Synthesis, characterization, and solid-state polymerization of cross-conjugated octatetraynes

Article abstract of DOI:10.1139/v2012-075

Two series of cross-conjugated 1,3,5,7-octatetraynes (1a-1l and 6a-6d) have been synthesized. UV-vis spectroscopic analysis shows that pendent groups connected to the cross-conjugated skeleton have little effect on the λ_max energies, irrespective of whether the groups are electron withdrawing or donating. A number of the isolated products readily give crystals suitable for X-ray crystallography, and the solid-state structural properties of five derivatives (1k, 1l, 6a, 6c, and 6d) have been examined by X-ray crystallographic analysis. Parallel packing of the polyynes in the solid state indicates that four of the five samples are potentially suitable for topochemical polymerization, based on solid-state packing parameters θ, R, and d. Attempts to effect a solid-state reaction have been explored through UV-vis and γ-ray irradiation as well as thermal heating. The course of these reactions was monitored by differential scanning calorimetry (DSC) analysis, as well as UV-vis and solid-state ¹³C NMR spectroscopy (for 1d, 1j, 1k, and 6d), which offered evidence of polymer formation from these reactions. Structural determination of the product(s), however, remains elusive.

Full text of DOI:10.1139/v2012-075

994
Synthesis, characterization, and solid-state
polymerization of cross-conjugated octatetraynes
Yuming Zhao, Thanh Luu, Guy M. Bernard, Tyler Taerum, Robert McDonald,
Roderick E. Wasylishen, and Rik R. Tykwinski
Abstract: Two series of cross-conjugated 1,3,5,7-octatetraynes (1a–1l and 6a–6d) have been synthesized. UV–vis
spectroscopic analysis shows that pendent groups connected to the cross-conjugated skeleton have little effect on the ␭
max
energies, irrespective of whether the groups are electron withdrawing or donating. A number of the isolated products
readily give crystals suitable for X-ray crystallography, and the solid-state structural properties of five derivatives (1k, 1l,
6a, 6c, and 6d) have been examined by X-ray crystallographic analysis. Parallel packing of the polyynes in the solid state
indicates that four of the five samples are potentially suitable for topochemical polymerization, based on solid-state packing
parameters ␪, R, and d. Attempts to effect a solid-state reaction have been explored through UV–vis and ␥-ray irradiation
as well as thermal heating. The course of these reactions was monitored by differential scanning calorimetry (DSC)
analysis, as well as UV–vis and solid-state 13C NMR spectroscopy (for 1d, 1j, 1k, and 6d), which offered evidence of
polymer formation from these reactions. Structural determination of the product(s), however, remains elusive.
Key words: polytriacetylenes, polyynes, solid-state NMR spectroscopy, tetraynes, topochemical polymerization.
Résumé : On a réalisé la synthèse de deux séries de 1,3,5,7-octatétraynes a conjugaisons croisées (1a–1l et 6a–6d).
`
L’analyse de leurs spectres UV–visible montre que les groupes pendants attachés au squelette a conjugaison croisée n’ont
`
que peu d’effet sur les énergies des ␭max, que les groupes attachés soient électroaffinitaires ou électrorépulsifs. Un certain
nombre de produits isolés fournissent des cristaux susceptibles d’être soumis a une diffraction par des rayons-X; on a ainsi
`
pu déterminer les propriétés structurales de cinq dérivés (1k, 1l, 6a, 6c et 6d) par une analyse des données
cristallographiques par cette méthode. L’entassement parallèle des polyynes a l’état solide indique que quatre des cinq
`
échantillons pourraient éventuellement être susceptibles de donner lieu a une polymérisation topochimique si on se base sur
`
leurs paramètres d’empilement ␪, R et d. On a exploré la possibilité de réaliser des réactions a l’état solide par des
`
irradiations UV–visible et par des rayons ␥ ainsi que par un chauffage thermique. On a suivi le cours de ces réactions par
le biais d’une analyse par calorimétrie a balayage différentiel (CBD) ainsi que par les spectroscopies UV–visible et RMN
`
du 13C a l’état solide (pour les composés 1d, 1j, 1k et 6d) qui fournissent des données suggérant qu’il y a formation de
`
polymères au cours de ces réactions. La détermination des structures de ces produits demeure toutefois incertaine.
Mots-clés : polytriacétylènes, polyynes, spectroscopie RMN a l’état solide, tétraynes, polymérisation topochimique.
`
[Traduit par la Rédaction]
with unique solution-state properties.9–11 The topochemical
Introduction
polymerization of a “diacetylene” (diyne) monomer into a
polydiacetylene polymer was first reported by Wegner12 in
1969. In the intervening years, the breadth of this general
process has been studied and expanded. These investigations
have documented quite clearly that the solid-state packing of
the polyyne precursor in the crystalline state is crucial to
formation of the desired polymer.13–16 In polyyne crystals,
molecules must move cooperatively during the reaction pro-
cess to arrive at the ordered structure of the polymeric product
During the past couple of decades, solid-state polymeriza-
tion of polyynes has been the subject of considerable explo-
ration in the quest for conjugated organic materials with
qualities suitable for applications in nanoscience, nonlinear
optics, organic electronics, supramolecular chemistry, and
sensing.1–8 Solid-state polymerization of polyynes is an attrac-
tive route to such materials because it can provide large and
nearly defect-free polymer crystals, as well as materials
Received 17 February 2012. Accepted 28 June 2012. Published at www.nrcresearchpress.com/cjc on 30 November 2012.
Y. Zhao. Department of Chemistry Memorial University of Newfoundland, St. John’s, NL A1B 3X7, Canada.
T. Luu, G.M. Bernard, T. Taerum, and R.E. Wasylishen. Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2,
Canada.
R. McDonald. X-ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
R.R. Tykwinski. Department of Chemistry and Pharmacy & Interdisciplinary Center of Molecular Materials (ICMM), University of
Erlangen-Nuremberg, Henkestrasse 42, 91054 Erlangen, Germany.
Corresponding author: Rik R. Tykwinski (e-mail: rik.tykwinski@chemie.uni-erlangen.de).
Dedicated to Professor Derrick Clive in recognition of a lifetime of contributions to organic synthesis.
Can. J. Chem. 90: 994–1014 (2012)
doi:10.1139/v2012-075
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Zhao et al.
995
Fig. 1. Schematic crystal packing for several modes of octatetrayne polymerization, and optimal parameters ␪, R, and d for each addition
pattern. (a) Polytetraacetylene formation via 1,8-addition. (b) Polytriacetylene formation via 1,6-addition. (c) Polydiacetylene formation via
3,6-addition. (d) Ladder polymer formation via two sequential 1,4-additions.
(i.e., a phase transition). When the solid-state arrangement of
the polyyne precursors offers a reaction pathway with minimal
translational energy, a topochemical reaction is possible when
initiated by, for example, heat, UV light, pressure, or ␥-ray
radiation. Such reactions are common for diynes and selec-
tively form the polydiacetylene product. For longer polyyne
precursors, however, multiple reaction possibilities exist, as
schematically shown in Fig. 1 for tetraynes. Thus, while
polyyne precursors offer a tantalizing opportunity to form
highly conjugated polymer products,15,17,18 the various modes
of reactivity present a number of challenges, including the
realization of the single crystals with optimal packing param-
eters, dictating one particular reaction pathway to the exclu-
sion of another, and characterization of the often insoluble
reaction product(s).
Efforts to effect polymerization of polyynes beyond the
length of a diyne have been relatively rare, although several
examples are described for the polymerization of triynes,19
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Can. J. Chem. Vol. 90, 2012
Scheme 1. Synthesis of tetraynes 1a–1l. Reagents and conditions:
(a) PdCl2(PPh3)2, CuI, i-Pr2NH, THF, rt; (b) K2CO3, MeOH, THF;
(c) CuCl, TMEDA, acetone or acetone/CH2Cl2 (1:1), O2 (air), rt.
The longest linearly conjugated segment is highlighted in bold.
THF, tetrahydrofuran; TMEDA, tetramethylethylenediamine.
These reactions generally proceeded smoothly at room tem-
perature (rt) and were complete within 2 h. Isolated yields of
triynes 4a–4l were good to excellent, and, with the exception
of 4a (an oil), triynes 4 are isolated as stable solids. Protodesi-
lylation of 4a–4l then provided the terminal alkynes 5a–5l,
which were carried on directly, following workup, to the
oxidative homocoupling step using Cu-mediated Hay condi-
tions.30 The homocoupling reactions were typically complete
in ~0.5 h at rt using either acetone or a mixture of acetone/
CH2Cl2 (1:1) as solvent. Isolated yields for 1a–1l ranged from
excellent to poor, depending primarily on the stability of the
resulting product. Nitroaryl functionalized tetraynes 1e–1g
had particularly poor stability, even at low temperature and in
solution. This resulted in drastically reduced isolated yields for
1e and 1f, whereas 1g was insufficiently stable for isolation.
While n-butyl- and cyano-substituted tetraynes 1a and 1h,
respectively, were also relatively unstable at room tempera-
ture, yields were nevertheless reasonable and the products
could be handled without significant decomposition if kept in
solution.
Next, our investigations of ␣,␻-polyynes31 led to the for-
mation of the dibromoolefinic analog of tetrayne 1c, namely
6a (Scheme 2). Compound 6a was isolated as a crystalline
solid with interesting solid-state packing based on X-ray anal-
ysis (vide infra). This suggested a second class of octatetra-
ynes that might be explored for their solid-state behaviour.
