75.70%, H 5.24%.

diyne (4f). Quinone 4f was obtained from 3f in 38% yield as

yellow needles (mp 132±1338C; benzene). ¹H NMR

(300 MHz, CDCl₃): d 6.98 (s, 2H, 5-H); 6.78 (s, 2H,

3

1,8-Bis(4,5-dimethyl-3,6-dioxocyclohexa-1,4-dienyl)-octa-

3,5-diyne (4c). Quinone 4c was obtained from 3c in 66%

2-H); 2.63 (t, J_HH6.5 Hz, 4H, CH₂CH₂CC); 2.51 (t,

³J_HH6.5 Hz, 4H, CH₂CH₂CC). ¹³C NMR (75.5 MHz,

CDCl₃): d 184.56 (CO); 179.18 (CO); 146.92 (CCH₂CC);

143.88 (4-CCl); 133.46 (CH); 132.54 (CH); 75.41

(CH₂CH₂CC); 66.77 (CH₂CH₂CC); 27.65 (CCH₂CH₂CC);

17.73 (CCH₂CH₂CC). MS (EI, 70 eV): m/z 386 (M¹,

16%); 231 ([M¹2C₆H₂(Cl³⁵)(O)₂CH₂], 44%); 157

([C₆H₂(Cl³⁵)(O)₂CH₂12H]¹, 100%). MS (HR, EI): M¹

calcd: 386.0113, found: 386.0131. IR (KBr): n~ cm²¹2149

(w, CuC); 1666 (vs, CvO) 1596 (m, CvC). UV/Vis

(CH₂Cl₂):l nm (e) 260 (33775); 264 (33775); 292 (5308).

Anal. calcd for (C₂₀H₁₂Cl₂O₄)₂´´´C₆H₅CH₃: C 65.14%, H

3.72%, Cl 16.36%; found: C 65.02%, H 3.94%, Cl 15.91%.

1

yield as yellow crystals (mp 88.9±89.28C; toluene). H

NMR (500 MHz, CDCl₃): d 6.59 (s, 2H, 2-H); 2.62 (t,

3

³J_HH6.8 Hz, 4H, CH₂CH₂CC); 2.50 (t, J_HH6.8 Hz, 4H,

CH₂CH₂CC); 2.02 (s, 12H, 4-CCH₃, 5-CCH₃). ¹³C NMR

(125.8 MHz, CDCl₃): d 187.35 (CO); 187.17 (CO);

145.96 (CCH₂CC); 141.05 (CCH₃); 140.45 (CCH₃);

133.29 (CH); 75.98 (CH₂CH₂CC); 66.67 (CH₂CH₂CC);

28.26 (CCH₂CH₂CC); 18.05 (CCH₂CH₂CC); 12.38

(CCH₃); 12.11 (CCH₃). MS (EI, 70 eV): m/z 374 (M¹,

52%); 225 ([M¹2C₆H(CH₃)₂(O)₂CH₂], 50%); 151

([C₆H(CH₃)₂(O)₂CH₂12H]¹, 100%). MS (HR, EI): M¹

calcd: 374.1518, found: 374.1496. IR (KBr): n~ cm²¹2148

(w, CuC); 1650 (vs, CvO); 1613 (m, CvC). UV/Vis

(CH₂Cl₂): l nm (e) 258 (33861); 330 (1206). Anal. calcd

for C₂₄H₂₂O₄: C 76.99%, H 5.92%; found: C 76.73%, H

5.91%.

1,8-Bis(4-bromo-3,6-dioxocyclohexa-1,4-dienyl)-octa-3,5-

diyne (4g). Quinone 4g was obtained from 3g in 17% yield

as yellow needles (mp 141.88C; benzene). ¹H NMR

(300 MHz, C₆D₆): d 6.51 (s, 2H, 5-H); 6.06 (s, 2H, 2-H);

3

1.96 (t, J_HH6.5 Hz, 4H, CH₂CH₂CC); 1.88 (t,

1,8-Bis(2,4,5-trimethyl-3,6-dioxocyclohexa-1,4-dienyl)-

octa-3,5-diyne (4d). Quinone 4d was obtained from 3d in

85% yield as yellow light-sensitive needles (mp 122.2±

³J_HH6.5 Hz, 4H, CH₂CH₂CC). ¹³C NMR (75.5 MHz,

C₆D₆): d 183.83 (CO); 178.73 (CO); 146.08 (CCH₂CC);

