Oligoether-Substituted Derivatives of Carbon-Rich 1,4,7,10,13,16-Hexaethynyltribenzo[a, e, i]cyclododeca-5,11,17-triyne (C 36 H 12) and 1,4,9,12-Tetrakis(ethynyl)dibenzo[a, g]cyclododeca-5,7,13,15-tetrayne (C 28 H 8): Potential Precursors to the Circular [6]Phenylene ('Antikekulene') Frame

SYNTHESIS

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7

8

1

4

3

7

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2020, 52, A–N

paper

A

en

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

Oligoether-Substituted Derivatives of Carbon-Rich 1,4,7,10,13,16-

Hexaethynyltribenzo[a,e,i]cyclododeca-5,11,17-triyne (C₃₆H₁₂)

and 1,4,9,12-Tetrakis(ethynyl)dibenzo[a,g]cyclododeca-

5,7,13,15-tetrayne (C₂₈H₈): Potential Precursors to the Circular

[6]Phenylene (‘Antikekulene’) Frame

R

Uwe Dahlmann

R

R_n

K. Peter C. Vollhardt*

0

0-0

0

2-5

8

9

1-

1

3

2

0

R

Department of Chemistry, University of California at Berkeley,

Berkeley, California 94720-1460, USA

kpcv@berkeley.edu

R

R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃or p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

Received: 14.12.2019

Accepted: 07.01.2020

Published online: 28.01.2020

DOI: 10.1055/s-0039-1690050; Art ID: ss-2019-m0681-op

phenylenes constitute a unique class of strained cyclohexa-

trienoid hydrocarbons in which benzene rings are fused to

cyclobutadienes in an alternating manner.⁴In this series,

the elusive circular members are special, because the bond

fixation exerted by the antiaromatic four-membered rings

enforces superdelocalization of the inside and outside 4n 

electronic circuits.^2,3,5Unfortunately, our attempts to effect

the conversion of the sensitive oligoalkyne 2a into the cor-

responding targets led only to decomposition. Introduction

of stabilizing and solubilizing alkyl groups (as in 2b,c) was

helpful in as much as single and, more slowly, double cy-

clization could be accomplished. However, further progress

was arrested, even under high temperature conditions,

eventually leading only to disintegration of materials.^2a,3In

the present report, we describe our attempts to complete

the circular frame of 1 by testing the oligoether bearing

substrates 2d,e in this strategy. During the course of these

investigations, compounds that allowed the construction of

4a,b became available, in turn permitting the examination

of an as yet untested alternative approach to the target de-

rivatives 3a,b by cocyclization of the former with 5a,b (Fig-

ure 1). Oligoether substituents of the type shown have been

used advantageously in synthetic and materials applica-

tions of related systems.^1c–h,6,7In our case, we hoped that

they would address specifically our concerns of robustness

and solubility of the final targets as well as their precursors,

as well as possibly facilitate metal-catalyzed transforma-

tions by ligation. In a more general synthetic vein, these ef-

forts would make available an array of new synthetic build-

ing blocks of potential utility to practitioners in the field.

Abstract The title compounds, in which the terminal alkyne functions

are adorned with -CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃or -p-C₆H₄OCH₂CH₂

OCH₂CH₂OCH₃substituents, were synthesized. The strategies for their

preparation relied on prior art and involved the use of Sonogashira alky-

nylations of appropriate haloarenes, Stephens–Castro cyclizations of

1,2,4-trialkynyl-3-iodobenzenes, and Hay oxidative couplings of

1,2,3,4-tetralkynylbenzenes. The targets form yellow materials, exhibit-

ing yellow-green fluorescence, and they are very soluble in polar sol-

vents, but only sparingly so in nonpolar media. Attempts to convert

them into the antikekulene frame through CpCo(CO)₂-catalyzed (co)-

cyclizations failed.

Key words alkynes, carbon-rich compounds, cyclotrimerizations, de-

hydroannulenes, phenylenes

Dehydrobenzannulenes(‘benzocyclynes’)havegarnered

significant attention, historically because of their ring cur-

rent properties, but more recently because of their poten-

tial applications in material science, such as in optical elec-

tronic devices, nanomaterials, supramolecular constructs,

2D carbon nets, liquid crystals, as monomers in topochemi-

cal and other polymerizations, and more.¹We have report-

ed on the recognition that some such arrays, when suitably

adorned by additional ethynyl substituents, for example 2,

could be related retrosynthetically to the first member of

the circular phenylenes, circular [6]phenylene (‘antikeku-

lene’) ([N] = number of benzene rings) 1, by CpCo(CO)₂-

catalyzed alkyne cyclotrimerization (Figure 1).^2,3The

Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

R

O

R

O

Br

O

Cl₂Pd(PPh₃)₂(0.25 equiv),

CuI (0.25 equiv), Et₃N,

12 h, 70 °C

R

O

Br

R

or

O

+

O

R

2a, R = H

2b, R = Pr

2c, R = CH₂C₆H₁₁

1a, R = H

1b, R = Pr

1c, R = CH₂C₆H₁₁

6a

6b

(2.5 equiv)

(1.1 equiv)

2d, R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

2e, R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

1d, R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

1e, R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

R

Br

R

+

Br

+ 2

R

7d, 61%

7e, 57%

9d, 18%

9e, 10%

10d, 8%

10e, 0%

from 8d,e + 5a,b

8d, 12%

8e, 25%

R

respectively

4a,b

d: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

e: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

5a,b

3a,b

a: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

b: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

Scheme 1 Alkynylation of 1,2,3,4-tetrabromobenzene with 6a and 6b,

respectively, to assemble 7d,e–9d,e; tetraalkynyl derivative 10d is gen-

erated during the alkynylation of 8d with 6a, in addition to 7d and 9d

Figure 1 Retrosynthetic disconnection of the circular [6]phenylene

frames 1 and 3 to the ethynylated benzocyclynes 2 and 4, respectively

separate from 11, and attempts to push conversion of 7d,e

with excess (trimethylsilyl)acetylene and at temperatures

>100 °C only increased the amounts of 12 formed. Similar

problems were encountered in the assembly of 13e and

15d, respectively (Scheme 2). Thus, while switching to (tri-

isopropylsilyl)acetylene (performed for only 7e) served to

reduce the amount of tetralkynyl product formed, conver-

sion of dibromide remained poor (60% recovery). Turning to

2-methylbut-3-yn-2-ol (performed for only 7d) improved

the yield of monoalkynylation (to 15d), but also that of 16d,

with 36% of 7d remaining. Interest in alkyne 15d stemmed

from the hope that it might function as a direct precursor to

2d by in situ deprotection and Pd-catalyzed cyclization, as

reported for a preparation of the parent tribenzo[a,e,i]-

cyclododeca-5,11,17-triyne.¹²

Unsatisfied by this state of affairs, it was thought that a

more selective monoalkynylation might be attained by ex-

changing one of the bromines in 7d,e with iodine. Indeed,

low-temperature lithiation with BuLi, followed by exposure

to I₂resulted in fairly good yields of 17d,e (Scheme 3).¹³

However, again, further Pd-catalyzed coupling with

(trimethylsilyl)acetylene, while proceeding more efficiently

than that of 7d,e (Scheme 2), still gave significant amounts

of doubly coupled derivatives 12d,e (Scheme 3), detracting

from the synthetic utility of the sequence.

The synthesis of 2d,e relied on the respective strategies

executed previously,^2a,3but employing the oligoether

alkynes 6a⁸or 6b⁹(see experimental section and SI) as the

peripheral alkyne substituent synthons. The route to 2d,e

entailed in the first step the Pd-catalyzed 1,4-dialkynyla-

tion of 1,2,3,4-tetrabromobenzene¹⁰to 7d,e (Scheme 1).¹¹

The desired products could be obtained in moderate

yields, comparable to those acquired in the construction of

2b,c,^2ain addition to the under- and overalkynylated sys-

tems 8d,e and 9d,e, respectively. Reexposure of the former

to the reaction conditions allowed for a significant im-

provement of the overall yield of 7 (8d → 7d, 65%; 8e → 7e,

59%; see experimental section). In the case of 8d, this pro-

cess also generated small amounts of the tetrayne 10d.

The next task was the introduction of a single (initially

protected) ethynyl group to 7, completing the composition

of the basic building block that assembles 2 on cyclotri-

merization (Scheme 2). Unfortunately, this step proved to

be cumbersome. For example, treatment of 7d,e with

(trimethylsilyl)acetylene (1.1 equiv) at 100 °C generated the

desired 11d,e in only ~20% yield, in addition to the te-

tralkynyl systems 12d,e and significant amounts of unre-

acted starting dibromide ~70%; see experimental section).

The second alkynylation could not be suppressed under

various reaction conditions, moreover 12 was difficult to

C

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

exception (vide supra) evaporated, when its treatment with

aqueous NaOH and Pd-Cu catalysts under phase-transfer

conditions¹²led to only decomposition. Therefore, as shown

in Scheme 4, 11d,e were subjected to the same sequence

used for the conversion of 7d,e into 17d,e (Scheme 3), pro-

viding the iodoarenes 18d,e, which were then deprotected

to 20d,e. Similarly, 13e from Scheme 2 could be engaged to

augment the supply of 20e via bromine–iodine exchange to

19e (78%), the TIPS analogue of 18e (see experimental sec-

tion), and its protodesilylation employing TBAF (97%). Final-

ly, 20d,e transformed to air stable 2d,e by Stephens–Castro

coupling^2a,15in moderate yields (Scheme 4). Their D_3hsym-

metry is evident in their relatively simple NMR spectra. Like

their relatives 2a–c, they are yellow materials (2d: oil; 3e:

solid), exhibiting intense yellow-green fluorescence (for the

fluorescence data, see experimental section).¹⁶As expected,

these macrocycles (as well as all of the precursors in their

synthesis) are very soluble in polar solvents and only spar-

ingly so in nonpolar media. One notes that this and prior

steps do not seem the benefit from the presence of the po-

tentially chelating oligoether appendages when compared

to those featured in the routes to 2a–c.^2a

R

TMSC CH

(1.1 equiv),

Cl₂Pd(PPh₃)₂

(0.13 equiv), CuI

(0.13 equiv), Et₃N,

12 h, 100 °C

≡

TMS

Br

+

Br

R

7d,e

11d, 19%

11e, 21%

12d, 10%

12e, 3%

R

TIPSC CH

≡

(1.1 equiv),

Cl₂Pd(PPh₃)₂

(0.13 equiv), CuI

(0.13 equiv), Et₃N,

12 h, 100 °C

TIPS

7e

+

Br

R

13e, 28%

14e, 1%

HOC(CH ) C CH

≡

3

2

(1.5 equiv),

Cl₂Pd(PPh₃)₂(0.07

equiv), CuI (0.07

equiv), Et₃N, 24 h,

100 °C

OH

+

OH

1. BuLi (1.2 equiv),

THF, −110 °C, 1 h

2. I₂(1.5 equiv),

R

7d

Br

TMS

K₂CO₃,

MeOH,

TMS THF, −110 °C,

30 min, then warm

to r.t.

OH

30 min, r.t.

R

I

Br

15d, 36%

16d, 9%

d: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

e: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

R

18d, 47%

18e, 80%

11d,e

Scheme 2 Various monoalkynylations of 7d,e

R

1. BuLi (1.2 equiv),

Et₂O, −110 °C, 1 h

2. I₂(1.5 equiv),

Et₂O, −110 °C,

30 min, then warm

to r.t.

R

1. CuCl, NH₄OH,

EtOH [EtOH/DMSO

(1:2) for 20e], 1 h, r.t.

2. pyr, 6 h, Δ

TMSC CH

(1.5 equiv),

Cl₂Pd(PPh₃)₂

(0.15 equiv), CuI

(0.15 equiv), Et₃N,

8 h, 60 °C

≡

2d, 24%

2e, 23%

Br

I

Br

11d,e, 40−60%

+

12d,e, 20−30%

I

R

7d,e

20d, 99%

20e, 96%

17d, 64%

17e, 85%

d: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

e: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

d: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

e: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

Scheme 4 Preparation of targets 2d,e through bromine–iodine ex-

change of 11d,e to give 18d,e, subsequent deprotection, and cycliza-

tion

Scheme 3 Bromine–iodine exchange of 7d,e to give 17d,e and subse-

quent (trimethylsilyl)ethynylation to 11d,e and 12d,e

The availability of the tetraalkynylarenes 12d,e and 14e

(albeit as side products of the synthesis of 11d,e and 13e,

respectively; Scheme 2) suggested a ready test of the viabil-

ity of the retrosynthetic analysis 3 ⇒ 4 (Figure 1), as their

deprotected versions should lead to the required benzo-

cyclyne 4 by oxidative dimerization.^14bConsequently,

Nevertheless, with sufficient quantities of materials in

hand, the next step was to convert the bromine substituent

in 11d,e (and 13e) into iodine, necessary because the bro-

mides appear to be unsuitable for the eventual cyclization

to 2d,e.¹⁴The hope that alcohol 15d would prove to be an

D

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

improved preparations of these materials were developed

(Scheme 5), applying excess silylalkyne for the couplings

with dibromides 7d,e and furnishing good quantities of 12d

(82%), 12e (78%), and 14e (57%; see experimental section).