Tetraynes 6a–6d were easily synthesized starting from com-
mercially available acid chlorides 7a–7d as shown in
Scheme 2 and summarized in Table 2. In the first step, a
Friedel–Craftsacylationreactionof7a–7dwith1,4-bis-trimeth-
ylsilyl-1,3-butadiyne (8) in the presence of AlCl3 afforded the
intermediate ketones 9a–9d, after quenching of the reaction
and aqueous workup.32 The crude ketones were then converted
directly to dibromoolefins 10a–10d via the Ramirez olefina-
tion reaction.33 Isolated yields were good to excellent over the
two steps, and 10a–10d were obtained as stable crystalline
solids. With diyne precursors 10a–10d in hand, desilylation
using K2CO3/MeOH gave the terminal alkynes, which were
carried on directly to Hay30 homocoupling in CH2Cl2. The
desired products (6a–6d) were isolated pure in good to mod-
erate yields by either column chromatography or recrystalli-
zation from hexanes.
pentaynes,20 and hexaynes.21 There has been slightly more
work done in the area of tetraynes,22 likely because of the fact
that tetraynes are both easy to synthesize and relatively stable
under ambient conditions.23 In considering the topochemical
polymerization of tetraynes, several pathways must be consid-
ered, as outlined in Fig. 1. In each case, packing parameters
based on the orientation of neighbouring molecules stacked
parallel in the solid state govern reactivity patterns that might
be energetically accessible. The packing parameters are de-
fined as (i) the stacking or translational distance of the mono-
mers in the parallel stack (d), (ii) the angle formed between the
polyyne and the stacking axis (the “tilt angle”; ␪), and (iii) the
distance between the reacting carbon atoms in neighbouring
molecules of the stack (R).13,15 For example, 1,8-addition for
a tetrayne gives a polytetraacetylene product (Fig. 1a),
whereas 1,6-addition forms a polytriacetylene24 product
(Fig. 1b). A variety of reaction pathways are possible that
would result in polydiacetylene formation via a formal 1,4-
addition pattern, such as those in Figs. 1c and 1d, which afford
interesting cross-conjugated polymers.25 It is noteworthy that
topochemical polymerization can also lead to polydiacetylene
“ladder polymers” through two sequential 1,4-polymerization
events (Fig. 1d).17b As part of an ongoing interest in the
structural and electronic properties of cross-conjugated enyne
systems,25a,26 we serendipitously discovered that a large num-
ber of cross-conjugated tetrayne products crystallize with the
polyynes stacked in parallel, with packing parameters poten-
tially suitable for topochemical polymerization. Thus, we re-
port herein on the synthesis and study of two series of
tetraynes, the spectroscopic characterization of these com-
pounds, our efforts to polymerize these polyynes, and diffi-
culties encountered in the characterization of the product(s) of
these solid-state reactions.
13C-labelling of compound 6d
It is well-established that solid-state 13C NMR spectroscopy
can provide invaluable structural information concerning the
products of topochemical polymerization reactions.34 With
this in mind, the synthesis of tetrayne 6d enriched with 13C
atoms was undertaken (Scheme 3). The synthesis began with
the known dibromoolefin 11,35 which incorporated ~34% 13C
at position C(1) (indicated with an *). The reaction of the
dibromoolefin 11 with excess lithium diisopropylamide (LDA)
at low temperature effected elimination, and the resulting
lithiated diyne product was trapped via the reaction with
Me3SiCl to give differentially silylated diyne 12.36 Following
a similar reaction sequence as outlined in Scheme 2, diyne 12
was then converted into ketone 13 via a Friedel–Crafts acyla-
tion with 7d, and the ketone was carried on directly to a
standard dibromoolefination reaction affording dibromoolefin
14 in a reasonable yield (35%) over the two steps. The pres-
ence of the triisopropylsilyl group in 14 necessitated the use of
Synthesis
Notably, the synthesis of the cross-conjugated tetrayne se-
ries 1a–1l is achieved in three efficient steps, as described in
Scheme 1 and summarized in Table 1.27 First, Pd-catalyzed
Sonogashira cross coupling28 of the known vinyl triflate 229
with various terminal acetylenes (3a–3l) gave enynes 4a–4l.
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Zhao et al.
997
Table 1. Synthetic details and selective physical properties of enetriyne precursors 4a–4l and tetraynes 1a–1l.
4
1
Description
Yield (%) (mp, °C)a
Description
Yield (%) (mp, °C)a
DSC, dp
(Tonset/Tmax; °C)
Entry
R
a
b
n-Butyl
98
65
Unstable oil
Colourless solid (54–57) 91
94
Unstable oil
Brown solid (57–62)
—
—
c
d
e
96
90
87
Colourless solid (71–72) 66
Yellow, waxy solid
Yellow solid
—
Yellow solid (94–95)
Yellow solid (93–94)
95
27
172/193
—
Unstable, yellow semisolid
f
91
36
Yellow solid (77–78)
Yellow solid (68–69)
39
0
Unstable, yellow semisolid
—
—
—
g
h
i
80
79
83
56
Yellow solid (60–62)
Colourless, waxy solid
Yellow solid (82–83)
Yellow solid (84–85)
74
85
76
75
Unstable, yellow solid
Yellow solid
—
123/131
157/165
160/187
j
Yellow solid
k
Orange solid
lb
i-Pr3Si
93
Colourless solid (30–31) 96
Yellow solid (103–104)
145
Note: mp: melting point, DSC: differential scanning calorimetry, dp: decomposition, T: temperature.
aMeasured in an open capillary tube.
bSynthesized as reported in ref. 27.
Scheme 2. Synthesis of tetraynes 6a–6d. Reagents and conditions:
(a) AlCl3, CH2Cl2, –20 °C; (b) CBr4, PPh3, CH2Cl2; (c) K2CO3,
MeOH/THF; (d) CuCl, TMEDA, CH2Cl2, O2 (air), rt. The longest
linearly conjugated segment is highlighted in bold. THF, tetrahy-
drofuran; TMEDA, tetramethylethylenediamine.
the partial labelling, three isotopomers were formed from the
homocoupling reaction, including compound 6d (no labelled
carbon), 6d* (one labelled carbon), and 6d** (two labelled
carbons). As expected, however, the 13C NMR spectrum of
this mixture is identical to that of the unlabelled compound
6d, except for the enhanced signal of the C(1) carbon of the
octayne chain and the associated 13C–13C coupling (vide
infra).
Solution-state 13C NMR spectroscopic
characterization
Solution-state 13C NMR spectroscopy of compounds 1a–1l
shows that the ␣ carbons of the isopropylidene backbone
(Me2CϭCϽ) are easily identified because they are quite
deshielded, resonating in the range of 160–165 ppm.37
Electron-withdrawing aryl groups result in a downfield shift of
this signal, such that the resonances of 1d (4-NO2–C6H4–), 1e
(2-NO2–C6H4–), 1f (3-NO2–C6H4–), and 1h (4-NC–C6H4–)
are found at 163.9, 165.0, 163.4, and 163.6 ppm, respectively.
Conversely, electron-donating groups result in a slight upfield
shift of this carbon resonance, as with derivatives 1j (4-NMe2–
tetrabutylammonium fluoride (TBAF) to effect desilylation,
and the thus formed terminal diyne was then subjected to
oxidative homocoupling under Hay conditions. As a result of
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Can. J. Chem. Vol. 90, 2012
Table 2. Synthetic details and selective physical properties of diyne monomers 10a–10d and tetraynes 6a–6d.
10
6
a
Entry
R
H
Yield (%) Description (mp, °C)
Yield (%) Description (dp, °C)a
DSC: mp/dp (°C); Tonset /Tmax (°C)
a
b
c
77
Colourless solid (85–87) 75
Yellow solid (185)
—; 191/192 (dp)
OMe 90
t-Bu
NO2
Off-white solid (72–74)
Yellow solid (96–98)
Off-white solid (80–83)
46
80
51
Yellow-green solid (168–170) 176 (mp); 176/179 (dp)
65
51
Yellow solid (168–179)b
190;c 230/233 (dp)
—; 189/191 (dp)
d
Yellow solid (ϳ190)
Note: mp: melting point, dp: decomposition, DSC: differential scanning calorimetry, T: temperature.
aMeasured in an open capillary tube.
bApparent melting point.
cWeak exotherm.
Scheme 3. Synthesis of isotopomers 6d/6d*/6d**. Reagents and
conditions: (a) LDA, THF, –78 °C, then Me3SiCl, 67%; (b) 7d,
AlCl3, CH2Cl2, –20 °C; (c) CBr4, PPh3, CH2Cl2, 0 °C, 35% (from 12);
(d) TBAF, THF, rt; (e) CuCl, TMEDA, CH2Cl2, O2, rt, 42% (from
14). LDA, lithium diisopropylamide; THF, tetrahydrofuran; TBAF,
tetra-n-butylammonium fluoride; TMEDA, tetramethylethyl-
enediamine.
the case of 1a–1l, this places C(3) and C(4) at either ~64 or
68 ppm, regardless of the substitution pattern. The adjacent
carbons C(1) and C(2), on the other hand, resonate in the range
of 74–77 ppm. A similar pattern is found for 6a–6d, where
labelling of 6d*/6d** provides an opportunity to identify each
specific carbon within this tetrayne series. The labelled carbon
C(1) for 6d*/6d** is observed at 75.6 ppm, and the large cou-
pling with C(2) at ␦ 82.7 (1J(13C, 13C) ϭ 187 Hz) sets this carbon
resonance. Coupling between C(1) and C(3) at 71.4 ppm is also
2
clearly observed with J(13C, 13C) ϭ 32 Hz, and C(4) is thus
identified as the remaining resonance at 64.9 ppm.
Solution-state UV–vis spectroscopic
characterization
Highest occupied and lowest unoccupied molecular orbital
(HOMO–LUMO) transitions for 1a–1l and 6a–6d should re-
sult from the longest linearly conjugated segment of these
molecules (the ene–tetrayne–ene group highlighted in bold,
Schemes 1 and 2).27 In 1a–1l, there is a progression of three
absorptions at approximately 350, 375, and 405 nm (Fig. 2a).
The various pendent functional groups have a negligible effect
on the energy of these transitions as a result of the cross-
conjugated framework.25–27,42 The most distinguishing effect
based on structure is observed for derivatives with strong
electron withdrawing and donating substituents, 1d and 1j,
respectively, where an enhancement in molar absorptivity is
observed in comparison with other derivatives. For the organo-
metallic member of the series (1k), a weak, broad peak at
450 nm is attributed to the absorption characteristic of the
ferrocenyl groups.
All members of the second series of tetraynes 6a–6d also
display three peaks in the low-energy region of the spectra at
~359, 387, and 419 nm (Fig. 2b). In addition, all four com-
pounds have similar molar absorptivity values (ε). Thus, for
6a–6d, as observed for 1a–1l, varying the pendent substituents
does not appreciably influence the wavelength of maximum
absorption (␭max) values.
C6H4–) and 1k (ferrocenyl) at 159.5 and 159.9 ppm, respec-
tively. The analogous carbons for tetraynes 6a–6d, terminated
with a dibromovinyl group (Br2CϭCϽ), are found at much
lower chemical shift values, a result of the heavy atom effect,
typically in the range of ~100 ppm based on published studies
using 13C labelling.38 This places the resonance in the region
of the alkyne carbon signals and complicates unambiguous
assignment for 6a–6d. Empirically, however, signals observed
for 6a–6d (and 10a–10d) in the range of 102–108 ppm are
consistent with this assignment. Conversely, the ␤-alkylidene
carbons (Me2CϭCϽ) for isopropylidene compounds such 1a–1l
are typically found in the range of 99–100 ppm,37 and thus they
are also difficult to conclusively discern from the alkyne carbon
resonances. For compounds 6d and 14, the ␤-alkylidene carbon
(Br2CϭCϽ) can be identified at 127.6 and 128.3 ppm, respec-
tively, as a result of the large one-bond coupling (1J(13C, 13C) ϭ
98 Hz) in each case to the 13C-labelled carbon at C(1). This
Solid-state properties and attempted
topochemical polymerization
Looking at the kinetic and thermal stability of cross-
conjugated tetraynes 1a–1l and 6a–6d, derivatives with
4-nitrophenyl (1d), 4-N,N-dimethylaminophenyl (1j), ferrocenyl
(1k), and triisopropylsilyl (1l) substituents show sufficient
stability for detailed study, as do all four compounds 6a–6d.