137.85 (5-CH); 137.07 (4-CBr); 132.24 (2-CH); 76.39

(CH₂CH₂CC); 67.54 (CH₂CH₂CC); 27.69 (CCH₂CH₂CC);

17.58 (CCH₂CH₂CC). MS (EI, 70 eV): m/z 478 ([M14]¹,

8%); 476 ([M12]¹, 17%); 474 (M¹, 13%); 275

([M¹2C₆H₂(Br⁷⁹)(O)₂CH₂], 33%); 157 ([C₆H₂(Br⁷⁹)

(O)₂CH₂12H]¹, 63%); 78 ([C₆H₆]¹, 100%). MS (HR, EI):

M¹calcd: 386.0113, found: 386.0131. IR (KBr): n~ cm²¹

2157 (w, CuC); 1667 (vs, CvO) 1590 (m, CvC). UV/Vis

(CH₂Cl₂): l nm (e) 268 (20250). Anal. calcd for

C₂₀H₁₂Br₂O₄: C 50.45%, H 2.54%, Br 33.57%; found: C

50.32%, H 2.78%, Br 33.13%.

1

122.78C; benzene). H NMR (300 MHz, C₆D₆): d 2.36 (t,

3

³J_HH6.8 Hz, 4H, CH₂CH₂CC); 2.17 (t, J_HH6.8 Hz, 4H,

CH₂CH₂CC); 1.84 (s, 6H, CCH₃); 1.64 (s, 12H, CCH₃). ¹³

C

NMR (75.5 MHz, C₆D₆): d 186.87 (CO); 186.37 (CO);

141.73 (CCH₂CC); 141.25 (CCH₃); 140.45 (CCH₃);

140.08 (CCH₃); 77.00 (CH₂CH₂CC); 67.11 (CH₂CH₂CC);

25.67 (CCH₂CH₂CC); 18.77 (CCH₂CH₂CC); 12.37

(CCH₃); 12.09 (CCH₃); 11.91 (CCH₃). MS (EI, 70 eV):

m/z 402 (M¹, 100%); 387 ([M¹2CH₃], 30%);

239

([M¹2C₆(CH₃)₃(O)₂CH₂],

40%);

165

([C₆(CH₃)₃(O)₂CH₂12H]¹, 57%). MS (HR, EI): M¹

calcd: 402.1831, found: 402.1821. IR (KBr): n~ cm²¹2159

(w, CuC); 1642 (vs, CvO); 1625 (w, CvC). UV/Vis

(CH₂Cl₂): l nm (e) 262 (33262). Anal. calcd for

C₂₆H₂₆O₄: C 77.59%, H 6.51%; found: C 77.46%, H 6.46%.

all-E-Poly{1,2-bis[2-(2,5-dimethoxy-3,4-dimethylphenyl)-

ethyl]-but-1-en-3-ynylene} (5). A crystalline sample of

57.2 mg (131.3 mmol) 3c was irradiated with UV light

(l$254 nm) for 40 h at 158C. To remove unreacted mono-

mer, the orange solid was extracted with boiling THF for 3 h

and then dried in vacuo to yield 21.1 mg (37%) of 5 as a

orange-bronze solid (mp .3208C). MS (FD): m/z 1736

[(C₂₈H₃₄O₄)¹₄, ,1%], 1302 [(C₂₈H₃₄O₄)¹₃, 1%], 868

[(C₂₈H₃₄O₄)¹₂, 8%], 434 (C₂₆H₂₆O¹₄, 100%). IR (KBr): n~

cm²¹2990 (m); 2940 (m); 2864 (m); 2834 (m); 2146 (w,

CuC); 1624 (w); 1585 (w); 1484 (m); 1468 (s); 1409 (s);

1379 (w); 1342 (w); 1317 (m); 1254 (m); 1230 (vs); 1189

(s); 1119 (s); 1093 (s); 1018 (m); 841 (m); 689 (m). Raman

(solid): n~ cm ²¹2109 (s, CuC); 1489 (m, CvC).