Desilylation of all proceeded nearly quantitatively on treat-

ment with basic MeOH (Scheme 5) or TBAF (for 14e, see ex-

perimental section) to supply 21d,e. The latter were then

transformed into tetraynes 4a,b under Hay conditions,^16k,l,17

generating minor amounts of the only partly characterized

cyclic trimers 22d,e.^2cCompounds 4a,b exist as sensitive,

shiny yellow, fluorescent crystalline materials, very soluble

in polar solvents and decomposing on melting.

ingly, the outcome of its exposure to excess CpCo(CO)₂

mimicked those observed previously with 2b and c.^2aThus

(Scheme 6), the first cycloisomerization took place quite

well in boiling m-xylene (bp 139 °C) to provide the angular

[3]phenylene frame of 23 in 60% yield. The second step to

24 needed the much higher temperature of boiling

tetraglyme (bp 275 °C) to proceed, but attempted further

conversion into 1e reached an impasse from which the only

escape was gradual decomposition on prolonged heating.

The spectral data of 23 and 24 compare well with those of

their propyl and cyclohexylmethyl analogues,^2ain turn rest-

ing on the presence of highly diagnostic NMR and UV/Vis

absorptions for the phenylene substructures.^4,18These find-

ings cement the original structural rationale for the failure

to effect the conversion of 2 into 1: The introduction of

phenylene units causes the remaining triple bonds to be in-

creasingly distant, posing an insurmountable barrier for the

final cyclization.

R

TMSC CH

(6 equiv),

≡

Cl₂Pd(PPh₃)₂

TMS

K₂CO₃(4 equiv),

H₂O, MeOH,

30 min, r.t.

(0.05 equiv), CuI

(0.05 equiv), Et₃N,

12 h, 100 °C

7d,e

TMS

R

CpCo(CO)₂

(3.3 equiv),

m-xylene, Δ,

hυ, 25 min

CpCo(CO)₂

(7.1 equiv),

tetraglyme,

Δ, hυ, 25 min

R

12d, 82%

12e, 78%

2e

R

CuCl (1.2 equiv)

PhCl, TMEDA,O₂

1.25 h, r.t.

R

+

23, 60%

R

21d, 98%

21e, 92%

4a, R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃, 39%

4b, R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃, 24%

1e

Χ

R

24, 21%

R

Scheme 6 Attempted CpCo-catalyzed cycloisomerization of 2e to 1e

via 23 and 24

In view of this fiasco, further efforts along this strategy

involving 2d were abandoned, and our attention turned to

the potential of the 4 + 5 → 3 approach (Figure 1), focusing

first on the reaction of 4a with 5a (10 equivalents) in the

presence of CpCo(CO)₂(5 equivalents) in boiling m-xylene.

Lamentably, this treatment led to extensive decomposition,

without the generation of any identifiable material. To test

the basic reactivity of 4a in cocyclizations, the reaction was

repeated with bis(trimethylsilyl)acetylene (BTMSA) in m-

xylene (1:1). A complex mixture of CpCo complexes ensued,

parceled into various fractions by repeated column chroma-

tography and containing in part the known products de-

rived from the reaction of BTMSA with CpCo(CO)₂(¹H

NMR), most prominently CpCo[1,2,3,4-tetrakis(trimethyl-

R

22d, 4%

22e, <1.4%

d: R = CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₃

e: R = p-C₆H₄OCH₂CH₂OCH₂CH₂OCH₃

Scheme 5 Synthesis of benzocyclynes 4a,b and 22d,e starting from di-

bromides 7d,e

Having accessed the benzocyclynes in Figure 1, our at-

tention turned to their CpCo-catalyzed (co)cyclizations. We

chose 2e as a first substrate, in which the phenylether sub-

stituents were expected to impart crystallinity. Disappoint-

E

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

silyl)cyclobutadiene] (18% based on CpCo(CO)₂).¹⁹In addi-

tion, one fraction indicated the formation of a mixture of

(mainly two) cyclobutadiene complexes derived from 4a

and BTMSA, as evidenced by sets of four doublets (J ≈ 8 Hz)

for the desymmetrized benzocyclyne frame and the corre-

sponding CpCo and TMS singlets. Most telling was the ab-

CH₂Cl₂(3 × 100 mL), and the organic layers were combined, washed

with H₂O (3 × 100 mL), and dried (MgSO₄). Evaporation of the sol-

vents under reduced pressure and vacuum distillation of the residual

liquid gave 6a as a colorless liquid; yield: 12.9 g (75%); bp 47–

48 °C/0.1 Torr. Employment of prop-2-yn-1-yl 4-methylbenzenesul-

fonate in DME instead of 3-bromoprop-1-yne generated 6a in only

40% yield.

1

sence of any relatively shielded H NMR absorptions that

IR (film): 3251, 2975, 2868, 2114, 1444, 1349, 1289, 1246, 1107,

1033, 948, 920, 844, 671 cm^–1

.

would be have been expected for the angular [3]phenylene

substructure. Consequently, this line of enquiry was termi-

nated.

¹H NMR (300 MHz, CDCl₃):  = 4.19 (d, J = 2.4 Hz, 2 H), 3.68 (AA′BB′m,

4 H), 3.64 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.51 (q, J = 7.0 Hz, 2 H), 2.40

(t, J = 2.4 Hz, 1 H), 1.19 (t, J = 7.0 Hz, 3 H).

¹³C NMR (100 MHz, CDCl₃):  = 79.3 (CH), 74.3 (C_quat), 70.4 (CH₂), 70.1

(CH₂), 69.5 (CH₂), 68.8 (CH₂), 66.3 (CH₂), 58.0 (CH₂), 14.8 (CH₃).

MS (EI, 70 eV): m/z (%) = 173 ([MH⁺], 55), 127 (10), 117 (10), 103 (20),

83 (40), 73 (100), 59 (70).

HRMS (EI, 70 eV): m/z [MH⁺] calcd for C₉H₁₇O₃: 173.1178; found:

173.1173.

In conclusion, we have made available new alkyne syn-

thetic building blocks containing oligoether substituents of

potential use to researchers engaged in the exploration of

supramolecular assemblies. In our efforts, these were elab-

orated to the benzocyclynes 2d, 2e, 4a, and 4b, with the aim

to test their suitability as precursors to the antikekulenes

1d, 1e, 3a, and 3b. The substituents delivered on their

promise to impart excellent solubility on these compounds,

but did not do so with respect to improving the efficiency

of the various Pd-, Cu-, and Co-mediated transformations.

In particular, the specific aim to exploit them for the assem-

bly of the antikekulene nucleus failed.

1-Ethynyl-4-[2-(2-methoxyethoxy)ethoxy]benzene (6b)⁹

To a suspension of pure NaH (1.20 g, 50 mmol) in anhyd DME

(100 mL) was added slowly a solution of 4-iodophenol (11.0 g, 50

mmol) in anhyd DME (50 mL) at r.t. to give a clear solution after stir-

ring for 30 min. This mixture was treated with 1-bromo-2-(2-me-

thoxyethoxy)ethane (6.80 mL, 9.25 g, 50 mmol) in one portion with

vigorous stirring, followed by boiling for 3 h, cooling to r.t., filtration,

solvent evaporation under reduced pressure, and vacuum distillation

to render 1-iodo-4-[2-(2-methoxyethoxy)ethoxy]benzene as a light-

sensitive, colorless, glass-like solid; yield: 12.8 g (79%); mp 35–45 °C;

bp 133–135 °C/0.25 Torr. The product can also be purified by column

chromatography (silica gel, EtOAc/hexane 1:1).

All reactions were carried out in degassed solvents under N₂in flame-

dried glassware. Unless otherwise noted, starting materials were ob-

tained commercially and the solvents purified and dried applying

common methods.²⁰Et₃N, TMEDA, and pyridine were freshly distilled

from KOH. Et₂O, DME, THF, and m-xylene were distilled from sodium

benzophenone ketyl just prior to use. Chlorobenzene was dried by

boiling over CaH₂. Silica gel (60–200 mesh) for column chromatogra-

phy was purchased from ICN-Biomedicals. TLC was performed on

Merck silica gel 60 F₂₅₄(aluminum foil). Mps were determined in

open Pyrex capillaries on a Thomas Hoover melting point apparatus

and are uncorrected. GC was carried out on a Hewlett Packard HP

5890 Series II instrument. UV-Visible spectra were recorded with

CH₃CN solutions on a Hewlett Packard HP 8453 UV-Vis ChemStation.

Fluorescence spectra were measured with MeCN solutions on an

ISA/SPEX Fluorolog 3.22 spectrometer equipped with a 450-W Xe

lamp. The samples were excited at the described wavelength, slit

widths were set to 2 nm bandpass (excitation) and 3 nm bandpass

(emission). IR spectra were obtained on films (NaCl) or KBr pellets

with a Perkin-Elmer PE 2000 FT-IR spectral photometer. ¹H NMR and

¹³C{H} spectra were recorded on Bruker DRX-500, AMX-400, AM-400,

and AMX-300 spectrometers. When so specified, the extent of substi-

tution on carbon was determined by APT (attached proton test) spec-

tra. Mass data were provided by the UC Berkeley Mass Laboratory or

were measured as GC-MS spectra on a Hewlett Packard HP 5970A

mass detector instrument at 70 eV combined with the GC apparatus

described above.

IR (film): 2924, 2877, 2824, 1587, 1486, 1454, 1401, 1355, 1331,

1283, 1246, 1200, 1176, 1111, 1058, 1030, 1000, 940, 924, 822, 695,

636, 585 cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.53 (d, J = 9.0 Hz, 2 H), 6.69 (d, J = 9.0

Hz, 2 H), 4.09 (AA′m, 2 H), 3.84 (BB′m, 2 H), 3.70 (AA′m, 2 H), 3.57

(BB′m, 2 H), 3.38 (s, 3 H).

¹³C NMR (125 MHz, CDCl₃):  = 158.6 (C_quat), 138.1 (CH), 117.0 (CH),

82.9 (C_quat), 71.9 (CH₂), 70.7 (CH₂), 69.6 (CH₂), 67.5 (CH₂), 59.1 (CH₃).

MS (EI, 70 eV): m/z (%) = 322 ([M⁺], 100), 246 (10), 220 (20), 203 (55),

150 (5), 120 (15), 103 (40), 76 (15), 59 (85).

At r.t., a solution of (trimethylsilyl)acetylene (6.40 mL, 4.42 g, 45

mmol,) in Et₃N (20 mL) was injected into a Fisher–Porter vessel con-

taining 1-iodo-4-[2-(2-methoxyethoxy)ethoxy]benzene (11.9 g,

37 mmol), Cl₂Pd(PPh₃)₂(702 mg, 1.00 mmol), and CuI (190 mg,

1.00 mmol) in Et₃N (130 mL). The bottle was sealed and the mixture

stirred for 24 h at r.t., followed by 2 h at 50 °C. During this time, the

solution turned bright yellow rapidly, then yellow-brown, and finally

dark brown with the formation of a precipitate. After filtration, the

solvent was evaporated in vacuo and the resulting residue purified by

column chromatography (silica gel, hexane/EtOAc 2:1) to furnish 1-

[2-(2-methoxyethoxy)ethoxy]-4-[(trimethylsilyl)ethynyl]benzene as

a colorless oil; yield: 10.44 g (96%).