As described in the following sections, our studies to date
1
compares to one-bond J(13C, 13C) values of 34.6, 67.6, and
171.5 Hz for ethane, ethylene, and acetylene, respectively.39
Generally, the resonances of carbons C(3) and C(4) of an
octatetrayne moiety (–C(1)ϵC(2)–C(3)ϵC(4)–CϵC–CϵC–)
are found upfield relative to those of C(1) and C(2).35,40,41 In
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Zhao et al.
999
Fig. 2. Electronic absorption spectra (ε, L mol–1 cm–1) for (a) 1c,
1d, 1j, and 1k in CHCl3 and (b) 6a–6d in THF.
Fig. 3. Solid-state 13C NMR spectra for 1d recorded (a) before
heating and (b) after heating at 120 °C for 2 h and then 160 °C for
1 h.
Tetrayne 1d
The DSC profile of 1d shows a relatively broad and fea-
tureless Gaussian-shaped peak at 193 °C (see the Supplemen-
tary data), which suggests that the polymerization probably
occurs in a random, nonregioselective manner. This premise
has been examined by solid-state 13C NMR spectroscopy. The
spectrum of pristine 1d (Fig. 3a) shows moderate resolution,
and major signals for the sp and sp2 carbons in the region of
64–100 ppm are reasonably consistent with solution-state 13
C
NMR data. In addition to the expected resonances, however,
several unidentified peaks are observed, likely the result of
nonequivalent carbon atoms in the solid state (from a structure
where C2 symmetry has been lost). The same is true for the
resonance of the external vinylidene carbon (Me2CϭC), which
is observed at 164 ppm in addition to two additional signals at
a similar chemical shift. After heating the sample of 1d at
120 °C for 2 h, the resulting 13C NMR spectrum is identical to
that of the original, indicating that polymerization had not
occurred at this temperature. Subsequent heating at 160 °C for
1 h, on the other hand, gives a black solid. The spectrum of this
product shows that the characteristic resonances for interior
tetrayne carbons at 64–67 ppm are completely gone after
heating (Fig. 3b). While in agreement with a polymerized
product, the loss of acetylenic signals coincides with the
appearance of several broadened resonances in the region of
100–160 ppm, presumably the result of sp2 carbons of olefinic
and aryl moieties. In addition, the resonances of the methyl
groups are also broadened significantly to a range of 15–
30 ppm. The transition to broad featureless resonances, along
with the absence of signals from sp carbon atoms, suggests
that a random and nonregioselective polymerization occurs for
this sample upon heating.
include differential scanning calorimetry (DSC) analysis for
all eight of these compounds, X-ray crystallographic analysis
of 1k, 1l, 6a, 6c, and 6d, and solid-state 13C NMR spectro-
scopic analysis of 1d, 1j, 1k, and 6d during attempts to effect
topochemical polymerization.
Last but not least, it is useful to point out several common
threads from this study, as a prelude to the specific discussions
that follow. Many reports for the solid-state reaction of
polyynes have underscored the fact that the most important
criteria for effective topochemical polymerization are the
solid-state packing parameters ␪, R, and d as summarized in
Fig. 1. Supplemented with DSC analysis, this information
offers, a priori, a guide for the selection of crystalline candi-
dates for further study. It will become clear in the following
sections, however, that a combination of suitable packing
parameters and “sharp” DSC traces are only a part of the story
for polymerization of tetraynes. As the solid-state 13C NMR
spectroscopic studies eventually demonstrate, each “promising
prospect” for thermal polymerization to a defined product
results in only ambiguous evidence of the nature of the prod-
uct, regardless of how “optimal” the packing parameters.
Tetrayne 1j
The DSC trace of 1j shows a sharp exotherm at 165 °C (see
the Supplementary data), suggesting that a solid-state reaction
may be more regioselective than that observed for 1d. In the
absence of crystallographic data, the reaction has been ex-
plored by solid-state 13C NMR spectroscopy. The spectrum of
1j at room temperature (Fig. 4a) shows reasonable resolution
when compared to the solution-state 13C NMR spectrum. All
eight unique sp and sp2 carbons of the cross-conjugated enyne
skeleton are clearly observed at 65, 68, 77, 82, 98, 102, 106,
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Can. J. Chem. Vol. 90, 2012
Fig. 4. Solid-state 13C NMR spectra for 1j recorded (a) before
heating (time ϭ 0), (b) after heating at 100 °C for 60 min, and
(c) after heating at 100 °C for 255 min.
of 0.056(3) Å from a least-squares plane (Fig. 5). All triple
bonds are comparable to other reported tetraynes (Table 3).13
The carbons of the tetrayne framework show a gradual curva-
ture with bond angles deviating from 180° by less than 4° in
all cases (Table 4). The plane of the cyclopentadienyl ligand
for the ferrocene group is, nevertheless, twisted out of the
enyne plane by an angle of ~31°.
The most notable feature of the solid-state structure of 1k is
the parallel stacking of tetrayne moieties, suggesting the pos-
sibility of a topochemical polymerization. In the solid-state
packing of 1k, molecules show a tilt angle (␪) of 30° and the
translational distance (d) is 7.4 Å. There are two potential
modes for 1,6-polymerization, with R1,6 ϭ R3,8 ϭ 3.7 Å. Thus,
these features correspond quite well with the optimal param-
eters of ␪ ϭ 28°, R1,6 Ͻ 4 Å, and d ϭ 7.4 Å for topochemical
polymerization in a 1,6-addition manner.
With a viable crystal seemingly in hand for effecting 1,6-
polymerization, several approaches have been explored. Po-
lymerization via UV irradiation (monochromic 280 nm for
12 h) fails to induce polymerization, and crystals show a
diffraction pattern identical to the original tetrayne sample.
Likewise, ␥-ray irradiation (60Co, 54 Ϯ 3 krad/h for 2 weeks)
also fails to initiate polymerization. Attempts to induce a
thermal reaction show that when heated to 150 °C for 30 min,
crystals of 1k transform into a black solid, suggesting that
topochemical polymerization of 1k can be effected through
heating. The resulting solid is, however, amorphous rather
than crystalline, as established by X-ray crystallographic
analysis.
UV–vis spectroscopy was used to analyze the thermal po-
lymerization of 1k in a solid film cast onto a quartz plate.
Three characteristic absorptions are observed for 1k at 354,
381, and 414 nm, and these absorptions are redshifted by
5–7 nm for 1k versus those measured in CHCl3 (Fig. 6). After
heating the sample open to air at 150 °C for 5 min, the UV–vis
spectrum clearly shows loss of the low-energy absorptions
ascribed to the ene–tetrayne–ene moiety, and these signals are
replaced by a broad featureless peak at 400–550 nm. Disap-
pointingly, the lack of specific fine structure in the spectrum of
the product offers little hint as to the structure(s) resulting
from polymerization.
and 160 ppm, while the two methyl carbons of the isopro-
pylidene moiety are also distinct at 23 and 25 ppm. Finally, the
N,N-dimethylanilino carbons are observed at 40 ppm. After
heating at 100 °C for 1 h, the crystalline sample turns dark
brown, and the 13C NMR spectrum shows several distinct
differences with fair resolution (Fig. 4b). The most significant
changes upon heating are (i) the emergence of two nonequiva-
lent vinylidene peaks at 159 and 165 ppm, (ii) splitting of the
signal at 130 ppm, and (iii) several additional resonances in
the range of 90–110 ppm. The characteristic resonances of the
carbons of the polyyne fragment have approximately the same
chemical shift values (in the region of 60–85 ppm), but they
are broadened. Additional heating at 100 °C for ~3 h yields a
black solid, the spectrum of which shows severely broadened
signals, centred at 20, 40, 110, 130, and 150 ppm (Fig. 4c),
although many of the major features observed in the initial
spectrum after 60 min (Fig. 4b) are still distinguishable. In
combination, these spectra suggest that polymerization may
proceed in a regioselective manner, since distinct chemical
shifts are still observed for the product (i.e., Fig. 4c). Several
points deserve further discussion. If the reaction occurs via
1,6-addition, C2 symmetry of the starting tetrayne would be
destroyed while generating a polytriacetylene (PTA) product.
The upfield signals at 60–70 ppm are not, however, consistent
with the presence of a diyne group of a PTA. Alternatively,
reaction via 1,8-addition would afford a polytetraacetylene
product (Fig. 1a), and resonances in the ranges of 60–70 ppm
could be consistent with the formation of an unsymmetrical
triyne moiety.43 Unfortunately, without crystallographic data
of the starting material or product, more definitive conclusions
are difficult to draw.
Following the results of the UV–vis study, thermally initi-
ated polymerization of a crystalline sample of 1k was explored
by heating to 150 °C under air. Attempts to analyze the
1
polymerization product by solution-state H and 13C NMR
spectroscopy did not, however, afford meaningful spectra be-
cause the sample is not soluble in typical organic solvents.
Finally, the thermal polymerization for 1k was monitored by
solid-state 13C NMR spectroscopy, while the sample was
heated at 150 °C, and spectra were acquired over a period of
5 h (Fig. 7). The solid-state spectrum of the pristine tetrayne
1k shows excellent resolution in comparison with the solution-
state spectrum, and all unique sp and sp2 carbons of the
conjugated skeleton are clearly identified. As the sample is
heated, the spectra show gradual peak broadening that in-
creases with heating time. After heating the sample for
300 min, the spectrum is dominated by three broad signals
centered at approximately 30, 75, and 142 ppm. The most
intense, at ␦ 75 ppm, seemingly derives from the carbons of
the ferrocenyl group (the isotropic 13C chemical shift for solid
ferrocene is 70 ppm44), and this broad signal engulfs the
Tetrayne 1k
For ferrocenyl-substituted 1k, an exotherm is found at
~187 °C in the DSC analysis, and a shoulder peak is also
noticeable at slightly lower temperature (165 °C; see the
Supplementary data). Compound 1k is remarkably crystalline,
and orange-brown translucent needle-shaped crystals of 1k
suitable for X-ray crystallography are obtained easily by dif-
fusion of methanol into an Et2O solution at –4 °C. The
solid-state structure shows that the 16-carbon C2v symmetrical
enyne skeleton is virtually planar with a maximum deviation
Published by NRC Research Press

Zhao et al.