1,8-Bis(4-¯uoro-3,6-dioxocyclohexa-1,4-dienyl)-octa-3,5-

diyne (4e). Quinone 4e was obtained from 3e in 12% yield

1

as yellow thin needles (mp 166.2±167.18C; benzene). H

4

NMR (300 MHz, C₆D₆): 6.03

d

(dt, J_HF8.6 Hz,

⁴J_HH1.3 Hz, 2H, 2-H); 5.65 (d, J_HF9.7 Hz, 2H, 5-H);

3

4

2.08 (td, J_HH6.3 Hz, J_HH1.3 Hz, 4H, CH₂CH₂CC);

2.00 (t, J_HH6.3 Hz, 4H, CH₂CH₂CC). ¹³C NMR

3

(75.5 MHz, C₆D₆): d 186.21 (d, J_CF14.0 Hz, 6-CO);

179.95 (d, ²J_CF23.9 Hz, 3-CO); 159.38 (d,

¹J_CF292.8 Hz, 4-CF); 146.41 (CCH₂CC); 131.10 (d,

³J_CF3.1 Hz, 2-CH); 114.67 (d, J_CF8.4 Hz, 5-CH);

all-E-Poly{1,2-bis[2-(2,4,5-trimethyl-3,6-dioxocyclohexa-

1,4-dienyl)-ethyl]-but-1-en-3-ynylene} (6).

2

76.38 (CH₂CH₂CC); 67.56 (CH₂CH₂CC); 27.69

(CCH₂CH₂CC); 17.72 (CCH₂CH₂CC). MS (EI, 70 eV):

m/z 354 (M¹, 6%); 215 ([M¹2C₆H₂(F)(O)₂CH₂], 24%);

141 ([C₆H₂(F)(O)₂CH₂12H]¹, 100%). MS (HR, FAB):

M¹calcd: 354.0704, found: 354.0730. IR (KBr): n~ cm²¹

2147 (br. w, CuC); 1660 (vs, CvO) 1620 (m, CvC). UV/

Vis (CH₂Cl₂): l nm (e) 252 (38811); 258 (35504); 286

(3165). Anal. calcd for C₂₀H₁₂F₂O₄: C 67.80%, H 3.41%;

found: C 68.08%, H 3.62%.

A

®nely

powdered sample of 60.3 mg (149.2 mmol) 4d was

irradiated with UV light (l$254 nm) for 3 h at 158C. To

remove unreacted monomer, the intensive-blue solid was

extracted with ethyl acetate for 2 h and then dried in

vacuo to yield 18.1 mg (30%) of 6 as a red solid (mp

.3208C). MS (FD): m/z 1608 [(C₂₆H₂₆O₄)¹₄, ,1%], 1206

[(C₂₆H₂₆O₄)¹₃, ,1%], 804 [(C₂₆H₂₆O₄)¹₂, 4%], 402

(C₂₆H₂₆O¹₄, 100%). IR (KBr): n~ cm²¹2941 (w); 2855 (w);

2161 (w, CuC); 1643 (vs, CvO); 1625 (w, CvC); 1549

(w); 1428 (m); 1406 (w); 1375 (m); 1353 (w); 1326 (w);

1,8-Bis(4-chloro-3,6-dioxocyclohexa-1,4-dienyl)-octa-3,5-

6792

Table 3. Crystal data and structure re®nement for a-3b, b-3b, 3c, 3e and 3f

a-3b b-3b

C₂₆H₃₀O₄

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

3c

3e

3f

Empirical formula

Molecular mass [g mol²¹

Solvent

C₂₆H₃₀O₄

406.5

Methanol

C₂₈H₃₄O₄C₂₄H₂₄F₂O₄

434.6 414.4

n-hexane/benzene (10:1) [D₆]-benzene

C₂₄H₂₄Cl₂O₄

447.3

Toluene

0.5£0.4£0.3

Light yellow

Prism

]

406.5

Ethanol

0.5£0.25£0.05

Colorless

Plate

Crystal size [mm]

Crystal color

Crystal shape

0.3£0.2£0.05

Colorless

Plate

0.4£0.4£0.4

Colorless

Needle

0.4£0.4£0.4

Yellow

Plate

Å

P1

Å

P1

Å

P1

Crystal system

P2₁/c

Cell dimensions

Ê

a [A]

Ê

15.560(2)

7.795(1)

9.323(1)

90

90.73(1)

90

1130.7(2)

1.19

2

436

9.2318(4)

10.7979(4)

11.3607(5)

81.665(2)