3-[2-(2-Ethoxyethoxy)ethoxy]prop-1-yne (6a)⁸

To a suspension of pure NaH (2.40 g, 100 mmol) in anhyd DME

(100 mL) was slowly added 2-(2-ethoxyethoxy)ethanol (13.42 g,

100 mmol) at r.t. After stirring for 30 min, the now clear solution was

treated with 3-bromoprop-1-yne (11.9 g, 100 mmol) in PhMe (2 mL)

over a period of 15 min (violent reaction) with vigorous stirring. The

resulting blend was heated to reflux for 4 h, allowed to cool to r.t., and

filtered. Addition of H₂O (300 mL) was followed by extraction with

IR (film): 3043, 2958, 2927, 2879, 2822, 2156, 1605, 1570, 1507,

1455, 1411, 1356, 1331, 1288, 1250, 1200, 1173, 1111, 1062, 925,

866, 842, 761, 699, 638, 542 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.39 (d, J = 8.8 Hz, 2 H), 6.83 (d, J = 8.8

Hz, 2 H), 4.14 (AA′m, 2 H), 3.86 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.58

(BB′m, 2 H), 3.40 (s, 3 H), 0.23 (s, 9 H).

F

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

¹³C NMR (100 MHz, CDCl₃):  = 158.6 (C_quat), 133.0 (CH), 115.0 (C_quat),

114.1 (CH), 104.9 (C_quat), 92.0 (C_quat), 71.5 (CH₂), 70.3 (CH₂), 69.2 (CH₂),

67.0 (CH₂), 58.6 (CH₃), –0.27 (CH₃).

¹H NMR (300 MHz, CDCl₃):  = 7.33 (s, 2 H), 4.48 (s, 4 H), 3.79 (AA′ m,

4 H), 3.71 (BB′m, 4 H), 3.66 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.51 (q,

J = 7.0 Hz, 4 H), 1.20 (t, J = 7.0 Hz, 6 H).

MS (EI, 70 eV): m/z (%) = 292 ([M⁺], 100), 233 (5), 175 (40), 103 (30),

¹³C NMR (100 MHz, CDCl₃):  = 131.2, 128.4, 126.5, 92.0, 84.8, 70.5,

89 (10), 73 (5), 59 (55).

70.3, 69.6, 69.1, 66.4, 58.9, 15.0.

To

a

solution of 1-[2-(2-methoxyethoxy)ethoxy]-4-[(trimethylsi-

MS (EI, 70 eV): m/z (%) = 576 ([M⁺], 2), 503 (10), 442 (19), 327 (15),

311 (26), 217 (20), 150 (28), 117 (50), 103 (75), 89 (58), 73 (100), 59

(40).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₂₄H₃₂⁷⁹Br₂O₆: 574.0566; found:

574.0567.

lyl)ethynyl]benzene (10.2 g, 35 mmol) in MeOH (200 mL) was added

sat. aq K₂CO₃(5 mL, 40 mmol) at r.t. The resulting cloudy solution was

stirred until clear (approx. 1 h, TLC monitoring), diluted with CH₂Cl₂

(200 mL), washed with H₂O (3 × 100 mL), dried (MgSO₄), and the vola-

tiles were removed under reduced pressure. The crude material was

purified by column chromatography (silica gel, hexane/EtOAc 2:1) to

supply 6b as a colorless oil; yield: 7.15 g (93%).

UV/VIS (MeCN): _max(log ) = 222 (4.34), 229 (4.35), 277 (4.39), 289

nm (4.51).

The last fraction gave rise to trialkynylated ingredient 2-bromo-1,3,4-

tris{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (9d) as a

yellow oil; yield: 1.20 g (18%).

IR (film): 3285, 3072, 3042, 2926, 2879, 2824, 2106, 1606, 1571,

1505, 1455, 1355, 1289, 1249, 1200, 1172, 1110, 1061, 1030, 925,

835, 702, 659, 642 cm^–1

.

IR (film): 2974, 2868, 2228, 1578, 1486, 1458, 1385, 1349, 1292,

¹H NMR (400 MHz, CDCl₃):  = 7.41 (d, J = 8.8 Hz, 2 H), 6.85 (d, J = 8.8

Hz, 2 H), 4.14 (AA′m, 2 H), 3.86 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.57

(BB′m, 2 H), 3.39 (s, 3 H), 2.99 (s, 1 H).

¹³C NMR (100 MHz, CDCl₃):  = 158.8 (C_quat), 133.1 (CH), 114.2 (CH),

113.9 (C_quat), 83.3 (C_quat), 75.8 (CH), 71.5 (CH₂), 70.3 (CH₂), 69.2 (CH₂),

67.0 (CH₂), 58.6 (CH₃).

1267, 1246, 1209, 1099, 1056, 1030, 977, 947, 843, 763, 669 cm^–1

.

¹H NMR (300 MHz, CDCl₃):  = 7.31 (s, 2 H), 4.50 (s, 2 H), 4.47 (s, 2 H),

4.45 (s, 2 H), 3.85–3.75 (m, 6 H), 3.72–3.69 (m, 6 H), 3.67–3.63 (m,

6 H), 3.61–3.56 (m, 6 H), 3.52 (q, J = 7.0 Hz, 2 H), 3.51 (q, J = 7.0 Hz,

4 H), 1.19 (t, J = 7.0 Hz, 9 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 131.8, 130.2, 128.3,

127.6, 126.4, 125.3, 94.3, 91.6, 91.4, 84.3, 84.0, 83.5, 70.5 (3 C), 70.2 (3

C), 69.6 (3 C), 69.1, 69.0, 68.9, 66.4 (3 C), 58.8 (br, 3 C), 14.9 (3 C).

MS (FAB, 70 eV): m/z (%) = 221 ([MH⁺]).

HRMS (FAB, 70 eV): m/z [M⁺] calcd for C₁₃H₁₆O₃: 221.1099; found:

221.1103.

MS (EI, 70 eV): m/z (%) = 534 ([M⁺], 4), 532 ([M⁺], 4), 461 (1), 459 (1),

117 (20), 73 (55), 59 (100).

MS (FAB, 70 eV): m/z (%) = 669 ([MH⁺]), 667 ([MH⁺]).

2,3-Dibromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-

yl}benzene (7d)

Alkyne 6a (4.30 g, 25 mmol) in Et₃N (50 mL) was injected into a

Fisher–Porter vessel containing a mixture of 1,2,3,4-tetrabromoben-

zene¹⁰(3.94 g, 10 mmol), Cl₂Pd(PPh₃)₂(176 mg, 0.25 mmol), and CuI

(48 mg, 0.25 mmol) in Et₃N (100 mL) at r.t. The mixture was stirred

for 12 h at 70 °C, during which it turned rapidly bright yellow, then

yellow-brown, and finally dark brown with the formation of a precip-

itate. The suspension was cooled to r.t., filtered, and the volatiles re-

moved in vacuo. The resulting residue was purified by column chro-

matography (silica gel, Et₂O) to separate first the monoalkynylated

constituent 1,2,3-tribromo-4-{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-

yn-1-yl}benzene (8d) as a light yellow oil; yield: 600 mg (12%).

HRMS (FAB, 70 eV): m/z [MH⁺] calcd for C₃₃H₄₈⁸¹BrO₉: 669.2461);

found: 669.2457.

UV/VIS (MeCN): _max(log ) = 247 (4.60), 254 (4.67), 277 (4.33), 283

(4.36), 294 nm (4.49).

2,3-Dibromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-

yl}benzene (7d) by Alkynylation of 8d

Monoalkynylated 8d (4.85 g, 10 mmol) was exposed to 6a (3.80 g, 22

mmol) as in the preceding preparation of 7d, except that the reaction

temperature was kept at 100 °C, to engender, in order of elution on

chromatography, 7d; yield: 4.37 g (65%); 9d; yield: 1.27 g (19%); and

the tetraalkynylated product 1,2,3,4-tetrakis{3-[2-(2-ethoxye-

thoxy)ethoxy]prop-1-yn-1-yl}benzene (10d) as a yellow oil; yield:

610 mg (8%).

IR (film): 3073, 2973, 2867, 2224, 1563, 1485, 1456, 1430, 1374,

1340, 1287, 1271, 1242, 1103, 1054, 1031, 976, 946, 817, 787, 722

cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.50 (d, J = 8.3 Hz, 1 H), 7.24 (d, J = 8.3

Hz, 1 H), 4.45 (s, 2 H), 3.79 (AA′M, 2 H), 3.70 (BB′m, 2 H), 3.64 (AA′m, 2

H), 3.58 (BB′m, 2 H), 3.51 (q, J = 7.0 Hz, 2 H), 1.19 (t, J = 7.0 Hz, 3 H).

¹³C NMR (100 MHz, CDCl₃):  = 132.1, 131.7, 129.1, 128.2, 125.9,

125.8, 91.3, 84.5, 70.6, 70.3, 69.7, 69.2, 66.5, 58.9, 15.1.

MS (EI, 70 eV): m/z (%) = 486 ([M⁺], 2), 484 ([M⁺], 2), 456 (2), 454 (2),

440 (2), 438 (2), 427 (10), 425 (10), 413 (2), 411 (2), 353 (57), 351

(57), 274 (18), 272 (18), 193 (20), 191 (20), 116 (17), 73 (64), 72 (100),

59 (40).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₁₅H₁₇⁷⁹Br₃O₃: 481.8728; found:

481.8728.

IR (film): 2974, 2868, 2227, 1486, 1462, 1408, 1349, 1297, 1245,

1106, 1049, 1029, 947, 845 cm^–1

.

¹H NMR (300 MHz, CDCl₃):  = 7.30 (s, 2 H), 4.48 (s, 4 H), 4.44 (s, 4 H),

3.81–3.75 (m, 8 H), 3.69–3.62 (m, 16 H), 3.61–3.57 (m, 8 H), 3.51 (q,

J = 7.1 Hz, 4 H), 3.50 (q, J = 7.1 Hz, 4 H), 1.191 (t, J = 7.1 Hz, 6 H), 1.187

(t, J = 7.1 Hz, 6 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 131.1, 127.7, 125.3,

93.5, 90.9, 84.1, 83.2, 70.54, 70.53, 70.3 (2 C), 69.6 (2 C), 69.0, 68.8,

66.4 (2 C), 58.92, 58.89, 15.0 (2 C).

MS (EI, 70 eV): m/z (%) = 758 ([M⁺], 0.2), 624 (3), 552 (25), 117 (45),

UV/VIS (MeCN): _max(log ) = 224 (4.55), 257 (4.28), 269 nm (4.24).

103 (20), 73 (75), 59 (100).

A second fraction furnished dialkynylated product 7d as a light yellow

UV/VIS (MeCN): _max(log ) = 254 (sh, 4.60), 256 (sh, 4.65), 263 (4.77),

oil; yield: 3.50 g (61%).

277 (4.47), 285 (4.28), 296 nm (4.47).

IR (film): 2974, 2868, 2220, 1577, 1485, 1449, 1375, 1351, 1289,

1245, 1107, 1032, 971, 945, 841, 733, 666 cm^–1

.

G

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

2,3-Dibromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)benzene (7e)

UV/VIS (MeCN): _max(log ) = 228 (4.51), 234 (sh, 4.50), 286 (sh, 4.48),

322 (4.79), 343 (sh, 4.66), 361 nm (sh, 4.61).

Following the procedure employed for the preparation of 7d, treat-

ment of 1,2,3,4-tetrabromobenzene¹⁰(3.94 g, 10 mmol) with alkyne

6b (4.88 g, 22 mmol) and column chromatography (silica gel, EtOAc)

produced a first fraction containing 1,2,3-tribromo-4-({4-[2-(2-me-

thoxyethoxy)ethoxy]phenyl}ethynyl)benzene (8e) as colorless crys-

tals; yield: 1.35 g (25%); mp 84 °C (EtOH).

Compound 7e could also be made by alkynylation of 8e following the

protocol used for the conversion of 8d to give 7d, 9d, and 10d (vide

supra) to afford 7e (59%) and 9e (21%), but no 10e.

2-Bromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-

[(trimethylsilyl)ethynyl]benzene (11d)

IR (KBr): 2985, 2951, 2925, 2889, 2856, 2816, 2224, 1605, 1561, 1509,

1456, 1429, 1384, 1363, 1340, 1283, 1250, 1167, 1140, 1114, 1085,

(Trimethylsilyl)acetylene (0.75 mL, 520 mg, 5.30 mmol) in Et₃N

(10 mL) was injected into a Fisher–Porter vessel containing 7d (2.88 g,

5.00 mmol), Cl₂Pd(PPh₃)₂(176 mg, 0.25 mmol), and CuI (48 mg,

0.25 mmol) in Et₃N (100 mL) at r.t. The vessel was sealed and the mix-

ture heated at 100 °C for 12 h. Column chromatography (silica gel,

Et₂O), supplied a first fraction containing 1,4-bis{3-[2-(2-ethoxy-

ethoxy)ethoxy]prop-1-yn-1-yl}-2,3-bis[(trimethylsilyl)ethynyl]ben-

zene (12d) as a yellow oil; yield: 300 mg (10%).