1001
Fig. 5. ORTEP) drawing (50% probability level) of 1k showing a segment of crystal packing. Geometry parameters: ␪ ϭ 30°, R1,6 ϭ 3.7 Å,
3,8 ϭ 3.7 Å, and d ϭ 7.4 Å. (Note: The numbering of the carbon chain corresponds to the structural characterization listed in Tables 3 and 4,
R
whereas the numbering for R1,6 and R3,8 refers to reactivity patterns from Fig. 1.)
Table 3. Selected bond lengths for tetraynes 1k, 1l, 6a, 6c, and 6d.
Bond length (Å)
Product
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
1k
1l
6a
6c
6d
1.185(5)
1.200(3)
1.207(4)
1.207(4)
1.204(4)
1.383(6)
1.369(3)
1.364(4)
1.365(4)
1.363(4)
1.211(5)
1.209(3)
1.199(4)
1.203(4)
1.204(5)
1.355(8)a
1.365(3)
1.361(5)
1.371(6)a
1.357(7)a
1.203(3)
1.211(4)
1.373(3)
1.357(4)
1.200(3)
1.207(4)
aC(4)—C(4=).
Table 4. Selected bond angles for tetraynes 1k, 1l, 6a, 6c, and 6d.
Bond angle (°)
C(10)–C(9)– C(9)–C(1)– C(1)–C(2)– C(2)–C(3)– C(3)–C(4)– C(4)–C(5)– C(5)–C(6)– C(6)–C(7)– C(7)–C(8)– C(8)–C(11)–
Product C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(11)
C(12)
1k
1l
6a
6c
6d
121.3(4)a
121.95(18) 179.1(2)
119.5(3)
120.9(3)a
120.2(3)a
178.9(5)b
176.6(5)
177.8(2)
179.0(4)
178.3(3)
179.1(4)
177.1(5)
177.5(2)
179.4(4)
178.5(3)
177.1(4)
177.5(6)c
179.4(2)
179.3(4)
179.6(4)c
179.8(6)c
179.5(3)
179.8(4)
178.1(2)
179.7(4)
177.1(2)
177.8(4)
178.2(2)
176.8(4)
121.22(18)
118.3(3)
177.4(4)
175.9(3)b
174.3(4)b
aC(6)–C(5)–C(1).
bC(5)–C(1)–C(2).
cC(3)–C(4)–C(4=).
region where polyyne signals are expected, making any par-
ticular assignments impossible. The signal at the highest
chemical shift is very broad, spanning from 120–160 ppm, and
probably results from sp2 carbons of the vinylidene carbons
and olefinic carbons formed during polymerization, or both. A
background signal from the probe is also expected to contrib-
ute signal to this region. Thus, in comparison with 1j, there is
little clear evidence that 1k polymerizes through a regioselec-
tive process, i.e., 1,6-addition, as suggested by its crystallo-
graphic analysis.
Tetrayne 1l
DSC analysis of crystalline 1l shows a well-defined melting
point at 103–104 °C, which is then followed by decomposition
of the sample at 145 °C (see the Supplementary data). Yellow
single crystals of tetrayne 1l are obtained by diffusion of
MeOH into a CH2Cl2 solution at –20 °C. Surprisingly, two
different polymorphs of 1l could be obtained from seemingly
identical crystallization conditions. In addition, there appears
to be no way to direct which polymorph will result for a given
crystallization attempt. Both solid-state structures adopt geo-
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1002
Can. J. Chem. Vol. 90, 2012
Fig. 6. Solid-state UV–vis spectra for 1k before and after heating
the thin-film sample to 150 °C for 5 min.
close contacts are also in a favourable range, R1,6 ϭ 3.7 Å and
R3,8 ϭ 3.6 Å.
In spite of the favourable packing parameters observed for
1l, all efforts to effect the thermal polymerization of single
crystals for this tetrayne have been unsuccessful. Heating a
sample of 1l at 90 °C (i.e., just below the melting point) for 8 h
gives a sample that is slightly darkened to yield an opaque
solid that is no longer crystalline as documented by the ab-
sence of an X-ray diffraction pattern. Other methods to initiate
the polymerization have also been explored, including mono-
chromatic UV irradiation (280 nm for 24 h) and ␥-irradiation
(54 Ϯ 3 krad/h for 2 weeks). In both cases, darkened yellow-
orange single crystals are produced. X-ray analysis of these
crystals, however, reveals exactly the same diffraction pattern
as found for pristine 1l, and there appears to be little change in
the solid beyond a possible reaction at the outer surface of the
crystal. Thus, there is so far no efficient way to trigger a
solid-state polymerization in single crystals of 1l.
Tetrayne 6a
DSC analysis of tetrayne derivative 6a shows a sharp, narrow
exotherm at 192 °C, which is consistent with the possibility of a
reasonably well-defined topochemical polymerization (see the
Supplementary data). Compound 6a affords crystals for X-ray
crystallography from a mixture of hexanes and CH2Cl2. The
solid-state structure (Fig. 9 and Tables 3 and 4) shows that
neighbouring molecules align in stacks as centrosymmetric
dimeric pairs, thus giving an alternating A–B–A–B pattern.
This is most easily identified in Fig. 9 by the different twist
angles of the phenyl rings, which rotate out of the planar enyne
framework by ~56° and 43°. The C–CϵC angles of 6a deviate
slightly from linearity, but by no more than about 3° (Table 4),
whereas the torsion angle generated from vinyl groups (C10–
C9···C11–C12) is ~3°.
Fig. 7. Solid-state 13C NMR spectra for 1k recorded before and
after heating at 150 °C for the times shown.
Analysis of the solid-state packing parameters shows that
the tetrayne groups of neighbouring molecules are aligned
with ␪ ϭ 42°, R1,4 ϭ R3,6 ϭ R5,8 ϭ 3.4 Å, and d ϭ 5.1 Å.
Thus, whereas 1,6-polymerization is not possible (R1,6
ϭ
4.3 Å), the observed packing values are quite close to the
optimal values for 1,4-polymerization (␪ ϭ 45°, R1,4 Ͻ 4 Å,
and d ϭ 5.1 Å). Combined with the intense and sharp exo-
therm in the DSC measurement, it seems possible that com-
pound 6a might undergo a 1,4-topochemical polymerization
reaction. Because of our focus on 1,6-polymerization pro-
cesses, however, further studies on 6a have not yet been
conducted.
metrically similar s-trans orientations with respect to the
octatetrayndiyl moiety (as shown in Fig. 8).27 For one struc-
ture, molecules are aligned in parallel stacks, such that topo-
chemical polymerization might be possible (this structure is
shown in Fig. 8). The ␲ framework of 1l in this polymorph is
virtually planar, with a maximum deviation of 0.02 Å from a
least-squares plane for the 16 carbons of the conjugated skel-
etons. Triple bonds are unremarkable and comparable to other
reported polyynes of this length (Table 3).13,45 The eight
tetrayne carbons show only a slight curvature with bond angles
deviating from linear by less than 3° in all cases (Table 4).
Crystal packing analysis of tetrayne 1l shows that the indi-
vidual molecules are aligned in a parallel fashion that is
predicted to favour the 1,6-addition polymerization (Fig. 8).
The packing parameters of ␪ ϭ 28° and d ϭ 7.7 Å correspond
quite well to those required for 1,6-polymerization, while two
Tetrayne 6b
The DSC spectrum of tetrayne 6b shows a sharp endotherm
at ~176 °C, immediately followed by a broad exotherm at
179 °C (see the Supplementary data). No melting point is,
however, observed in a capillary melting point analysis. Thus,
it is not clear if the initial endotherm observed by DSC is a
phase transition or a true melting point. In any case, this
behaviour suggests that product analysis from a thermal solid-
state reaction would not be straightforward, so no further
analysis of this compound has been pursued.
Tetrayne 6c
Compound 6c shows an apparent melting point of 168–
170 °C in a capillary melting point analysis, and the sample
slowly darkens as the temperature is increased. DSC analysis,
Published by NRC Research Press

Zhao et al.
1003
Fig. 8. ORTEP drawing (50% probability level) of 1l showing a segment of crystal packing. Geometry parameters: ␪ ϭ 28°, R1,6 ϭ 3.7 Å,
R3,8 ϭ 3.6 Å, and d ϭ 7.7 Å. (Note: The numbering of the carbon chain corresponds to the structural characterization listed in Tables 3
and 4, whereas the numbering for R1,6 and R3,8 refers to reactivity patterns from Fig. 1.)
Fig. 9. ORTEP drawing (50% probability level) of 6a showing a segment of the crystal packing. Geometry parameters: ␪ ϭ 42°, R1,4
ϭ
3.4 Å, R3,6 ϭ 3.4 Å, R5,8 ϭ 3.4 Å, and d ϭ 5.1 Å. (Note: The numbering of the carbon chain corresponds to the structural characterization
listed in Tables 3 and 4, whereas the numbering for R1,4, R3,6, and R5,8 refers to reactivity patterns from Fig. 1.)
on the other hand, shows an initial broad, weak exotherm with
an onset at about 190 °C, and a second, sharp exotherm that
initiates at about 230 °C, with a maximum at 233 °C (see the
Supplementary data).
1,6-polymerization, and thermal analysis of this compound has
not been further explored.
Tetrayne 6d
DSC analysis of the nitro-derivative 6d shows a very sharp
exotherm at 191 °C (Tonset ϭ 189 °C and Tmax ϭ 191 °C, see
the Supplementary data). Warning: An explosion occurred at
approximately 190 °C when heating a small quantity of com-
pound 6d (60 mg) in a capped tightly packed solid-state NMR
rotor. When handling any polyyne, one should always take the
appropriate safety precautions when the sample is heated
above room temperature. This is particularly true if the sample
is a terminal polyyne, where precautions should be taken at all
temperatures.
X-ray quality crystals of 6c were obtained via the diffusion
of hexanes into a solution of 6c in hexanes/CH2Cl2 at –4 °C.
The solid-state structure of 6c (Fig. 10 and Tables 3 and 4)
reveals that the terminal acetylene angles C(5)–C(1)–C(2) are
the most distorted at 175.9(3)°. The enyne framework of the
centrosymmetric structure is completely planar, whereas the
aryl rings twist significantly from this plane by 65°. Analysis
of the crystal packing shows that neighbouring molecules of
compound 6c are aligned in a parallel fashion, and the packing
parameters for 6c are similar to that observed for 6a, with ␪ ϭ
38°, R1,4 ϭ 3.8 Å, R3,6 ϭ 3.7 Å, R5,8 ϭ 3.8 Å, and d ϭ 5.9 Å.