81.083(2)

87.657(2)

1106.78(8)

1.22

5.023(1)

4.498(1)

9.665(1)

12.133(2)

102.74(1)

99.11(1)

90.86(1)

507.3(2)

1.4

9.244(2)

10.503(1)

11.443(2)

80.55(1)

82.02(3)

89.31(1)

1085.2(3)

1.37

b [A]

Ê

c [A]

35.63(1)

6.655(2)

90

92.45(2)

90

1190.2(6)

1.21

2

468

a [8]

b [8]

g [8]

Ê ³

V [A ]

D_calcd[10³£kg m²³

]

Z

2

436

108

1

218

2

468

193

F(000)

T [K]

193

0/20, 0/10, 212/12 212/11, 214/14, 214/15

193

208

0/5, 212/12, 215/15 212/12, 213/13, 0/15

hkl range (min/max)

Ê ²¹

0/6, 0/46, 28/8

0.66

0.08

(sin u l²¹

m [mm²¹

)_max[A

]

0.66

0.08

0.67

0.08

0.66

0.1

0.66

0.33

]

No. of re¯ns. Colld.

No. of indep. Re¯ns.

No. of re¯ns. Observed

R_int

2802

2710

1661

0.049

139

,0.01

0.097

0.264

1.19

10411

5393

4018

0.075

391

,0.001

0.051

0.126

1.04

3172

2875

2389

0.022

149

,0.01

0.058

0.184

1.16

2721

2417

1537

0.039

184

,0.01

0.044

0.107

1.07

5467

5209

4278

0.016

359

,0.002

0.041

0.118

1.03

Re®ned parameters

(D s²¹

)

max

R [I . 2s(I)]

R_w2

S (gof) on F²

(Dr)_max/(Dr)_min[e A

Ê ²³

]

0.57/20.41

0.29/20.21

0.31/20.32

0.23/20.24

0.95/20.28

Table 4. Crystal data and structure re®nement for 4f and 5

4f´´´benzene

5

Empirical formula

Molecular mass [g mol²¹

Solvent

Crystal size [mm]

Crystal color

Crystal shape

C₂₀H₁₂Cl₂O₄´´´C₆H₆

387.2

Benzene

0.3£0.2£0.02

Orange

Plate

[C₂₈H₃₄O₄]_n

[434.6]_n

n-hexane / benzene (10:1)

0.4£0.4£0.4

Orange

]

Needle

P2₁/c

Crystal system

C2/c

Cell dimensions

Ê

a [A]

Ê

23.126(4)

9.388(1)

11.023(1)

90

114.62(2)

90

2175.6(5)

1.18

4

792

4.940(1)

35.67(5)

6.733(4)

90

92.52(3)

90

1185(2)

1.22

2

468

b [A]

Ê

c [A]

a [8]

b [8]

g [8]

Ê ³

V [A ]

D_calcd[10³£kg m²³

]

Z

F(000)

T [K]

192

193

hklrange (min/max)

Ê ²¹

0/30, 0/12, 214/13

0.66

0.32

0/6, 0/47, 28/8

0.66

0.08

(sin u l²)_max[A

m [mm²¹

]

No. of re¯ns. Colld.

No. of indep. Re¯ns.

No. of re¯ns. observed

R_int

2688

2627

1237

0.119

146

,0.01

0.12

0.206

1.09

0.54/20.52

3151

2850

1939

0.203

193

,0.004

0.137

0.415

1.97

Re®ned parameters

(Ds²¹

)

max

R [I.2s(I)]

R_w2

S (gof) on F²

(Dr)_max/(Dr)_min[e A

Ê ²³

]

0.76/20.62

H. Irngartinger, M. Skipinski / Tetrahedron 56 (2000) 6781±6794

6793

9. Irngartinger, H.; Skipinski, M. Eur J. Org. Chem. 1999, 917±

922.

1306 (m); 1262 (m); 1216 (w); 1183 (w); 1111 (w); 1072

(m); 1028 (m); 863 (m); 829 (w); 814 (w); 795 (w); 756 (w);

716 (m); 619 (w). Raman (solid): n~ cm²¹2087 (s, CuC);

1466 (m, CvC).

10. Sondheimer, F.; Wolovsky, R.; Ben-Efraim, D. A. J. Am.

Chem. Soc. 1961, 83, 1686±1691.