1058, 1021, 936, 916, 848, 823, 724, 562, 532 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.54 (d, J = 8.4 Hz, 1 H), 7.49 (d, J = 8.8

Hz, 2 H), 7.32 (d, J = 8.4 Hz, 1 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.17 (AA′m, 2

H), 3.87 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.40 (s, 3 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.4, 133.2, 131.8, 131.6, 128.9,

128.2, 126.9, 125.1, 114.7, 114.5, 95.5, 86.9, 71.9, 70.7, 69.6, 67.4,

59.0.

MS (EI, 70 eV): m/z (%) = 534 ([M⁺], 65), 532 ([M⁺], 65), 432 (16), 430

(16), 243 (6), 241 (6), 174 (8), 103 (30), 59 (100).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₁₉H₁₇⁸¹Br₃O₃: 535.8667; found:

535.8667.

IR (film): 2960, 2868, 2157, 1486, 1460, 1394, 1376, 1349, 1287,

1250, 1178, 1101, 1034, 885, 842, 761, 713, 699, 626 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.28 (s, 2 H), 4.46 (s, 4 H), 3.78 (AA′m,

4 H), 3.70 (BB′m, 4 H), 3.65 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.51 (q,

J = 7.0 Hz, 4 H), 1.19 (t, ³J = 7.0 Hz, 6 H), 0.25 (s, 18 H).

¹³C NMR (100 MHz, CDCl₃):  = 131.0, 128.4, 125.5, 103.6, 101.2, 90.8,

84.2, 70.6, 70.4, 69.7, 69.1, 66.5, 59.0, 15.1, –0.14.

MS (EI, 70 eV): m/z (%) = 610 ([M⁺], 5), 537 (10), 493 (20), 476 (40),

147 (8), 117 (40), 103 (8), 73 (100), 59 (15).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₃₄H₅₀O₆Si₂: 610.3146; found:

610.3160.

UV/VIS (MeCN): _max(log ) = 218 (4.32), 244 (4.00), 254 (3.93), 272

(3.89), 309 (4.37), 324 nm (4.38).

The second fraction consisted of 7e as colorless flakes; yield: 3.86 g

(57%); mp 96–97 °C (EtOH).

IR (KBr): 3070, 3041, 2988, 2875, 2824, 2226, 2212, 1602, 1571, 1542,

1516, 1473, 1458, 1383, 1351, 1332, 1303, 1286, 1251, 1197, 1167,

1145, 1123, 1101, 1062, 1030, 955, 925, 911, 885, 855, 844, 828, 811,

UV/VIS (MeCN): _max(log ) = 257 (sh, 4.48), 262 (sh, 4.73), 269 (4.90),

282 (4.64), 287 (sh, 4.55), 298 nm (4.46).

789, 708, 644, 627, 537 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.50 (d, J = 8.9 Hz, 4 H), 7.42 (s, 2 H),

6.91 (d, J = 8.9 Hz, 4 H), 4.17 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.73 (AA′m,

4 H), 3.58 (BB′m, 4 H), 3.40 (s, 6 H).

The second fraction delivered 11d as a yellow oil; yield: 560 mg (19%).

IR (film): 2973, 2867, 2223, 2158, 1577, 1486, 1456, 1377, 1349,

1290, 1250, 1192, 1109, 1035, 977, 945, 883, 847, 760, 701, 684, 663,

624 cm^–1

.

¹³C NMR (100 MHz, CDCl₃):  = 159.2, 133.1, 130.6, 128.1, 126.7,

¹H NMR (400 MHz, CDCl₃):  = 7.30 (ABq, 2 H), 4.45 (s, 4 H), 3.77 (m,

4 H), 3.71 (m, 4 H), 3.65 (m, 4 H), 3.59 (m, 4 H), 3.53 (q, J = 7.0 Hz, 2

H), 3.51 (q, J = 7.0 Hz, 2 H), 1.195 (t, J = 7.0 Hz, 3 H), 1.191 (t, J = 7.0 Hz,

3 H), 0.26 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 31.9, 130.3, 128.6,

128.2, 126.7, 125.4, 104.7, 101.4, 91.6, 91.5, 84.6, 84.1, 70.65, 70.62,

70.4 (2 C), 69.7 (2 C), 69.2 (2 C), 66.6 (2 C), 59.01, 58.98, 15.1, –0.26.

MS (EI, 70 eV): m/z (%) = 594 ([M⁺], 2), 592 ([M⁺], 2), 535 (2), 533 (2),

521 (5), 519 (5), 491 (2), 489 (2), 477 (15), 475 (15), 460 (20), 458

(20), 117 (60), 73 (100), 59 (25).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₂₉H₄₁⁷⁹BrO₆Si: 592.1856; found:

592.1851.

114.6, 114.5, 96.0, 87.4, 71.7, 70.6, 69.4, 67.3, 58.9.

MS (EI, 70 eV): m/z (%) = 672 ([M⁺], 100), 569 (5), 103 (15), 59 (60).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₃₂H₃₂⁷⁹Br⁸¹BrO₆: 672.0545;

found: 672.0543.

UV/VIS (MeCN): _max(log ) = 215 (sh, 4.61), 239 (4.50), 248 (4.49),

345 (4.82), 361 nm (sh, 4.76).

A third fraction was comprised of 3-bromo-1,2,4-tris({4-[2-(2-me-

thoxyethoxy)ethoxy]phenyl}ethynyl)benzene (9e) as light yellow

waxy crystals; yield: 820 mg (10%); mp 40–50 °C (EtOH).

IR (KBr): 2928, 2877, 2824, 2215, 1604, 1571, 1514, 1456, 1357, 1287,

1250, 1200, 1166, 1111, 1059, 924, 829, 647, 612, 535 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.54 (d, J = 9.2 Hz, 2 H), 7.51 (d, J = 9.2

Hz, 2 H), 7.47 (d, J = 9.2 Hz, 2 H), 7.42 (ABq, J = 8.2 Hz, 2 H), 6.905 (d,

J = 8.8 Hz, 2 H), 6.897 (d, J = 8.8 Hz, 2 H), 6.885 (d, J = 9.2 Hz, 2 H), 4.16

(m, 6 H), 3.87 (m, 6 H), 3.73 (m, 6 H), 3.58 (m, 6 H), 3.395 (s, 3 H),

3.393 (s, 6 H).

UV/VIS (MeCN): _max(log ) = 241 (sh, 4.42), 246 (sh, 4.56), 250 (4.59),

258 (4.77), 279 (4.32), 286 (4.35), 296 nm (4.44).

A third fraction returned starting material 7d; yield: 1.50 g (66%).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.22, 159.19, 159.15,

133.13, 133.12, 133.08, 130.9, 129.7, 128.3, 127.8, 126.4, 125.6, 115.1,

115.0, 114.8, 114.63, 114.61 (2 C), 98.4, 95.8, 95.6, 87.2, 86.9, 86.5,

71.8 (3 C), 70.6 (3 C), 69.5 (3 C), 67.4 (3 C), 59.0 (3 C).

3-Bromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)-2-[(trimethylsilyl)ethynyl]benzene (11e)

The procedure for the preparation of 11d was replicated, but starting

with 7e (3.36 g, 5 mmol). Column chromatography (silica gel, Et₂O)

furnished

a first fraction containing 1,4-bis({4-[2-(2-methoxy-

MS (EI, 70 eV): m/z (%) = 812 ([M⁺], 10), 810 ([M⁺], 10), 594 (30), 592

(30), 277 (50), 107 (30), 95 (75), 59 (100).

H

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

ethoxy)ethoxy]phenyl}ethynyl)-2,3-bis[(trimethylsilyl)ethynyl]ben-

zene (12e) as light yellow needles; yield: 100 mg (3%); mp 100–

101 °C dec (MeOH).

MS (FAB, 70 eV): m/z (%) = 875 ([MH⁺]).

UV/VIS (MeCN): _max(log ) = 266 (sh, 4.60), 275 (4.68), 290 (4.71),

345 nm (4.59).

IR (KBr): 2959, 2874, 2826, 2210, 1602, 1510, 1458, 1392, 1355, 1283,

1250, 1198, 1166, 1144, 1123, 1110, 1059, 1030, 1013, 954, 940, 922,

Next to be eluted was 13e, forming colorless crystals; yield: 1.07 g

(28%); mp 108 °C dec (EtOH).

846, 811, 762, 677, 618, 541 cm^–1

.

IR (KBr): 3061, 2941, 2865, 2220, 1602, 1510, 1455, 1378, 1357, 1287,

1246, 1233, 1203, 1170, 1140, 1111, 1060, 1018, 970, 950, 922, 882,

¹H NMR (400 MHz, CDCl₃):  = 7.47 (d, J = 8.8 Hz, 4 H), 7.37 (s, 2 H),

6.89 (d, J = 8.8 Hz, 4 H), 4.16 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.72 (AA′m,

4 H), 3.58 (BB′m, 4 H), 3.39 (s, 6 H), 0.29 (s, 18 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.1, 133.2, 130.6, 128.1, 125.9,

115.3, 114.6, 103.9, 101.6, 95.2, 86.8, 71.9, 70.8, 69.6, 67.5, 59.1, 0.06.

842, 830, 811, 680, 648, 604, 538, 509 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.50 (d, J = 8.8 Hz, 2 H), 7.44 (d, J = 8.8

Hz, 2 H), 7.40 (ABq, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 6.88 (d, J = 8.8 Hz, 2

H), 4.17 (AA′m, 4 H), 3.88 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.59 (BB′m, 4

H), 3.40 (s, 6 H), 1.15 (m, 21 H).

MS (EI, 70 eV): m/z (%) = 706 ([M⁺], 100), 603 (10), 59 (15).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₄₂H₅₀O₆Si₂: 706.3146; found:

706.3160.

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.3, 159.1, 133.20,

133.14, 131.2, 130.3, 129.0, 127.9, 127.0, 125.7, 115.1, 114.9, 114.7,

114.5, 103.5, 101.3, 95.6, 95.5, 87.2, 86.7, 71.9 (2 C), 70.7 (2 C), 69.59,

69.57, 67.4 (2 C), 59.0 (2 C), 18.7, 11.3.

MS (EI, 70 eV): m/z (%) = 774 ([M⁺], 60), 772 ([M⁺], 60), 262 (100), 183

(46), 59 (50).

UV/VIS (MeCN): _max(log ) = 263 (sh, 4.56), 273 (4.62), 287 (4.66),

348 (4.70), 361 nm (sh, 4.66).

The second fraction revealed 11e as colorless needles; yield: 710 mg

(21%); mp 66–67 °C (MeOH).

IR (KBr): 3073, 2929, 2874, 2825, 2217, 1603, 1522, 1509, 1457, 1380,

1354, 1289, 1251, 1166, 1145, 1125, 1111, 1060, 1030, 974, 955, 923,

UV/VIS (MeCN): _max(log ) = 252 (4.53), 277 (4.54), 343 (4.68), 359

nm (sh, 4.61).

845, 761, 671, 619, 536 cm^–1

.

A last fraction contained recovered 7e; yield: 2.02 g (60%).

¹H NMR (400 MHz, CDCl₃):  = 7.50 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8

Hz, 2 H), 7.39 (br s, 2 H), 6.91 (AA′m, 2 H), 6.89 (BB′m, 2 H), 4.17

(AA′m, 4 H), 3.87 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.58 (BB′m, 4 H), 3.40

(br s, 6 H), 0.30 (s, 9 H).

4-(2-Bromo-3,6-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-

yl}phenyl)-2-methylbut-3-yn-2-ol (15d)

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.23, 159.18, 133.2 (2

C), 131.5, 129.2, 128.4, 127.7, 127.0, 125.6, 115.0, 114.8, 114.64,

114.59, 104.3, 101.8, 95.8, 95.6, 87.1, 86.7, 71.8 (2 C), 70.7 (2 C), 69.6

(2 C), 67.4 (2 C), 59.0 (2 C), –0.17.

2-Methylbut-3-yn-2-ol (750 L, 650 mg, 7.70 mmol) was reacted

with 7d (1.73 g, 3.00 mmol), following the experimental procedure

for the preparation of 7d. Column chromatography (silica gel, Et₂O)

separated first starting material 7d; yield: 674 mg (39%); followed by

15d as a yellow oil; yield: 633 mg (36%).