Thus, packing parameters are suboptimal for either 1,4- or
Single crystals of 6d for analysis by X-ray crystallography
were obtained via the evaporation of a CDCl3 or CHCl3
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1004
Can. J. Chem. Vol. 90, 2012
Fig. 10. ORTEP drawing (50% probability level) of 6c showing a segment of the crystal packing. Geometry parameters: ␪ ϭ 38°, R1,4
ϭ
3.8 Å, R3,6 ϭ 3.7 Å, R5,8 ϭ 3.8 Å, and d ϭ 5.9 Å. (Note: The numbering of the carbon chain corresponds to the structural characterization
listed in Tables 3 and 4, whereas the numbering for R1,4, R3,6, and R5,8 refers to reactivity patterns from Fig. 1.)
Fig. 11. ORTEP drawing (50% probability level) of 6d showing a segment of crystal packing. Geometry parameters: ␪ ϭ 29°, R1,6 ϭ 3.5
Å, R3,8 ϭ 3.5 Å, and d ϭ 7.5 Å. (Note: The numbering of the carbon chain corresponds to the structural characterization listed in Tables 3
and 4, whereas the numbering for R1,6 and R3,8 refers to reactivity patterns from Fig. 1.)
solution at –4 °C (Fig. 11). As with 6a and 6c (Table 4), the
terminal C(5)–C(1)–C(2) bond angle of 6d is the most dis-
torted from linearity at 174.3(4)°, and the centrosymmetric
enyne framework is planar. Molecules of compound 6d are
packed in parallel stacks, and the distance separating reactive
atoms of adjacent molecules is R1,6 ϭ R3,8 ϭ 3.5 Å. The
translational distance (d) is 7.5 Å, with a packing angle (␪)
of 29°. These values are thus ideal for a 1,6-topochemical
polymerization.
The UV–vis absorption spectrum of compound 6d has been
measured in the solid state (Fig. 12) for a thin film produced by
casting a solution of compound 6d in CH2Cl2 onto a quartz slide
and allowing the solvent to evaporate. The UV–vis spectrum of
the film shows absorbance values of 368, 400, and 434 nm, which
are somewhat red-shifted from those for the sample in solution
(359, 384, and 419 nm in THF). As the thin film is then heated at
170 °C under an argon atmosphere for 17 h, UV–vis absorption
spectra have been examined at various time intervals (Fig. 12).
After heating for 1 h, the intensity of the three low-energy
absorbances decreases, and ␭
values are slightly blue-shifted
max
to 365, 397, and 430 nm. After heating for 5 h, only two distinct
signals remain in the low-energy region at ~393 and 424 nm, and
these two signals finally merge into one broad signal after heating
for a total of 17 h. Rather surprisingly, this analysis implies that
the conjugated ene–tetrayne–ene framework is transformed into a
less conjugated product, rather than one with extended conjuga-
tion as would be expected upon formation of a polytriacetylene
product (Fig. 13).
Published by NRC Research Press

Zhao et al.
1005
Fig. 14. Solid-state 13C NMR spectra of compound 6d (a) before
Fig. 12. Solid-state UV–vis spectra for compound 6d before and
after heating at 170 °C for the times given.
heating and (b) after heating at 170 °C for 6 h under argon.
Fig. 13. Idealized structure resulting from 1,6-polymerization of
6d or labelled 6d/6d*/6d** (* indicates 13C atoms).
Thermal polymerization of 6d has been explored by heating
a crystalline sample to 170 °C under argon (see the previous
warning for compound 6d). Attempts to analyze the resulting
sample by solution-state 1H and 13C NMR spectroscopy show
that the resulting polymer is insoluble, and useful spectra
could not be obtained. Solid-state 13C NMR spectroscopy has
therefore been used to explore the thermal transformation of
6d (Fig. 14). In the pristine sample, four aromatic and two
alkenyl signals are observed in region 1 (Fig. 14, 120–
150 ppm). These resonances are found at similar chemical
shifts as in solution, except for the ␣-vinyl signal (Br2CϭCϽ),
which appears downfield from its solution value of 107.5 ppm.
The alkynyl peaks appear in region 2 (Fig. 14, 60–90 ppm),
and chemical shifts for the four distinct signals (67, 73, 79, and
84 ppm) correlate well with those found in the solution-state
spectrum at 64.8, 71.2, 75.9, and 82.6 ppm. After heating the
solid at 170 °C under an Ar atmosphere for 6 h, both downfield
signals in region 1 (Fig. 14, 142 and 147 ppm) appear to split
into two signals, while the remaining two signals in region 1
broaden somewhat. Signals in region 2 follow a similar pat-
tern, where two signals (79 and 84 ppm) seemingly split and
those at 67 and 73 ppm broaden slightly. Furthermore, the
intensity of all alkyne signals in region 2 decreases noticeably
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1006
Can. J. Chem. Vol. 90, 2012
Fig. 15. Solid-state 13C NMR spectra for compound 6d/6d*/6d**.
(a) Before heating. (b) After heating (sb, spinning side band; *,
labelled 13C signal). Spectra were acquired at 11.75 T (125 MHz
for 13C) using CP/MAS and a spinning frequency of 8 kHz.
Spectra acquired at various spinning frequencies (not shown)
confirmed that the peaks in the 100–150 ppm region in (a) arise
primarily from spinning sidebands.
Conclusions
We have described the synthesis of functionalized, cross-
conjugated tetraynes. UV–vis spectroscopic analysis shows
that the electronic characteristics of the tetrayne moiety dom-
inate the lower energy absorption region, and the side groups,
either electron-donating or electron-withdrawing, have only a
marginal influence on the absorption energy of the central
tetrayne chromophore. The solid-state structural properties of
five derivatives have been examined by X-ray crystallographic
analysis. Examination of the crystal structures with an eye
toward inducing solid-state reactions shows that the packing
parameters (␪, R, and d) for all but 6c fall within a range
suitable for topochemical polymerization, and the values for
three (1k, 1l, and 6d) are quite close to the values ideal for a
1,6-polymerization. To our knowledge, this is the first series of
structurally similar tetraynes that shows a consistent packing
motif conducive to topochemical polymerization. In addition
to X-ray crystallography, DSC analysis also supports the pros-
pect of a viable polymerization reaction toward a defined
product in many cases. Thus, the polymerization of tetraynes
has been explored using thermal, photochemical, and (or)
␥-irradiation for initiation. Furthermore, the thermally induced
solid-state reaction of 1d, 1j, 1k, and 6d has been studied in
more detail via solid-state 13C NMR spectroscopy. In all cases,
however, it has been frustratingly difficult to ascertain the
structure of the product, often owing to broadening of the
observed resonances in the 13C spectra, presumably because of
a regiorandom polymerization reaction.
Our inability to effect clean polymerization of these crys-
tallized samples is the most significant outcome of this study.
A survey of reports for topochemical polymerization of diynes
shows that there is typically a good correlation between
packing parameters and successful polymerization to a
polydiacetylene product. Combined with reports of success-
ful polymerization of polyynes as described in the Introduc-
tion, this leads to the naïve assumption that the controlled
polymerization of polyynes might also be predicted based on
solid-state packing. But the story is not so simple, and it is now
quite obvious to conclude that the successful polymerization
of tetraynes is far more complex than a simple analysis of
solid-state packing parameters ␪, R, and d.
relative to those in region 1. The spectral changes in regions 1
and 2 for the spectrum acquired after heating suggest a loss of
molecular symmetry, which is evidence for polymerization as
shown for the idealized transformation outlined in Fig. 13.
Unfortunately, it is once again not clear if the reaction pro-
ceeds via a 1,6-addition process as suggested by X-ray crys-
tallographic analysis or via an alternative pathway.
Crystals of partially labelled tetrayne sample 6d/6d*/6d**
could be obtained, but unfortunately only on a small scale,
giving a total sample amount of ~1 mg. X-ray crystallography
has established that the solid-state geometric packing of this
sample is identical to that of unlabelled 6d. A solid-state
13C NMR spectrum of 6d/6d*/6d** was acquired at 11.75 T
(125 MHz for 13C) using cross-polarization/magic-angle spin-
ning (CP/MAS) and a spinning frequency of 8 kHz (Fig. 15).
In the pristine sample, two strong signals are observed at 75.4
and 81.5 ppm owing to the presence of 13C labelling. This is
surprising given that the solid-state structure of 6d is expected
to be centrosymmetric based on the crystallographic analysis,
and only a single resonance for the labelled carbon is observed
in solution (75.6 ppm; see the Supplementary data). The origin
of the second signal is, at present, unexplained. Unfortunately,
spinning side bands are also quite intense. After heating the
sample holder containing compound 6d/6d*/6d** at 170 °C
under Ar for 3 days, the resulting spectrum shows the en-
hanced 13C signals at ~130 and 142 ppm, characteristic of
sp2-hybridized carbon atoms. At first sight, this result is in-
consistent with the analysis of unlabelled 6d for which alkyne
signals are still observed after heating (Fig. 14). It is likely,
however, that the extended heating time for 6d/6d*/6d** at
170 °C (3 days) versus that of 6d (6 h) results in additional
and nonselective reactions, ultimately giving a material
composed primarily of sp2-hybridized carbon. Thus, com-
pound 6d/6d*/6d** may undergo a 1,6-topochemical po-
lymerization, but the structure of the final product,
frustratingly, remains unsolved.
Experimental section
Irradiation with 60Co
Single crystals of either 4k or 4l were placed into a glass
vial and subjected to the irradiation from a 60Co source
(~54 Ϯ 3 krad/h, previously located at the Chemistry Depart-
ment, University of Alberta, Edmonton, Alberta) for 2 weeks
at room temperature. After irradiation, the colours of the
crystals became slightly darker and the crystals were re-
examined by X-ray single crystal diffraction analysis.
X-ray crystallographic data
Data for 1k
Single crystals of 1k were obtained via the diffusion of
methanol into an Et2O solution at –4 °C. Formula C40H30Fe2,
fw ϭ 622.34; monoclinic crystal system, space group P21/c
(No. 14); a ϭ 18.075(3) Å, b ϭ 7.4082(11) Å, c ϭ
11.7293(16) Å; ␤ ϭ 103.751(3)°; V ϭ 1525.6(4) Å3; Z ϭ 2;
␳
ϭ 1.355 g cm–3; 2␪
ϭ 52.80°; ␮ ϭ 0.978 mm–1;
max
(calcd.)
Published by NRC Research Press

Zhao et al.