11. Crystallographic data (excluding structure factors) for the

structures reported in this paper have been deposited with the

Cambridge Crystallographic Data Centre. Copies of the data can

be obtained free of charge on application to CCDC, 12 Union

Road, Cambridge CB2 1EZ, UK [Fax: (internat.) 144-(0)-1223-

336033; e-mail: deposit@ccdc.cam.ac.uk], on quoting the

depository numbers CCDC-134098-134104.

12. Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.;

Orpen, A. G.; Taylor, R. J. Chem. Soc. Perkin Trans. 2 1987,

S1±S19.

Crystal structure determinations

Crystal data of a-3b, b-3b, 3c, 3e, 3f, 4f and 5 are presented

in Tables 3 and 4, respectively. Selected bond distances and

angles are given in Tables 1 and 2. Data collection was

performed on an Enraf-Nonius CAD4 diffractometer for

a-3b,b-3c, 3e, 3f, 4f and 5 or a Nonius-Kappa CCD diffract-

ometer for b-3b (Mo-Ka radiation, graphite monochroma-

tor, v22u scan with u2±288). Differentiation of centric

and acentric space groups with the same systematic extinc-

tions were done by the statistic N(Z)-test.⁴²Intensities were

corrected for absorption effects in the case of 3f (numeri-

cal⁴³) and 4f (semi empirical⁴⁴). The structures were solved

by direct methods (shelxs-97⁴⁵) and re®ned by full-matrix

least-squares methods based on F²(shelxl-97⁴⁵and

shelxl-93,²⁹respectively). All non-hydrogen atoms were

re®ned using anisotropic temperature factors. For a-3b, 3c,

4f and 5 the hydrogen atoms were inserted in calculated

positions. All hydrogen atoms of b-3b, 3e and 3f were

re®ned using isotropic temperature factors. Further details

on the structure determinations are given in Tables 3 and 4,

respectively.¹¹

13. Baughman, R. H. J. Polym. Sci., Polym. Phys. Ed. 1974, 12,

1511.

14. Baughman, R. H.; Yee, K. C. J. Polym. Sci., Macromol. Rev.

1978, 13, 219±219.

15. Baughman, R. H.; Chance, R. R. Ann. Acad. Sci. NY 1978,

313, 705±705.

16. Coates G. W.; Dunn A. R.; Henling L. M.; Dougherty D. A.;

Grubbs R. H. Angew. Chem. 1997, 109, 290±293; Angew. Chem.,

Int. Ed. Engl. 1997, 36, 248±251.

17. Dunitz, J. D.; Robertson, J. M. J. Chem. Soc. 1947, 1145±

1156.

18. Cohen, M. D.; Schmidt, G. M. J. Chem. Soc. 1964, 1996±

2000.

19. Cohen, M. D.; Schmidt, G. M. J.; Sonntag, F. I. J. Chem. Soc.

1964, 2000±2013.

The R-factors of 4f and 5 are relatively large. In the case of

4f disorder effects on the included benzene are responsible

for disturbing the crystalline order. A single crystal of 5

consists of a mixture of only 18% of the polymer 5 and

82% of the monomer 3c. The re®nement was performed

with a combination of both structures with the correspond-

ing occupancy factors.

20. Schmidt, G. M. J. Chem. Soc. 1964, 2014±2021.

21. Kitaigorodskii, A. I. Acta. Crystallogr. 1965, 18, 585±590.

22. Kitaigorodskii, A. I. Molecular Crystals and Molecules,

Academic: New York, 1973.

23. Baughman, R. H.; Chance, R. R. J. Appl. Phys. 1976, 47,

4295±4300.

24. Patel, G. N.; Chance, R. R.; Witt, J. D. J. Chem. Phys. 1979,

70, 4387±4392.

25. Patel, G. N.; Duesler, E. N.; Curtin, D. Y.; Paul, I. C. J. Am.

Chem. Soc. 1980, 102, 461±466.

Acknowledgements

26. Okada, S.; Peng, S.; Spevak, W.; Charych, D. Acc. Chem. Res.

1998, 31, 229±239.

We thank the Deutsche Forschungsgemeinschaft for

®nancial support.

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Synthesis, X-ray structure analysis and topochemical photopolymerization of 2,5-dimethoxyphenyl- and quinone-substituted octa-3,5-diynes

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