MS (EI, 70 eV): m/z (%) = 690 ([M⁺], 50), 688 ([M⁺], 50), 587 (20), 585

(20), 103 (30), 59 (100).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₃₇H₄₁⁸¹BrO₆Si: 690.1850; found:

690.1855.

IR (film): 3427, 2977, 2924, 2869, 2228, 1579, 1485, 1456, 1372,

1349, 1291, 1268, 1243, 1154, 1105, 1029, 963, 917, 840, 789, 748,

708, 666 cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.30 (ABq, 2 H), 4.48 (br s, 4 H), 3.81

(AA′m, 4 H), 3.72 (BB′m, 4 H), 3.67 (AA′m, 4 H), 3.60 (BB′m, 4 H), 3.531

(q, J = 7.0 Hz, 2 H), 3.524 (q, J = 7.0 Hz, 2 H), 1.64 (s, 6 H), 1.208 (t,

J = 7.0 Hz, 3 H), 1.202 (t, J = 7.0 Hz, 3 H).

¹³C NMR (125 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 131.6 (CH), 129.7 (CH),

128.1 (C_quat), 128.0 (C_quat), 126.3 (C_quat), 125.2 (C_quat), 103.5 (C_quat), 91.5

(C_quat), 91.3 (C_quat), 84.4 (C_quat), 84.2 (C_quat), 79.4 (C_quat), 70.5 (CH₂, 2 C),

70.2 (CH₂, 2 C), 69.57 (CH₂), 69.49 (CH₂), 69.12 (CH₂), 69.04 (CH₂), 66.4

(CH₂, 2 C), 65.1 (C_quat), 58.99 (CH₂), 58.85 (CH₂), 31.1 (CH₃), 14.97

(CH₃), 14.94 (CH₃).

UV/VIS (MeCN): _max(log ) = 251 (4.58), 275 (4.60), 343 (4.75), 353

nm (sh, 4.73).

The third fraction led to recovered starting material 7e; yield: 2.46 g

(73%).

3-Bromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)-2-[(triisopropylsilyl)ethynyl]benzene (13e)

(Triisopropylsilyl)acetylene (1.23 mL, 1.00 g, 5.48 mmol) was reacted

with 7e (3.36 g, 5.00 mmol) following the experimental procedure for

the preparation of 7d. Column chromatography (silica gel, EtOAc) led

first to 1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2,3-

bis[(triisopropylsilyl)ethynyl]benzene (14e) as light yellow needles;

yield: 48 mg (1%); mp 65–66 °C (EtOH).

MS (EI, 70 eV): m/z (%) = 580 ([M⁺], 0.2), 578 ([M⁺], 0.2), 562 (30), 560

(30), 489 (10), 487 (10), 428 (20), 426 (20), 189 (44), 117 (70), 73

(100), 59 (60).

UV/VIS (MeCN): _max(log ) = 248 (4.61), 255 (4.69), 277 (4.34),

284 (4.37), 294 nm (4.49).

IR (KBr): 2942, 2889, 2865, 2214, 2134, 1604, 1510, 1457, 1392, 1353,

1286, 1248, 1200, 1169, 1142, 1127, 1110, 1061, 999, 951, 936, 923,

Eluting the column with EtOAc gave 4,4′-(3,6-bis{3-[2-(2-ethoxye-

thoxy)ethoxy]prop-1-yn-1-yl}-1,2-phenylene)bis(2-methylbut-3-yn-

2-ol) (16d) as a yellow oil; yield: 160 mg (9%).

883, 836, 754, 679, 612, 592, 541 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.43 (d, J = 8.8 Hz, 4 H), 7.40 (s, 2 H),

6.87 (d, J = 8.8 Hz, 4 H), 4.17 (AA′m, 4 H), 3.88 (BB′m, 4 H), 3.73 (AA′m,

4 H), 3.59 (BB′m, 4 H), 3.40 (s, 6 H), 1.10 (m, 42 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.0, 133.1, 131.5, 127.6, 127.0,

115.4, 114.4, 103.3, 100.3, 94.8, 86.9, 71.9, 70.7, 69.6, 67.4, 59.0, 18.7,

11.4.

IR (film): 3416, 2978, 2930, 2868, 2227, 1461, 1407, 1350, 1294,

1252, 1224, 1170, 1104, 1036, 963, 919, 841, 769, 741, 673 cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.27 (s, 2 H), 4.47 (s, 4 H), 3.81 (AA′m,

4 H), 3.72 (BB′m, 4 H), 3.66 (AA′m, 4 H), 3.60 (BB′m, 4 H), 3.52 (q,

J = 7.0 Hz, 4 H), 2.51 (v br s, 2 H), 1.63 (s, 12 H), 1.20 (t, J = 7.0 Hz, 6 H).

I

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

¹³C NMR (125 MHz, CDCl₃):  = 130.4 (CH), 128.1 (C_quat), 124.9 (C_quat),

102.8 (C_quat), 90.6 (C_quat), 84.4 (C_quat), 79.1 (C_quat), 70.6 (CH₂), 70.3

(CH₂), 69.6 (CH₂), 69.1 (CH₂), 66.5 (CH₂), 65.3 (C_quat), 59.1 (CH₂), 31.3

(CH₃), 15.0 (CH₃).

MS (EI, 70 eV): m/z (%) = 564 ([M⁺– H₂O], 40), 491 (10), 297 (22), 283

(18), 281 (17), 269 (18), 253 (28), 239 (48), 226 (34), 215 (24), 213

(18), 202 (18), 189 (14), 117 (40), 103 (10), 73 (70), 59 (100).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.34, 159.31, 133.15,

133.04, 132.9, 131.7, 131.6, 129.7, 125.5, 114.67 (2 C), 114.65 (2 C),

108.7, 95.7, 95.1, 91.8, 88.1, 71.8 (2 C), 70.7 (2 C), 69.5 (2 C), 67.4 (2 C),

59.0 (2 C).

MS (EI, 70 eV): m/z (%) = 720 ([M⁺], 80), 718 ([M⁺], 80), 640 (5), 594

(20), 592 (20), 128 (10), 103 (20), 59 (100).

UV/VIS (MeCN): _max(log ) = 253 (sh, 4.58), 256 (sh, 4.63), 263 (4.79),

UV/VIS (MeCN): _max(log ) = 222 (4.63), 241 (4.60), 346 (4.86), 363

277 (4.47), 285 (4.27), 296 nm (4.45).

nm (sh, 4.80).

2-Bromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-

iodobenzene (17d)

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-2-iodo-3-

[(trimethylsilyl)ethynyl]benzene (18d)

To 7d (1.44 g, 2.50 mmol) in anhyd Et₂O (100 mL) was added 1.6 M

BuLi in hexane (1.9 mL, 3.0 mmol) at –110 °C. After stirring for 1 h, I₂

(950 mg, 3.74 mmol) in anhyd Et₂O (50 mL) was dripped in via cannu-

la. The mixture was stirred for an additional 30 min at –110 °C and

then allowed to warm to r.t. The resulting solution was washed first

with sat. aq Na₂S₂O₃, then H₂O, and dried (MgSO₄). The volatiles were

removed in vacuo and the residue subjected to column chromatogra-

phy (silica gel, Et₂O) to render 17d as a light yellow oil; yield: 1.00 g

(64%).

To 11d (1.48 g, 2.50 mmol) in anhyd THF (100 mL) at –110 °C was

added 1.6 M BuLi in hexane (1.9 mL, 3.0 mmol). After stirring for 1 h,

I₂(950 mg, 3.74 mmol) in anhyd THF (50 mL) was added dropwise via

cannula. The mixture was stirred for an additional 30 min at –110 °C

and then allowed to warm to r.t. The resulting solution was washed

first with sat. aq Na₂S₂O₃, then H₂O, and dried (MgSO₄). The volatiles

were removed in vacuo and the residue subjected to column chroma-

tography (silica gel, Et₂O) to give 18d as a light yellow oil; yield: 760

mg (47%).

IR (film): 2973, 2868, 2218, 1573, 1485, 1442, 1375, 1347, 1288,

IR (film): 2972, 2868, 2156, 1572, 1519, 1485, 1447, 1349, 1289,

1263, 1246, 1104, 1031, 967, 947, 840, 801, 723, 658 cm^–1

.

1250, 1116, 1033, 971, 945, 882, 845, 761, 701, 681, 661, 623 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.36 (d, J = 8.0 Hz, 1 H), 7.28 (d, J = 8.0

Hz, 1 H), 4.49 (s, 2 H), 4.48 (s, 2 H), 3.84–3.77 (m, 4 H), 3.75–3.69 (m,

4 H), 3.69–3.63 (m, 4 H), 3.63–3.57 (m, 4 H), 3.52 (q, J = 7.0 Hz, 4 H),

1.20 (t, J = 7.0 Hz, 6 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 133.2, 132.2, 131.6,

130.4, 125.3, 108.6, 91.6, 91.1, 88.8, 85.4, 70.6 (2 C), 70.3 (2 C), 69.7 (2

C), 69.3, 69.2, 66.5 (2 C), 58.9 (2 C), 15.1 (2 C).

MS (EI, 70 eV): m/z (%) = 624 ([M⁺], 5), 622 ([M⁺], 5), 551 (5), 549 (5),

490 (20), 488 (20), 117 (60), 73 (100), 59 (35).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₂₄H₃₂⁷⁹BrIO₆: 622.0444; found:

622.0440.

¹H NMR (400 MHz, CDCl₃):  = 7.33 (d, J = 8.0 Hz, 1 H), 7.24 (d, J = 8.0

Hz, 1 H), 4.48 (s, 2 H), 4.47 (s, 2 H), 3.83 (m, 2 H), 3.77 (m, 2 H), 3.74–

3.68 (m, 4 H), 3.68–3.63 (m, 4 H), 3.62–3.57 (m, 4 H), 3.518 (q, J = 7.0

Hz, 2 H), 3.513 (q, J = 7.0 Hz, 2 H), 1.199 (t, J = 7.0 Hz, 3 H), 1.194 (t,

J = 7.0 Hz, 3 H), 0.27 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 132.7, 131.18, 131.14,

130.2, 125.6, 107.4, 105.3, 103.8, 91.3, 90.8, 88.3, 84.4, 70.65 (2 C),

70.63, 70.4, 69.74, 69.73, 69.29, 69.15, 66.6 (2 C), 59.01, 58.98, 15.11,

15.09, –0.30.

MS (EI, 70 eV): m/z (%) = 640 ([M⁺], 30), 567 (10), 523 (10), 506 (25),

389 (10), 375 (117 (40), 103 (10), 73 (100), 59 (30).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₂₉H₄₁IO₆Si: 640.1717; found:

640.1725.

UV/VIS (MeCN): _max(log ) = 224 (4.32), 237 (4.31), 272 (sh, 4.33),

278 (sh, 4.36), 281 (4.42), 292 nm (4.40).

UV/VIS (MeCN): _max(log ) = 243 (sh, 4.41), 256 (sh, 4.57), 262 (4.63),

279 (4.32), 287 (4.29), 298 nm (4.35).

2-Bromo-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)benzene (17e)

3-Iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-

2-[(trimethylsilyl)ethynyl]benzene (18e)

Dibromide 7e (1.68 g, 2.50 mmol) was subjected to the protocol for

the synthesis of 17d. Column chromatography (silica gel, EtOAc) be-

got 17e as colorless crystals; yield: 1.52 g (85%); mp 102–103 °C

(EtOH).

Compound 11e (1.73 g, 2.50 mmol) was reacted according to the pro-

cedure described for the synthesis of 18d from 11d. Column chroma-

tography (silica gel, EtOAc) furnished 18e as colorless needles; yield:

1.48 g (80%); mp 74–76 °C (MeOH).

IR (KBr): 3068, 2986, 2875, 2823, 2221, 1602, 1570, 1516, 1491, 1471,

1457, 1450, 1382, 1364, 1353, 1342, 1331, 1303, 1280, 1250, 1196,

1166, 1145, 1123, 1101, 1061, 1028, 1006, 955, 936, 924, 903, 887,

IR (KBr): 2927, 2873, 2823, 2214, 2155, 1602, 1568, 1522, 1507, 1467,

1456, 1414, 1370, 1353, 1302, 1287, 1250, 1201, 1165, 1144, 1125,

1110, 1059, 1029, 968, 954, 936, 923, 843, 812, 761, 703, 671, 646,

855, 842, 827, 812, 787, 706, 644, 626, 536 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.51 (d, J = 8.8 Hz, 2 H), 7.48 (d, J = 8.8

Hz, 2 H), 7.45 (d, J = 8.0 Hz, 1 H), 7.37 (d, J = 8.0 Hz, 1 H), 6.91 (d,

J = 8.8 Hz, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.16 (m, 4 H), 3.87 (m, 4 H),

3.72 (m, 4 H), 3.58 (m, 4 H), 3.39 (s, 6 H).