1007
T ϭ –80 °C; total data collected ϭ 7305. Final R1(F) ϭ 0.0562
raphy (TLC): aluminium sheet coated with silica gel F254 from
Whatman; visualization by UV light or KMnO4 stain. Melting
point: Fisher-Johns or Gallenkamp apparatus; uncorrected.
UV–vis spectra: Varian Cary 400 at rt; ␭ in nm (ε in L mol–1 cm–1).
IR spectra (cm–1): Nicolet Magna-IR 750 (neat) or Nic-Plan IR
(1455 observed reflections with Fo Ն 2␴(Fo )); wR2(F2) ϭ
0.0901 for 212 variables, 3133 unique reflections, and 0 re-
straints; residual electron density ϭ 0.326 and –0.327 e Å–3.
CCDC 862755.
2
2
1
microscope (solids). H and 13C solution-state NMR: Varian
Data for 1l
300, 400, 500, or 600 and Bruker AM-300 instruments, at rt in
CDCl3; solvent peaks (7.24 ppm for 1H and 77.0 ppm for 13C)
as reference. For simplicity, the coupling constants of the aryl
protons have been reported as pseudo-first-order, even though
they are AA=BB= second-order spin systems; coupling con-
stants are reported as observed. 13C solid-state NMR: CMX
Infinity 200 as well as Bruker Avance 300 and 500 spectrom-
eters operating at 50, 75, and 125 MHz, respectively, for 13C.
Samples were packed in 4 mm outside diameter (o.d.) MAS
rotors spinning at frequencies ranging from 5 to 12 kHz. All
spectra were acquired with cross polarization using contact
times of 1.0–6.0 ms, 1H 90° pulses of 2.5–4.0 ␮s, and recycle
delays of 3.0–10.0 s. To improve decoupling efficiency, the
two-pulse phase modulated (TPPM) sequence of Griffin and
co-workers46 was used. Spectra were referenced to tetrameth-
ylsilane (TMS; ␦ ϭ 0) by setting the high-frequency peak of
adamantine to 38.56 ppm.47 EI-MS (m/z): Kratos MS 50
instrument. ESI-MS (m/z): Micromass Zabspec oaTOF or PE
Biosystems Mariner TOF instruments. Elemental analyses
were performed by the Microanalytical Service, Department of
Chemistry, University of Alberta.
Single crystals of 1l were obtained via the diffusion of MeOH
into a CH2Cl2 solution at –20 °C (as reported in ref. 27). Formula
C38H54Si2, fw ϭ 566.99; monoclinic crystal system, space group
P21/c (No. 14); a ϭ 13.5571(8) Å, b ϭ 7.7132(5) Å, c ϭ
35.616(2) Å; ␤ ϭ 96.5990(10)°; V ϭ 3699.7(4) Å3; Z ϭ 4;
␳
ϭ 1.018 g cm–3; 2␪
ϭ 51.50°; ␮ ϭ 0.118 mmϪ1
;
(calcd.)
T ϭ –80 °C; total data collecmteadx ϭ 19122. Final R1(F) ϭ 0.0472
(4842 observed reflections with Fo Ն 2␴(Fo )); wR2(F2) ϭ
0.1366 for 365 variables, 7039 unique reflections, and 0 re-
straints; residual electron density ϭ 0.389 and –0.235 e Å–3.
CCDC HOZSAQ.
2
2
Data for 6a
Single crystals of 6a were obtained via the diffusion of
hexanes into a solution of hexanes/CH2Cl2 at –4 °C. For-
mula C24H10Br4, fw ϭ 617.96; triclinic crystal system,
space group P1 (No. 2); a ϭ 9.4512(7) Å, b ϭ 10.1187(7)
Å, c ϭ 11.6133(8) Å; ␣ ϭ 96.0941(13)°, ␤ ϭ 92.5663(13)°,
␥ ϭ 103.4569(13)°; V ϭ 1071.25(13) Å3; Z ϭ 2; ␳
ϭ
(calcd.)
1.916 g cm–3; 2␪max ϭ 52.76°; ␮ ϭ 7.521 mm–1; T ϭ –80 °C;
total data collected ϭ 7878. R1 ϭ 0.0368 (3413 observed
2
2
reflections with Fo Ն 2␴(Fo )); wR2 ϭ 0.0930 for 253
variables, 4356 unique reflections, and 0 restraints; residual
electron density ϭ 1.164 and –0.586 e Å–3. CCDC 862756.
General methods
Reagents and solvents were purchased reagent grade and
used without further purification. Compounds 2,29 3b,48 3g,49
3k,50 10a–10c,31 and 1135 were prepared based on literature
precedent. Anhydrous MgSO4 was used as the drying agent
after aqueous workup. Evaporation and concentration in vacuo
was done at H2O-aspirator pressure. All reactions were per-
formed in standard glassware under an inert atmosphere of Ar
or N2. A positive pressure of Ar or N2 was essential to the
success of all Pd-catalyzed reactions. Deoxygenation of sol-
vents was accomplished by vigorously bubbling Ar or N2
through the solution at rt for ~30 min. Brine refers to a
saturated aqueous solution of NaCl. Flash chromatography
was conducted on silica gel using the eluent system defined in
the individual experimental procedures.
Data for 6c
Single crystals of 6c were obtained via the diffusion of
hexanes into a solution of hexanes/CH2Cl2 at –4 °C. For-
mula C32H26Br4, fw ϭ 730.17; triclinic crystal system,
space group P1 (No. 2); a ϭ 5.8968(7) Å, b ϭ 11.1037(14)
Å,
c ϭ 11.9247(15) Å; ␣ ϭ 69.2510(17)°, ␤ ϭ
78.1507(18)°, ␥ ϭ 86.0880(19)°; V ϭ 714.58(15) Å3;
Z ϭ 1; ␳
ϭ 1.697 g cm–3; 2␪
ϭ 52.74°; ␮ ϭ
max
(calcd.)
5.651 mm–1; T ϭ –80 °C; total data collected ϭ 5606. R12ϭ
2
0.0342 (2418 observed reflections with Fo Ն 2␴(Fo ));
wR2 ϭ 0.0905 for 163 variables, 2911 unique reflections, and 0
restraints; residual electron density ϭ 0.618 and –0.492 e Å–3.
CCDC 862758.
For mass spectrometric analyses, low-resolution data are
provided in cases when Mϩ is not the base peak; otherwise,
only high-resolution data are provided. The samples for ESI
mass spectrometry were typically dissolved in ClCH2CH2Cl
and made use of a 3:1 MeOH/toluene mixture as the carrier
solvent.
DSC measurements were measured on a PerkinElmer Pyris
1 DSC instrument. Melting points from DSC analysis are
reported as the peak maxima, and in cases when the sample
decomposed, the onset temperature of the decomposition exo-
thermic peak is reported, as well as the exothermic maxima
corresponding to the decomposition.
Formation of the Hay catalyst was conducted as follows:
CuI (50 mg) and tetramethylethylenediamine (TMEDA,
75 mg) were added to CH2Cl2 (2 mL) and stirred until homo-
geneous; this solution was prepared fresh for each reaction.
Wet THF/MeOH refers to the use of THF and MeOH that have
not been previously dried by distillation, i.e., the solvent is
Data for 6d
Single crystals of 6c were obtained via the evaporation of a
CDCl3 solution at –4 °C. Formula C24H8Br4N2O4, fw ϭ
707.96; orthorhombic crystal system, space group Pbcn
(No. 60); a ϭ 7.5156(7) Å, b ϭ 14.8934(14) Å, c ϭ 21.328(2)
Å; V ϭ 2387.3(4) Å3; Z ϭ 4; ␳
2␪
ϭ 1.970 g cm–3;
ϭ 52.82°; ␮ ϭ 6.777 mm–1;(cTalcϭd.) –80 °C; total data
collected ϭ 14313. R1 ϭ 0.0322 (1968 observed reflections
max
2
2
with Fo Ն 2␴(Fo )); wR2 ϭ 0.0825 for 154 variables, 2461
unique reflections, and 0 restraints; residual electron density ϭ
1.129 and –0.406 e Å–3. CCDC 862757.
Synthetic and spectroscopic details
General experimental details
Column chromatography: silica gel 60 (230–400 mesh)
from General Intermediates of Canada. Thin-layer chromatog-
Published by NRC Research Press

1008
Can. J. Chem. Vol. 90, 2012
used “straight out of the bottle” and is assumed to contain a
small amount of water.
Compound 1b
Compound 4b (20 mg, 0.035 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 0.5 h as described in general
procedure C. Flash chromatography (hexane / ethyl acetate,
1:5) afforded 1b (16 mg, 91%) as a brown solid; mp 57–62 °C.
Rf ϭ 0.62 (hexane / ethyl acetate, 1:5). IR (CH2Cl2, cast, cm–1):
General procedure A — Desilylation procedure
To the appropriate trimethylsilyl polyyne in wet THF/
MeOH (1:1, 20 mL) was added K2CO3 (~20 mg), and the
resulting mixture was stirred at rt until TLC indicated the
starting material had been consumed (~2 h). Ether (50 mL) and
saturated aq NH4Cl (50 mL) were added, the organic phase
separated, washed with saturated aq NH4Cl (2 ϫ 50 mL),
dried over MgSO4, and filtered. The solvent was then reduced
to ~1 mL via rotary evaporation, taking care to ensure that the
product remained in solution during the concentration process.
The resulting solution was carried on to the next step.
1
2934, 2193, 1750, 1587, 1433. H NMR (600 MHz, CDCl3)
␦: 5.51 (d, J ϭ 3.5 Hz, 2H), 5.28 (t, J ϭ 10.1 Hz, 2H), 5.09
(dd, J ϭ 10.1 Hz, J ϭ 3.5 Hz, 2H), 5.02 (s, 2H), 4.29 (dd,
J ϭ 12.3 Hz, J ϭ 5.7 Hz, 2H), 4.13 (dd, J ϭ 12.3 Hz, J ϭ
2.4 Hz, 2H), 3.73 (d, J ϭ 17.0 Hz, 4H), 3.71 (m, 2H), 3.43 (d,
J ϭ 17.0 Hz, 4H), 2.16 (s, 6H), 2.07 (s, 12 H), 2.04 (s, 12H),
1.97 (s, 6H). 13C NMR (75 MHz, CDCl3, APT) ␦: 170.7,
170.1, 170.0, 169.7, 162.3, 99.7, 87.6, 80.9, 76.9, 76.4, 75.1,
72.1, 70.2, 69.6, 68.1, 65.8, 62.6, 31.8, 29.3, 23.4, 23.2, 20.80,
20.75, 20.66, 20.6. ESI-MS m/z (MeOH): 1029.3 ([M ϩ
Na]ϩ).