¹H NMR (400 MHz, C₆D₆):  = 7.53 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8

Hz, 2 H), 7.09 (d, J = 8.0 Hz, 1 H), 7.02 (d, J = 8.0 Hz, 1 H), 6.72 (d,

J = 8.8 Hz, 2 H), 6.68 (d, J = 8.8 Hz, 2 H), 3.68 (m, 4 H), 3.51 (m, 4 H),

3.45 (m, 4 H), 3.33 (m, 4 H), 3.12 (s, 6 H).

618, 536 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.52 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8

Hz, 2 H), 7.41 (d, J = 8.0 Hz, 1 H), 7.34 (d, J = 8.0 Hz, 1 H), 6.91 (d,

J = 8.8 Hz, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.17 (m, 4 H), 3.88 (m, 4 H),

3.73 (m, 4 H), 3.58 (m, 4 H), 3.40 (s, 6 H), 0.31 (s, 9 H).

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.26, 159.19, 133.15,

133.05, 132.3, 130.59, 130.54, 130.4, 125.9, 115.1, 114.9, 114.69,

114.62, 107.5, 105.8, 103.4, 95.7, 94.7, 91.2, 87.0, 71.9 (2 C), 70.7 (2 C),

69.6 (2 C), 67.4 (2 C), 59.0 (2 C), –0.21.

J

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

MS (EI, 70 eV): m/z (%) = 736 ([M⁺], 90), 610 (100), 633 (5), 103 (10),

2-Ethynyl-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)benzene (20e) from 18e

59 (60⁺).

Compound 18e (1.47 g, 2.00 mmol) was converted according to the

procedure described for the synthesis of 20d from 18d. Column chro-

matography (silica gel, EtOAc) presented 20e as light yellow needles;

yield: 1.27 g (96%); mp 88–90 °C (EtOH).

UV/VIS (MeCN): _max(log ) = 236 (sh, 4.38), 258 (4.49), 273 (sh, 4.47),

345 (4.74), 361 nm (sh, 4.69).

3-Iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-

2-[(triisopropylsilyl)ethynyl]benzene (19e)

IR (KBr): 3246, 2940, 2927, 2878, 2828, 2809, 2216, 1602, 1569, 1519,

1508, 1490, 1471, 1456, 1356, 1333, 1303, 1287, 1249, 1195, 1168,

1139, 1121, 1098, 1062, 1030, 951, 937, 923, 852, 840, 827, 811, 792,

Bromoarene 13e (1.945 g, 2.50 mmol) was transformed following the

procedure described for the synthesis of 18d from 11d. Column chro-

matography (silica gel, EtOAc) produced 19e as light yellow needles;

yield: 1.595 g (78%); mp 103–104 °C (EtOH).

650, 614, 544, 534 cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.51 (d, J = 8.8 Hz, 2 H), 7.46 (d, J = 8.8

Hz, 2 H), 7.43 (d, J = 8.0 Hz, 1 H), 7.37 (d, J = 8.0 Hz, 1 H), 6.89 (ABq, 4

H), 4.15 (m, 4 H), 3.86 (m, 4 H), 3.71 (m, 4 H), 3.72 (s, 1 H), 3.60 (m, 4

H), 3.38 (s, 6 H).

¹³C NMR (125 MHz, CDCl₃):  = 159.34, 159.31, 133.26, 133.1, 132.3,

131.0, 130.70, 130.5, 126.6, 114.94, 114.85, 114.73, 114.69, 107.2,

95.9, 95.0, 91.1, 86.8, 85.2, 84.7, 71.9 (2 C), 70.7 (2 C), 69.6 (2 C), 67.5

(2 C), 59.0 (2 C).

IR (KBr): 2941, 2925, 2885, 2864, 2217, 2146, 1602, 1567, 1519, 1509,

1453, 1358, 1308, 1286, 1246, 1202, 1168, 1138, 1111, 1060, 1018,

996, 966, 950, 921, 883, 842, 831, 810, 770, 680, 647, 604, 537, 508

cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.52 (d, J = 8.8 Hz, 2 H), 7.44 (d, J = 8.0

Hz, 1 H), 7.43 (d, J = 8.8 Hz, 2 H), 7.34 (d, J = 8.0 Hz, 1 H), 6.91 (d,

J = 8.8 Hz, 2 H), 6.88 (d, J = 8.8 Hz, 2 H), 4.17 (m, 4 H), 3.87 (m, 4 H),

3.73 (m, 4 H), 3.59 (m, 4 H), 3.40 (s, 6 H), 1.15 (m, 21 H).

MS (EI, 70 eV): m/z (%) = 664 ([M⁺], 75), 561 (3), 538 (9), 514 (6), 254

¹³C NMR (100 MHz, CDCl₃, number of accidentally isochronous peaks

based on relative peak heights or widths):  = 159.2, 159.1, 133.2,

133.0, 132.2, 131.3, 131.0, 130.3, 126.1, 115.1, 115.0, 114.7, 114.4,

107.9, 107.1, 100.4, 95.3, 94.7, 91.2, 86.9, 71.9 (2 C), 70.7 (2 C), 69.58,

69.55, 67.4 (2 C), 59.0 (2 C), 18.7, 11.3.

(10), 155 (20), 142 (70), 127 (50), 103 (10), 59 (100).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₃₄H₃₃IO₆: 664.1322; found:

664.1332.

UV/VIS (MeCN): _max(log ) = 257 (4.63), 344 (4.77), 354 (sh, 4.75),

362 nm (sh, 4.74).

MS (EI, 70 eV): m/z (%) = 820 ([M⁺], 100), 694 (40), 103 (5), 59 (30).

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₄₃H₅₃IO₆Si: 820.2656; found:

820.2671.

2-Ethynyl-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)benzene (20e) from 19e

Compound 19e (1.64 g, 2.00 mmol) in THF (75 mL) was subjected to 1

M TBAF in THF (2.20 mL, 2.20 mmol) at r.t. The solution, which turned

yellow immediately, was stirred for 30 min (TLC monitoring), then di-

luted with CH₂Cl₂(200 mL), washed with H₂O (3 × 100 mL), and dried

(MgSO₄). After removal of the volatiles under reduced pressure, col-

umn chromatography (silica gel, EtOAc) afforded 20e; yield: 1.29 g

(97%).

UV/VIS (MeCN): _max(log ) = 258 (4.63), 280 (4.61), 344 (4.76), 360

nm (sh, 4.68).

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-ethynyl-

2-iodobenzene (20d)

To 18d (1.28 g, 2.00 mmol) in MeOH (100 mL) was added sat. aq

K₂CO₃(1 mL, 8 mmol) at r.t. The resulting cloudy solution was stirred

at r.t. until clear (30 min), diluted with CH₂Cl₂(200 mL), washed with

H₂O (3 × 100 mL), dried (MgSO₄), and the volatiles were removed un-

der reduced pressure. Column chromatography (silica gel, Et₂O) re-

sulted in 20d as a heat- and light-sensitive, light yellow oil; yield:

1.12 g (99%).

1,4,7,10,13,16-Hexakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-

ynyl}tribenzo[a,e,i]cyclododeca-5,11,17-triyne (2d)

To CuCl (99 mg, 1.00 mmol) in aq NH₃(60 mL) was added dropwise

20d (568 mg, 1.00 mmol) in EtOH (60 mL). After stirring for 1 h at r.t.,

the resulting yellowish orange precipitate was collected by filtration,

washed with H₂O, and dried under high vacuum overnight. The cu-

prate was dissolved in pyridine (75 mL) and the solution heated to re-

flux over a period of 6 h. After cooling to r.t., the volatiles were re-

moved under reduced pressure, and the resulting dark brown residue

was subjected to column chromatography (silica gel, Et₂O/THF 2:1) to

supply 2d as a yellow oil; yield: 104 mg (24%).

IR (film): 3235, 2973, 2868, 2104, 1573, 1519, 1485, 1448, 1349,

1287, 1266, 1247, 1115, 1033, 971, 946, 839, 763, 748, 693, 670, 623

cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.29 (d, J = 8.1 Hz, 1 H), 7.23 (d, J = 8.1

Hz, 1 H), 4.42 (s, 2 H), 4.41 (s, 2 H), 3.75 (m, 4 H), 3.69 (s, 1 H), 3.65 (m,

4 H), 3.60 (m, 4 H), 3.53 (m, 4 H), 3.45 (q, J = 7.0 Hz, 4 H), 1.139 (t,

J = 7.0 Hz, 3 H), 1.135 (t, J = 7.0 Hz, 3 H).

¹³C NMR (125 MHz, CDCl₃):  = 131.7, 131.4, 131.0, 130.2, 126.1,

106.9, 91.5, 90.9, 88.1, 85.7, 84.12, 84.08, 70.49, 70.48, 70.24, 70.20,

69.60, 69.59, 69.2, 68.9, 66.41, 66.40, 58.84, 58.82, 14.98, 14.96.

MS (EI, 70 eV): m/z (%) = 568 ([M⁺], 2), 495 (1), 434 (3), 377 (1), 277

(100), 262 (10), 209 (7), 201 (15), 199 (15), 183 (16), 149 (16), 117

(17), 103 (10), 73 (55), 59 (50).

IR (film): 2971, 2917, 2868, 2223, 1467, 1375, 1348, 1287, 1247,

1104, 1032, 946, 840, 767, 734, 688, 633 cm^–1

.

¹H NMR (300 MHz, CDCl₃):  = 7.27 (s, 6 H, CH), 4.45 (s, 12 H), 3.74

(AA′m, 12 H), 3.65 (BB′m, 12 H), 3.61 (AA′m, 12 H), 3.55 (BB′m, 12 H),

3.49 (q, J = 7.0 Hz, 12 H), 1.18 (t, J = 7.0 Hz, 18 H).

¹³C NMR (100 MHz, CDCl₃):  = 132.5, 128.9, 125.6, 95.8, 91.8, 84.1,

70.5, 70.2, 69.6, 69.1, 66.5, 59.1, 15.0.

HRMS (EI, 70 eV): m/z [M⁺] calcd for C₂₆H₃₃IO₆: 568.1322; found:

568.1332.

MS (FAB, 70 eV): m/z (%) = 1321.6 ([MH⁺]).

UV/VIS (MeCN): _max(log ) = 200 (4.55), 232 (sh, 4.41), 247 (4.60),

273 (4.70), 297 (4.68), 311 (4.64), 319 (4.59), 334 (4.81), 400 nm

(2.96).

UV/VIS (MeCN): _max(log ) = 254 (4.50), 277 (4.30), 283 (4.31), 294

nm (4.43).

K

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

1,4,7,10,13,16-Hexakis({4-[2-(2-methoxyethoxy)ethoxy]phe-

2,3-Diethynyl-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phe-

nyl}ethynyl)tribenzo[a,e,i]cyclododeca-5,11,17-triyne (2e)

nyl}ethynyl)benzene (21e)

The recipe for the preparation of 2d from 20d was followed, except

the solvent for 20e (664 mg, 1.00 mmol) was EtOH/DMSO (1:2, 60

mL). Column chromatography (silica gel, EtOAc/acetone 4:1) seques-

tered 2e as yellow crystals; yield: 122 mg (23%); mp 118–119 °C

(EtOAc/hexane).

From 12e: Compound 12e (1.41 g, 2.00 mmol) was subjected to the

reaction conditions used for the synthesis of 21d from 12d. Column

chromatography (silica gel, EtOAc) gave 21e as heat- and light-sensi-

tive, light brown needles; yield: 1.04 g (92%); mp >50 °C dec (EtOH).

From 14e: Compound 14e (1.75 g, 2.00 mmol) in THF (75 mL) was ex-

posed to 1 M TBAF in THF (2.2 mL, 2.2 mmol) at r.t. The solution

turned yellow immediately and was stirred for 30 min. It was then di-

luted with CH₂Cl₂(200 mL), washed with H₂O (3 × 100 mL), dried

(MgSO₄), and the volatiles removed under reduced pressure. Work up

of the residue as described above supplied 21e; yield: 1.11 g (99%).