General procedure B — Palladium-catalyzed
cross-coupling procedure
The appropriate alkyne 3 was added to a solution of vinyl
triflate 2 in THF (20 mL) and the resulting mixture
deoxygenated. PdCl2(PPh3)2 (~0.05 equiv) and i-Pr2NH were
sequentially added, the solution was stirred for 5 min, CuI
(~0.15 equiv) was added, and the solution was stirred under
conditions described in the individual procedures, typically
until TLC analysis no longer showed the presence of either 2
or 3. Ether (40 mL) and H2O (30 mL) were then added, the
organic phase separated, washed with saturated aq NH4Cl
(2 ϫ 50 mL), dried over MgSO4, filtered, and the filtrate
concentrated in vacuo. Flash column chromatography and (or)
precipitation from MeOH gave the desired enyne oligomer.
Compound 1c
Compound 4c (68 mg, 0.24 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 0.5 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1) af-
forded 1c (32 mg, 66%) as a yellow waxy solid. Rf ϭ 0.61
(hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
(ε): 282
max
(91 200), 296 (82 100), 322 (41 900), 349 (18 600), 374
(19 900), 405 (11 800). IR (␮scope, cm–1): 3057, 2930, 2906,
1
General procedure C — Copper-catalyzed oxidative
acetylenic-coupling procedure
2194, 2127, 1598, 1583, 1490, 1443. H NMR (300 MHz,
CDCl3) ␦: 7.46–7.42 (m, 4H), 7.32–7.28 (m, 6H), 2.13 (s, 6H),
2.12 (s, 6H). 13C NMR (75 MHz, CDCl3, APT) ␦: 161.5,
131.5, 128.5, 128.4, 122.9, 100.4, 92.9, 84.4, 76.4, 75.0, 67.9,
64.1, 23.4, 23.3. EI HR-MS calcd for C32H22 (Mϩ): 406.1722;
found: 406.1728.
The terminal acetylene from general procedure A was added
to acetone (10 mL), acetone/CH2Cl2 (1:1, 10 mL), or CH2Cl2
(60 mL). A solution of Hay catalyst mixture (1 mL) was then
added. The mixture was stirred at rt under air until TLC
analysis no longer showed the deprotected polyyne (generally
less than 0.5 h). The reaction solution was concentrated in
vacuo to ~5 mL and diethyl ether (50 mL) was added. The
ethereal solution was consecutively washed with a 10% HCl
solution (25 mL), saturated aq NaHCO3 (25 mL), and brine
(25 mL), dried, and the solvent removed. Flash column chro-
matography and (or) precipitation from MeOH gave the prod-
uct 1 or 6.
Compound 1d
Compound 4d (88 mg, 0.27 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 0.5 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1) af-
forded 1d (64 mg, 95%) as a yellow solid; mp Ͼ 115 °C (dec).
Rf ϭ 0.57 (hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
(ε):
287 (66 700), 306 (90 400), 323 (83 700), 349 (50 20m0a)x, 374
(39 800), 405 (15 900). IR (␮scope, cm–1): 3104, 2932, 2847,
2198, 2128, 1594, 1520, 1491, 1432, 1343. 1H NMR
(400 MHz, CDCl3) ␦: 8.17 (d, J ϭ 8.8 Hz, 4H), 7.57 (d, J ϭ
8.8 Hz, 4H), 2.149 (s, 6H), 2.146 (s, 6H). 13C NMR (100 MHz,
CDCl3, APT) ␦: 163.9, 147.1, 132.1, 129.7, 123.6, 99.9, 90.8,
89.5, 76.7, 74.2, 68.1, 63.9, 23.54, 23.47. EI HR-MS calcd for
C32H20N2O4 (Mϩ): 496.1423; found: 496.1425. DSC: decom-
position 172 °C (onset), 193 °C (peak).
Compound 1a
Compound 4a (66 mg, 0.26 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 1 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1)
afforded 1a (45 mg, 94%) as a brown oil that slowly decom-
posed over a period of hours to days when stored neat. Rf ϭ
0.78 (hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
(ε): 302
max
(57 800), 320 (41 700), 348 (17 100), 374 (18 800), 405
(11 800). IR (CHCl3, cast, cm–1): 2958, 2932, 2872, 2193,
2125, 1959, 1587. 1H NMR (300 MHz, CDCl3) ␦: 2.33 (t, J ϭ
6.6 Hz, 4H), 2.02 (s, 6H), 2.01 (s, 6H), 1.54–1.36 (m, 8H),
0.90 (t, J ϭ 7.2 Hz, 6H). 13C NMR (75 MHz, CDCl3, APT) ␦:
159.7, 100.5, 94.2, 75.7, 75.8, 75.5, 67.7, 64.0, 30.8, 23.1,
23.0, 22.0, 19.2, 13.6. EI HR-MS calcd for C28H30 (Mϩ):
366.2347; found: 366.2349.
Compound 1e
Compound 4e (53 mg, 0.16 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 2 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1) af-
forded 1e (11 mg, 27%) as a yellow waxy semisolid that
Published by NRC Research Press

Zhao et al.
1009
slowly decomposed over a period of hours to days. Rf ϭ 0.28
121.8, 100.2, 91.7, 85.4, 76.4, 74.7, 67.9, 64.0, 23.4, 23.3. ESI
HR-MS (MeOH/toluene, 1:1) calcd for C32H2079Br2 (Mϩ):
561.9926; found: 561.9928. DSC: decomposition 123 °C (on-
set), 131 °C (peak).
(hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
(ε): 283
max
(72 300), 304 (63 000), 323 (52 600), 349 (28 500), 374
(27 000), 405 (14 700). IR (␮scope, cm–1): 2927, 2200, 1608,
1567, 1528, 1479, 1438, 1336. 1H NMR (400 MHz, CDCl3) ␦:
8.06 (dd, J ϭ 8.0, 1.2 Hz, 2H), 7.66 (dd, J ϭ 8.0, 1.6 Hz, 2H),
7.57 (td, J ϭ 8.0, 1.2 Hz, 2H), 7.44 (td, J ϭ 8.0, 1.6 Hz, 2H),
2.22 (s, 6H), 2.15 (s, 6H). 13C NMR (100 MHz, CDCl3, APT)
␦: 165.0, 149.0, 134.7, 132.9, 128.7, 124.7, 118.5, 100.1, 92.2,
88.0, 76.6, 74.3, 68.0, 64.0, 23.6, 23.5. EI HR-MS calcd for
C32H20N2O4 (Mϩ): 496.1423; found: 496.1419.
Compound 1j
Compound 4j (73 mg, 0.23 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone/CH2Cl2 (1:1; 10 mL) in the
presence of Hay catalyst (1 mL) and air for 20 min as de-
scribed in general procedure C. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 1j (43 mg, 76%) as a yellow solid;
mp Ͼ 115 °C (dec). Rf ϭ 0.52 (hexane/CH2Cl2, 2:1). UV–vis
Compound 1f
(CHCl3) ␭
(ε): 296 (94 600), 314 (92 000), 347 (46 900),
Compound 4f (77 mg, 0.24 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 0.5 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1) af-
forded 1f (23 mg, 39%) as a yellow waxy semisolid that
slowly decomposed over a period of hours to days. Rf ϭ 0.4
max
376 (24 000), 408 (12 800). IR (CHCl3, cast, cm–1): 2902,
2194, 2122, 1958, 1608, 1520, 1480, 1444. 1H NMR
(400 MHz, CDCl3) ␦: 7.31 (d, J ϭ 9.2 Hz, 4H), 6.61 (d, J ϭ
9.2 Hz, 4H), 2.96 (s, 12H), 2.10 (s, 6H), 2.09 (s, 6H). 13C
NMR (100 MHz, CDCl3, APT) ␦: 159.5, 150.2, 132.6, 111.7,
109.6, 100.7, 94.1, 82.3, 75.9, 75.5, 67.8, 64.1, 40.1, 23.2,
23.1. ESI HR-MS (MeOH/toluene, 1:1) calcd for C36H32N2
(Mϩ): 492.2565; found: 492.2560. DSC: decomposition
157 °C (onset), 165 °C (peak).
(hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
(ε): 280
max
(98 100), 299 (87 500), 320 (54 200), 348 (20 100), 374
(21 400), 405 (13 300). IR (CH2Cl2, cast, cm–1): 3087, 2197,
1
1536, 1346. H NMR (300 MHz, CDCl3) ␦: 8.28–8.27 (m,
Compound 1k
2H), 8.17–8.13 (m, 2H), 7.75–7.72 (m, 2H), 7.49 (t, J ϭ
8.1 Hz, 2H), 2.152 (s, 6H), 2.146 (s, 6H). 13C NMR (75 MHz,
CDCl3, APT) ␦: 163.4, 148.2, 137.1, 129.4, 126.3, 124.8,
123.1, 99.9, 90.2, 86.9, 74.3, 68.1, 64.0, 23.6, 23.5 (one
coincident peak not observed). EI HR-MS calcd for
C32H20N2O4 (Mϩ): 496.1423; found: 496.1409.
Compound 4k (70 mg, 0.18 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone/CH2Cl2 (1:1; 10 mL) in the
presence of Hay catalyst (1 mL) and air for 0.5 h as described
in general procedure C. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 1k (42 mg, 75%) as an orange solid;
mp Ͼ 120 °C (dec). Rf ϭ 0.4 (hexane/CH2Cl2, 2:1). UV–vis
Compound 1h
(CHCl3) ␭
(ε): 298 (78 800), 349 (19 400), 376 (18 400),
max
Compound 4h (40 mg, 0.13 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone (10 mL) in the presence of
Hay catalyst (1 mL) and air for 0.5 h as described in general
procedure C. Flash chromatography (hexane/CH2Cl2, 2:1) af-
forded 1h (22 mg, 74%) as a yellow waxy semisolid that
slowly decomposed over a period of hours to days when stored
407 (11 500). IR (␮scope, cm–1): 3098, 2987, 2932, 2904,
2214, 2191, 1577, 1424. 1H NMR (500 MHz, CDCl3) ␦: 4.42
(m, 4H), 4.20 (m, 14H), 2.08 (s, 6H), 2.07 (s, 6H). 13C NMR
(125 MHz, CDCl3, APT) ␦: 159.9, 100.7, 91.9, 80.5, 76.0,
75.3, 71.4, 69.9, 68.9, 67.8, 64.8, 64.1, 23.4, 23.2. ESI HR-MS
(MeOH/toluene, 3:1) calcd for C40H30Fe2 (Mϩ): 622.1046;
found: 622.1043. DSC: decomposition 160 °C (onset), 187 °C
(peak).