IR (KBr): 3069, 3042, 2923, 2876, 2823, 2198, 1604, 1567, 1511, 1462,

1417, 1356, 1288, 1250, 1199, 1169, 1139, 1127, 1109, 1059, 1028,

923, 830, 764, 627, 608, 535 cm^–1

.

¹H NMR (500 MHz, CDCl₃):  = 7.39 (s, 6 H), 7.16 (d, J = 8.8 Hz, 12 H),

6.60 (d, J = 8.8 Hz, 12 H), 4.08 (AA′m, 12 H), 3.84 (BB′m, 12 H), 3.72

(AA′m, 12 H), 3.58 (BB′m, 12 H), 3.40 (s, 18 H).

¹³C NMR (125 MHz, CDCl₃):  = 158.6, 133.5, 131.8, 128.6, 126.1,

115.3, 113.9, 96.5, 96.5, 86.9, 71.9, 70.8, 69.7, 67.4, 59.1.

MS (FAB, 70 eV): m/z (%) = 1609.6 ([MH⁺]).

HRMS (FAB): m/z [M⁺] calcd for C₁₀₂H₉₆O₁₈: 1608.6597; found:

IR (KBr): 3261, 3073, 2927, 2882, 2829, 2208, 2109, 1602, 1512, 1467,

1450, 1356, 1290, 1252, 1203, 1174, 1163, 1138, 1110, 1057, 982,

949, 939, 923, 845, 828, 809, 769, 714, 664, 615, 533 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.48 (d, J = 8.8 Hz, 4 H), 7.44 (s, 2 H),

6.90 (d, J = 8.8 Hz, 4 H), 4.16 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.72 (AA′m,

4 H), 3.64 (s, 2 H), 3.58 (BB′m, 4 H), 3.39 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.3, 133.3, 131.1, 127.4, 126.4,

115.0, 114.7, 95.7, 86.5, 85.4, 80.5, 71.9, 70.8, 69.6, 67.5, 59.0.

1608.6542.

UV/VIS (MeCN): _max(log ) = 235 (sh, 4.51), 256 (4.80), 303 (sh, 4.75),

350 (5.20), 378 (sh, 4.99), 439 nm (3.69).

MS (FAB, 70 eV): m/z (%) = 562 ([M⁺]).

Fluorescence (MeCN, _exc= 350 nm): _em= 499 nm.

UV/VIS (MeCN): _max(log ) = 255 (4.52), 266 (sh, 4.46), 346 (4.67),

362 nm (sh, 4.62).

High Yield Preparation of 12d,e and 14e from 7d,e

(Trimethylsilyl)acetylene (1.14 mL, 786 mg, 8 mmol) or (triisopropyl-

silyl)acetylene (1.80 mL, 1.46 g, 8 mmol) in a Fisher–Porter bottle was

injected in one portion into a mixture of the respective alkynylated

1,4,9,12-Tetrakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-

yl}dibenzo[a,g]cyclododeca-5,7,13,15-tetrayne (4a) and

1,4,9,12,17,20-Hexakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-

1-yl}tribenzo[a,g,m]cyclooctadeca-5,7,13,15,21,23-hexayne (22d)

2,3-dibromobenzenes

7d,e

(2 mmol),

Cl₂Pd(PPh₃)₂

(70 mg,

0.10 mmol), and CuI (19 mg, 0.10 mmol) in Et₃N (100 mL) at r.t. The

vessel was sealed and the mixture stirred at 100 °C for 6 h. During this

time the solution rapidly turned bright yellow, then yellow brown,

and finally dark brown with the formation of a precipitate. After cool-

ing to r.t., an additional portion of the silylalkyne (4 mmol) was add-

ed, the mixture stirred again at 100 °C for 6 h, allowed to cool to r.t.,

and filtered. The solvent was evaporated and the resulting residue pu-

rified by column chromatography (silica gel, Et₂O) to present, respec-

tively, 12d as a yellow oil; yield: 1.00 g (82%); 12e as a yellow oil;

yield: 1.10 g (78%); and 14e as yellow crystals; yield: 1.00 g (57%).

Through a solution of 21d (933 mg, 2.00 mmol) and CuCl (238 mg,

2.40 mmol) in chlorobenzene (125 mL) was passed a continuous

stream of dry O₂for 15 min to ensure saturation. TMEDA (10 mL) was

then added dropwise under vigorous stirring at r.t. The mixture im-

mediately turned yellow, then green, and finally cloudy dark green

with the formation of a precipitate upon completion of the addition.

After stirring for an additional 1 h under O₂, the reaction was

quenched with 1 M aq HCl (100 mL), CH₂Cl₂(100 mL) added, the mix-

ture shaken, the organic layer collected, and the aqueous layer further

extracted with CH₂Cl₂(5 × 100 mL). The combined organic phases

were washed with sat. aq NaHCO₃and then H₂O. The volatiles were

removed under reduced pressure and the resulting solid yellow

brown residue was subjected to column chromatography (silica gel,

Et₂O/THF 5:1), leading to a first fraction containing air-sensitive 4a

forming golden plates; yield: 360 mg (39%); mp 104–105 °C dec

(CH₂Cl₂/hexane).

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-2,3-di-

ethynylbenzene (21d)

To 12d (1.22 g, 2.00 mmol) in MeOH (100 mL) was added sat. aq

K₂CO₃(1 mL, 8 mmol) at r.t. The resulting cloudy solution was stirred

until clear (30 min), diluted with CH₂Cl₂(200 mL), washed with H₂O

(3 × 100 mL), dried (MgSO₄), and the volatiles were removed under

reduced pressure. Column chromatography (silica gel, Et₂O) resulted

in 21d as a heat- and light-sensitive, light yellow oil, stored at 0 °C;

yield: 910 mg (98%).

IR (KBr): 2973, 2911, 2869, 2222, 2121, 1480, 1456, 1443, 1375, 1346,

1289, 1261, 1245, 1118, 1099, 1088, 1029, 951, 852, 835, 664, 626

cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.06 (s, 4 H), 4.42 (s, 8 H), 3.73 (AA′m,

8 H), 3.69 (BB′m, 8 H), 3.65 (AA′m, 8 H), 3.60 (BB′m, 8 H), 3.52 (q,

J = 7.0 Hz, 8 H), 1.20 (t, J = 7.0 Hz, 12 H).

¹³C NMR (100 MHz, CDCl₃):  = 133.3, 132.3, 122.8, 91.9, 91.6, 87.3,

83.2, 70.6, 70.3, 69.7, 69.2, 66.5, 58.9, 15.1.

MS (FAB, 70 eV): m/z (%) = 929.5 ([MH⁺]).

HRMS (FAB, 70 eV): m/z [MH⁺] calcd for C₅₆H₆₅O₁₂: 929.4476; found:

IR (film): 3280, 3236, 2974, 2868, 2227, 2105, 1573, 1485, 1461,

1394, 1376, 1349, 1282, 1246, 1101, 1033, 946, 839, 642 cm^–1

.

¹H NMR (300 MHz, CDCl₃):  = 7.34 (s, 2 H), 4.47 (s, 4 H), 3.81 (AA′m,

4 H), 3.70 (BB′′m, 4 H), 3.65 (AA′m, 4 H), 3.61 (s, 2 H), 3.58 (BB′m, 4 H),

3.51 (q, J = 7.0 Hz, 4 H), 1.19 (t, J = 7.0 Hz, 6 H).

¹³C NMR (100 MHz, CDCl₃):  = 131.3, 127.6, 125.8, 91.3, 85.9, 83.9,

79.8, 70.5, 70.2, 69.6, 68.9, 66.4, 58.8, 15.0.

929.4480.

MS (FAB, 70 eV): m/z (%) = 467 ([MH⁺]).

UV/VIS (MeCN): _max(log ) = 212 (4.68), 245 (sh, 4.70), 250 (4.77),

275 (sh, 4.64), 280 (sh, 4.70), 286 (4.81), 295 (sh, 4.63), 302 (sh, 4.51),

317 (4.77), 324 (4.57), 327 (sh, 4.54), 339 (5.06), 420 nm (3.94).

UV/VIS (MeCN): _max(log ) = 247 (sh, 4.53), 253 (4.61), 257 (4.64),

277 (4.30), 283 (4.34), 294 nm (4.50).

L

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

Fluorescence (MeCN, _exc= 340 nm): _em= 501, 539, 548 nm.

¹³C NMR (125 MHz, CD₂Cl₂):  = 159.4, 159.2, 158.8, 151.9, 149.8,

147.1, 134.7, 134.2, 133.9, 132.5, 130.7, 130.6, 129.2, 128.9, 126.6,

125.9, 118.4 (2 C), 116.7, 116.0, 115.7, 114.6, 114.5, 114.4, 97.4, 95.5,

94.9, 94.1, 88.2, 87.4, 72.5 (3 C), 71.24 (2 C), 71.20, 70.20, 70.12, 70.11,

68.10, 68.08, 68.04, 59.3 (3 C).

MS (FAB, 70 eV): m/z (%) = 1609.9 ([MH⁺]).

HRMS (FAB, 70 eV): m/z [M⁺] calcd for C₁₀₂H₉₆O₁₈: 1608.6597; found:

On switching the chromatography solvent to Et₂O/THF (2:1), a second

fraction emerged containing 22d as a yellow oil; yield: 36 mg (4%).

¹H NMR (500 MHz, CDCl₃):  = 7.46 (s, 6 H), 4.55 (s, 12 H), 3.85 (AA′m,

12 H), 3.73 (BB′m, 12 H), 3.64 (AA′m, 12 H), 3.58 (BB′m, 12 H), 3.49 (q,

J = 7.0 Hz, 12 H), 1.18 (t, J = 7.0 Hz, 18 H).

¹³C NMR (100 MHz, CDCl₃):  = 132.1, 127.5, 126.6, 92.6, 83.8, 82.0,

80.3, 70.6, 70.4, 69.8, 69.2, 66.6, 59.1, 15.1.

1608.6622.

UV/VIS (MeCN): _max(log ) = 261 (5.16), 309 (5.18), 344 (5.32), 422

(4.64), 441 (sh, 4.59), 465 (sh, 4.40), 538 nm (3.78).

1,4,9,12-Tetrakis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}-

ethynyl)dibenzo[a,g]cyclododeca-5,7,13,15-tetrayne (4b) and

1,4,9,12,17,20-Hexakis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}-

ethynyl)tribenzo[a,g,m]cyclooctadeca-5,7,13,15,21,23-hexayne

(22e)

Fluorescence (MeCN, _exc= 350 nm): _em= 568 nm.

Cobalt-Catalyzed Cycloisomerization of 23 to 24

Angular [3]phenylene derivative 23 (56 mg, 0.035 mmol) and

CpCo(CO)₂(33 L, 45 mg, 0.25 mmol) in tetraglyme (30 mL) were

added in one portion to boiling tetraglyme (120 mL). The mixture was

maintained at reflux for 25 min, while being irradiated with a 300 W

projector lamp at 60 V. During this time, the solution turned deep red

possessing an orange fluorescence. After removal of the solvent under

vacuum, the residue was subjected to column chromatography (silica

gel, EtOAc/acetone 3:1) to give 24 as a deep red solid; yield: 12 mg

(21%).

Following the procedure executed for the synthesis of 4a and 22d, ox-

idative coupling of 21e (1.12 g, 2.00 mmol), followed by column chro-

matography (silica gel, EtOAc/acetone 4:1), afforded first 4b as air-

sensitive yellow crystals; yield: 270 mg (24%); mp 30–40 °C dec (tolu-

ene).

IR (KBr): 3070, 3044, 2925, 2876, 2823, 2211, 1604, 1570, 1514, 1474,

1453, 1355, 1285, 1250, 1199, 1167, 1130, 1110, 1059, 923, 827, 649,

605, 535, 487 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.47 (d, J = 8.8 Hz, 8 H), 7.13 (s, 4 H),

6.89 (d, J = 8.8 Hz, 8 H), 4.17 (AA′m, 8 H), 3.88 (BB′m, 8 H), 3.73 (AA′m,

8 H), 3.58 (BB′m, 8 H), 3.39 (s, 12 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.4, 133.5, 132.9, 132.1, 123.3,

114.73, 114.67, 96.0, 92.1, 87.5, 85.9, 72.0, 70.8, 69.7, 67.5, 59.1.

MS (FAB, 70 eV): m/z (%) = 1120.6 ([M⁺]).

HRMS (FAB, 70 eV): m/z [M⁺] calcd for C₇₂H₆₄O₁₂: 1120.4398; found:

IR (KBr): 2924, 2855, 2203, 1606, 1511, 1455, 1384, 1355, 1286, 1250,

1199, 1178, 1109, 1063, 927, 825 cm^–1

.

¹H NMR (500 MHz, CD₂Cl₂):  = 7.12 (d, J = 8.8 Hz, 4 H), 6.94 (d, J = 8.8

Hz, 4 H), 6.93 (d, J = 8.8 Hz, 4 H), 6.90 (d, J = 7.3 Hz, 2 H), 6.73 (d,

J = 8.8 Hz, 4 H), 6.69 (d, J = 8.8 Hz, 4 H), 6.52 (d, J = 8.8 Hz, 4 H), 6.40

(d, J = 7.3 Hz, 2 H), 6.18 (s, 2 H), 4.08 (m, 8 H), 4.00 (m, 4 H), 3.80 (m,

12 H), 3.66 (m, 12 H), 3.54 (m, 12 H), 3.357 (s, 6 H), 3.354 (s, 6 H),

3.349 (s, 6 H).

MS (FAB, 70 eV): m/z (%) = 1609.8 ([MH⁺]).

HRMS (FAB, 70 eV): m/z [M⁺] calcd for C₁₀₂H₉₆O₁₈: 1608.6597; found:

1120.4408.

UV/VIS (MeCN): _max(log ) = 248 (sh, 4.77), 255 (4.84), 346 (5.05),

367 (5.02), 457 nm (3.94).

1608.6598.

Fluorescence (MeCN, _exc= 365 nm): _em= 502, 545, 555 nm.

UV/VIS (MeCN): _max(A) = 282 (0.44), 296 (sh, 0.40), 347 (0.31), 396

(sh, 0.15), 487 (0.02), 525 (sh, 0.01), 583 nm (0.01).

A second fraction contained waxy, impure 22e, characterized solely

by a ¹H NMR spectrum; (maximum) yield: 16 mg (1.4%).

Fluorescence (MeCN, _exc= 350 nm): _em= 594 nm.

¹H NMR (300 MHz, CDCl₃):  = 7.53 (s, 6 H), 7.35 (d, J = 8.8 Hz, 12 H),

6.56 (d, J = 8.8 Hz, 12 H), 3.98 (m, 12 H), 3.82 (m, 12 H), 3.72 (m, 12 H),

3.59 (m, 12 H), 3.41 (s, 18 H).

3,6,9,16,19,22-Hexaoxatetracosa-11,13-diyne (5a)

Through a solution of 6a (1.72 g, 10 mmol) and CuCl (119 mg,

1.20 mmol) in acetone (75 mL) was passed a continuous stream of dry

O₂for 15 min to ensure saturation. TMEDA (1 mL) was then added in

one portion under vigorous stirring at r.t. The mixture immediately

turned green and then dark green with the formation of a precipitate.

After stirring for an additional 4 h under O₂, the reaction was

quenched with 1 M aq HCl (75 mL), CH₂Cl₂(100 mL) added, the mix-

ture shaken, the organic layer collected, and the aqueous layer further

extracted with CH₂Cl₂(5 × 100 mL). The combined organic phases

were washed with sat. aq NaHCO₃, then H₂O, and finally dried

(MgSO₄). The volatiles were removed under reduced pressure, and the

resulting solid yellow brown residue was subjected to column chro-

matography (silica gel, Et₂O) to provide 5a as a light-sensitive, light

yellow oil; yield: 1.41 g (82%).

Cobalt-Catalyzed Cycloisomerization of 2e to 23

To boiling m-xylene (120 mL) was added 2e (120 mg, 0.075 mmol)

and CpCo(CO)₂(33 L, 45 mg, 0.25 mmol) in m-xylene (30 mL) in one

portion. The mixture was maintained at reflux for 25 min, while be-

ing irradiated with a 300 W slide projector lamp at 60 V. During this

time, the solution turned deep red exhibiting a yellow fluorescence.

After removal of the solvent under vacuum, the residue was subjected

to column chromatography (silica gel, EtOAc/acetone 3:1) to give 23

as a red solid; yield: 72 mg (60%).

IR (KBr): 2923, 2875, 2824, 2197, 1605, 1511, 1453, 1355, 1287, 1250,

1171, 1128, 1110, 1061, 934, 925, 830, 534 cm^–1

.

¹H NMR (500 MHz, CD₂Cl₂):  = 7.36 (s, 2 H), 7.20 (d, J = 8.6 Hz, 4 H),

7.15 (d, J = 8.6 Hz, 4 H), 7.10 (d, J = 7.4 Hz, 2 H), 7.06 (d, J = 8.6 Hz, 4

H), 6.80 (d, J = 8.6 Hz, 4 H), 6.62 (d, J = 7.4 Hz, 2 H), 6.60 (ABq, 8 H),

4.08 (m, 4 H), 4.04 (m, 8 H), 3.80 (m, 12 H), 3.66 (m, 12 H), 3.54 (m, 12

H), 3.36 (s, 12 H), 3.35 (s, 6 H).

IR (film): 2974, 2869, 2253, 2177, 2120, 1486, 1457, 1443, 1376,

1348, 1290, 1246, 1093, 1030, 999, 945, 921, 844 cm^–1

.

¹H NMR (300 MHz, CDCl₃):  = 4.27 (s, 4 H), 3.68 (m, 8 H), 3.65 (AA′m,

4 H), 3.60 (BB′m, 4 H), 3.52 (q, J = 7.0 Hz, 4 H), 1.21 (t, J = 7.0 Hz, 6 H).

¹³C NMR (100 MHz, C₆D₆):  = 76.8, 71.4, 71.2, 71.1, 70.7, 70.1, 67.0,

59.1, 15.8.

M

U. Dahlmann, K. P. C. Vollhardt

Paper

Synthesis

MS (FAB, 70 eV): m/z (%) = 343.2 ([MH⁺]).

HRMS (FAB, 70 eV): m/z [MH⁺] calcd for C₁₈H₃₁O₆: 343.2121; found:

(2) (a) Eickmeier, C.; Junga, H.; Matzger, A. J.; Scherhag, F.; Shim,

M.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1997, 36, 2103.

(b) For the X-ray structure of 2a, see: Matzger, A. J.; Shim, M.;

Vollhardt, K. P. C. Chem. Commun. 1999, 1871. (c) For calculated

structures of 2a and 22a, see: Juselius, J.; Sundholm, D. Phys.

Chem. Chem. Phys. 2001, 3, 2433. (d) For ¹H NMR evidence of 1a,

see: Fonari, A.; Röder, J. C.; Shen, H.; Timofeeva, T. V.; Vollhardt,

K. P. C. Synlett 2014, 25, 2429. (e) The name ‘antikekulene’ was

coined by us to highlight the juxtaposition of 2a to the all-

aromatic and -benzenoid hydrocarbon kekulene: Diercks, R.;

Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1986, 25, 266.

(3) For a related attempt to synthesize an isomer of the circular

[8]phenylene framework see: Miljanić, O. Š.; Holmes, D.;

Vollhardt, K. P. C. Org. Lett. 2005, 7, 4001.

(4) For a review, see: Miljanič, O. Š.; Vollhardt, K. P. C. In Carbon-

Rich Compounds: From Molecules to Materials; Haley, M. M.;

Tykwinski, R. R., Ed.; Wiley-VCH: Weinheim, 2006, 140.

(5) For selected illustrative computational assessments, see:

(a) Gribanova, T. N.; Minyaev, R. M.; Minkin, V. I. Russ. J. Org.

Chem. 2016, 52, 268. (b) Dickens, T. K.; Mallion, R. B. Chem. Phys.

Lett. 2011, 517, 98. (c) Aihara, J. J. Phys. Chem. A 2008, 112, 4382.

(d) Schulman, J. M.; Disch, R. L. J. Phys. Chem. A 2007, 111,

10010; and references cited therein. (e) Kataoka, M. J. Tohoku

Pharm. Univ. 2006, 53, 125.

343.2119.

1,4-Bis{4-[2-(2-methoxyethoxy)ethoxy]phenyl}buta-1,3-diyne

(5b)

In a replication of the manner in which 5a was assembled, 6b (2.20 g,

10 mmol) was subjected to oxidative coupling and purified by column

chromatography (silica gel, EtOAc) to create 5b as colorless crystals;

yield: 1.98 g (90%); mp 84–85 °C (EtOH).

IR (KBr): 3074, 3045, 2971, 2943, 2913, 2878, 2140, 1639, 1599, 1504,

1466, 1451, 1399, 1380, 1357, 1307, 1285, 1248, 1201, 1171, 1141,

1120, 1079, 1058, 1032, 960, 953, 942, 923, 851, 829, 721, 640, 574,

537, 456 cm^–1

.

¹H NMR (400 MHz, CDCl₃):  = 7.44 (d, J = 6.0 Hz, 4 H), 6.86 (d, J = 6.0

Hz, 4 H), 4.15 (AA′m, 4 H), 3.86 (BB′m, 4 H), 3.71 (AA′m, 4 H), 3.57

(BB′m, 4 H), 3.39 (s, 6 H).

¹³C NMR (100 MHz, CDCl₃):  = 159.3, 133.9, 114.7, 113.9, 81.1, 72.9,

71.8, 70.6, 69.5, 67.4, 58.9.

MS (FAB, 70 eV): m/z (%) = 438 ([M⁺]).

UV/VIS (MeCN): _max(log ) = 203 (4.74), 242 (sh, 4.28), 260 (sh, 4.41),

268 (4.47), 281 (4.50), 299 (4.56), 319 (4.65), 340 nm (3.54).

(6) For some recent reports featuring 6a and analogues as substitu-

ents, see: (a) Kang, S.; Lee, M.; Lee, D. J. Am. Chem. Soc. 2019,

141, 5980. (b) Hayashi, K.; Miyaoka, Y.; Ohishi, Y.; Uchida, T.;

Iwamura, M.; Nozaki, K.; Inouye, M. Chem. Eur. J. 2018, 24,

14613. (c) Ikai, T.; Yoshida, T.; Awata, S.; Wada, Y.; Maeda, K.;

Mizuno, M.; Swager, T. M. ACS Macro Lett. 2018, 7, 364. (d) Liu,

X.; Yuan, Y.; Bo, S.; Li, Y.; Yang, Z.; Zhou, X.; Chen, S.; Jiang, Z.-X.

Eur. J. Org. Chem. 2017, 4461. (e) Hayashi, K.; Inouye, M. Eur. J.

Org. Chem. 2017, 4334.

Funding Information

This work was enabled by the NSF (CHE 0907800).

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Acknowledgment

U.D. thanks the Alexander von Humboldt Foundation for a Feodor

Lynen Research Fellowship.

(7) For some recent reports featuring 6b and analogues as substitu-

ents, see: (a) Herkert, L.; Droste, J.; Kartha, K. K.; Korevaar, P. A.;

de Greef, T. F. A.; Hansen, M. R.; Fernández, G. Angew. Chem. Int.

Ed. 2019, 58, 11344. (b) Kasthuri, S.; Kumar, S.; Raviteja, S.;

Ramakrishna, B.; Maji, S.; Veeraiah, N.; Venkatramaiah, N. Appl.

Surf. Sci. 2019, 481, 1018. (c) Tang, S.-X.; Wang, N.; Xu, X.-D.;

Feng, S. New J. Chem. 2019, 43, 6461. (d) Lechner, B.-D.; Biehl, P.;

Ebert, H.; Werner, S.; Meister, A.; Hause, G.; Bacia, K.;

Tschierske, C.; Blume, A. J. Phys. Chem. B 2018, 122, 10861.

(e) Sagara, Y.; Seki, A.; Kim, Y.; Tamaoki, N. J. Mater. Chem. C

2018, 6, 8453. (f) Pan, D.; Zhong, X.; Zhao, W.; Yu, Z.; Yang, Z.;

Wang, D.; Cao, H.; He, W. Tetrahedron 2018, 74, 2677.

Supporting Information

Supporting information for this article is available online at

https://doi.org/10.1055/s-0039-1690050.

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Article Doi

Oligoether-Substituted Derivatives of Carbon-Rich 1,4,7,10,13,16-Hexaethynyltribenzo[a, e, i]cyclododeca-5,11,17-triyne (C 36 H 12) and 1,4,9,12-Tetrakis(ethynyl)dibenzo[a, g]cyclododeca-5,7,13,15-tetrayne (C 28 H 8): Potential Precursors to the Circular [6]Phenylene ('Antikekulene') Frame

DOI: 10.1055/s-0039-1690050

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