neat. Rf ϭ 0.63 (hexane/CH2Cl2, 2:1). UV–vis (CHCl3) ␭
max
(ε): 300 (104 400), 323 (69 600), 348 (17 600), 374 (17 700),
405 (9 700). IR (CH2Cl2, cast, cm–1): 2228, 2194, 2126, 1959,
Compound 4a
1
1603, 1450, 1432. H NMR (300 MHz, CDCl3) ␦: 7.59 (d,
Triflate 2 (108 mg, 0.333 mmol) was cross-coupled with
1-hexayne (30 mg, 0.36 mmol) in degassed THF (20 mL) in
the presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diisopro-
pylamine (2 mL), and CuI (6 mg, 0.03 mmol) for 3 h as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 4a (84 mg, 98%) as a colourless oil
that slowly turned brown. Rf ϭ 0.75 (hexane/CH2Cl2, 2:1). IR
(CH2Cl2, cast, cm–1): 2959, 2933, 2873, 2198, 2097. 1H NMR
(300 MHz, CDCl3) ␦: 2.32 (t, J ϭ 7.2 Hz, 2H), 2.00 (s, 3H),
1.98 (s, 3H), 1.56–1.36 (m, 4H), 0.90 (t, J ϭ 6.9 Hz, 3H), 0.18
(s, 9H). 13C NMR (125 MHz, CDCl3, APT) ␦: 157.0, 100.5,
93.3, 90.5, 88.1, 76.1, 75.4, 74.6, 30.8, 22.8, 22.7, 22.0, 19.1,
13.6, –0.4. EI-MS m/z (rel. intensity): 256 (Mϩ, 100), 241
([M – Me]ϩ, 88). EI HR-MS calcd for C17H24Si (Mϩ):
256.1647; found: 256.1642.
J ϭ 8.4 Hz, 4H), 7.51 (d, J ϭ 8.4 Hz, 4H), 2.14 (s, 12H). 13C
NMR (75 MHz, CDCl3, APT) ␦: 163.6, 132.1, 132.0, 127.8,
118.5, 111.8, 100.0, 91.1, 88.7, 76.7, 74.3, 68.1, 64.0, 23.6,
23.5. EI HR-MS calcd for C34H20N2 (Mϩ): 456.1627; found:
456.1629.
Compound 1i
Compound 4i (93 mg, 0.26 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and homocoupled in acetone/CH2Cl2 (1:1; 10 mL) in the
presence of Hay catalyst (1 mL) and air for 0.5 h as described
in general procedure C. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 1i (63 mg, 85%) as a yellow solid;
mp Ͼ 110 °C (dec). Rf ϭ 0.21 (hexane/CH2Cl2, 2:1). UV–vis
(CHCl3) ␭max (ε): 288 (104 300), 322 (49 000), 349 (17 600),
375 (20 100), 406 (12 200). IR (CH2Cl2, cast, cm–1): 2198,
Compound 4b
1
1589, 1485, 1425. H NMR (400 MHz, CDCl3) ␦: 7.43 (d,
Triflate 2 (32 mg, 0.099 mmol) was cross-coupled
with 2-propynl 2,3,4,6-O-acetyl-1-thio-␤-D-mannopyranoside
(40 mg, 0.099 mmol) in degassed THF (20 mL) in the pres-
J ϭ 8.8 Hz, 4H), 7.29 (d, J ϭ 8.8 Hz, 4H), 2.11 (s, 12H). 13C
NMR (100 MHz, CDCl3, APT) ␦: 162.0, 132.8, 131.6, 122.7,
Published by NRC Research Press

1010
Can. J. Chem. Vol. 90, 2012
ence of PdCl2(PPh3)2 (3 mg, 0.004 mmol), diisopropylamine
(2 mL), and CuI (1.5 mg, 0.0079 mmol) for 1 h as described
in general procedure B. Flash chromatography (hexane / ethyl
acetate, 3:1) afforded 4b (37 mg, 65%) as a colourless solid
vide infra; mp 54–57 °C. Rf ϭ 0.33 (hexane / ethyl acetate,
3:1). IR (␮scope, cm–1): 2961, 2916, 2849, 2199, 2098, 1744,
in the presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diiso-
propylamine (2 mL), and CuI (6 mg, 0.032 mmol) for 2 h as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 1:1) afforded 4e (95 mg, 87%) as a yellow solid;
mp 93–94 °C. Rf ϭ 0.45 (hexane/CH2Cl2, 1:1). IR (CH2Cl2,
cast, cm–1): 2960, 2199, 2094, 1607, 1526, 1480, 1438, 1343.
1H NMR (400 MHz, CDCl3) ␦: 8.02 (dd, J ϭ 8.3, 1.2 Hz, 1H),
7.62 (dd, J ϭ 7.8, 1.5 Hz, 1H), 7.54 (dt, J ϭ 7.5, 1.3 Hz, 1H),
7.41 (dt, J ϭ 8.3, 1.5 Hz, 1H), 2.17 (s, 3H), 2.11 (s, 3H), 0.19
(s, 9H). 13C NMR (100 MHz, CDCl3, APT) ␦: 162.4, 148.9,
134.6, 132.8, 128.5, 124.6, 118.6, 100.2, 93.0, 91.2, 87.9, 87.3,
76.3, 73.1, 23.3, 23.2, –0.4. EI MS m/z (rel. intensity): 321.1
(Mϩ, 35), 73.0 (Me3Siϩ, 100). EI HR-MS calcd for
C19H19NO2Si (Mϩ): 321.1185; found: 321.1182. Anal. calcd
for C19H19NO2Si: C 70.99, H 5.96, N 4.36; found: C 71.10, H
5.95, N 4.29.
1
1592, 1433. H NMR (600 MHz, CDCl3) ␦: 5.51 (d, J ϭ
3.5 Hz, 1H), 5.28 (t, J ϭ 10.0 Hz, 1H), 5.09 (dd, J ϭ 10.0 Hz,
J ϭ 3.6 Hz, 1H), 5.02 (s, 1H), 4.29 (dd, J ϭ 10.0 Hz, J ϭ
0.6 Hz, 1H), 4.13 (dd, J ϭ 10.0 Hz, J ϭ 0.2 Hz, 1H), 3.72 (d,
J ϭ 16.7 Hz, 1H), 3.70 (m, 1H), 3.42 (d, J ϭ 16.7 Hz, 1H),
2.16 (s, 3H), 2.07 (s, 3H), 2.05 (s, 3H), 2.023 (s, 3H), 2.020 (s,
3H), 1.96 (s, 3H), 0.18 (s, 9H). 13C NMR (75 MHz, CD2Cl2,
APT) ␦: 170.8, 170.4, 170.2, 169.9, 160.4, 99.9, 91.6, 87.8,
87.5, 81.3, 79.8, 77.1, 76.3, 74.0, 72.3, 70.5, 66.0, 62.7, 30.1,
23.2, 23.0, 20.9, 20.7, 19.6, –0.4 (one coincident peak not
observed). ESI HR-MS calcd for C28H36O9NaSSi ([M ϩ
Na]ϩ): 599.1742; found: 599.1740.
Compound 4f
Trimethyl(3-nitrophenylethynyl)silane (75 mg, 0.34 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described
in general procedure A to give 3f, which was cross-coupled
with triflate 2 (109 mg, 0.336 mol) in degassed THF (20 mL)
in the presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diiso-
propylamine (2 mL), and CuI (6 mg, 0.032 mmol) for 10 min
as described in general procedure B. Flash chromatography
(hexane/CH2Cl2, 1:1) afforded 4f (98 mg, 91%) as a yellow
solid; mp 77–78 °C. Rf ϭ 0.49 (hexane/CH2Cl2, 1:1). IR
(CH2Cl2, cast, cm–1): 3084, 2960, 2904, 2200, 2095, 1572,
1532, 1477, 1433, 1351. 1H NMR (400 MHz, CDCl3) ␦:
8.27–8.25 (m, 1H), 8.15–8.11 (m, 1H), 7.72 (dt, J ϭ 7.5,
1.1 Hz, 1H), 7.48 (t, J ϭ 7.9 Hz, 1H), 2.12 (s, 3H), 2.11 (s,
3H), 0.19 (s, 9H). 13C NMR (75 MHz, CDCl3, APT) ␦: 160.7,
148.2, 137.1, 129.4, 126.2, 125.0, 122.9, 100.1, 91.5, 89.6,
87.8, 87.7, 73.1, 23.3, 23.2, Ϫ0.4 (one signal coincident or not
observed). EI MS m/z (rel. intensity): 321.1 (Mϩ, 100), 306.1
([M – Me]ϩ, 48). EI HR-MS calcd for C19H19NO2Si (Mϩ):
321.1185; found: 321.1176.
Compound 4c
Trimethylphenylethynylsilane (60 mg, 0.34 mmol) was desi-
lylated with K2CO3 in THF/MeOH (1:1) as per general pro-
cedure A to give 3c, which was cross-coupled with triflate 2
(109 mg, 0.336 mmol) in degassed THF (20 mL) in the
presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diisopro-
pylamine (2 mL), and CuI (6 mg, 0.03 mmol) for 50 min as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 4c (90 mg, 96%) as a colourless
solid; mp 71–72 °C. Rf ϭ 0.63 (hexane/CH2Cl2, 2:1). IR
(CH2Cl2, cast, cm–1): 2960, 2904, 2199, 2094, 1594, 1489. 1H
NMR (400 MHz, CDCl3) ␦: 7.45–7.42 (m, 2H), 7.31–7.27 (m,
3H), 2.10 (s, 3H), 2.09 (s, 3H), 0.20 (s, 9H). 13C NMR
(100 MHz, CDCl3, APT) ␦: 158.8, 131.4, 128.25, 128.19,
123.1, 100.5, 92.1, 90.9, 88.0, 85.0, 76.0, 73.8, 23.00, 23.06, –0.4.
EI MS m/z (rel. intensity): 276.1 (Mϩ, 100), 261.1 ([M Ϫ Me]ϩ, 88).
EI HR-MS calcd for C19H20Si (Mϩ): 276.1334; found: 276.1334.
Compound 4d
Trimethyl(4-nitrophenylethynyl)silane (75 mg, 0.34 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described
in general procedure A to give 3d, which was cross-coupled
with triflate 2 (109 mg, 0.336 mmol) in degassed THF (20 mL)
in the presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diiso-
propylamine (2 mL), and CuI (6 mg, 0.03 mmol) for 50 min as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 1:1) afforded 4d (97 mg, 90%) as a yellow solid;
mp 94–95 °C. Rf ϭ 0.40 (hexane/CH2Cl2, 1:1). IR (CHCl3,
cast, cm–1): 2960, 2199, 2095, 1595, 1519, 1491, 1433, 1342.
1H NMR (400 MHz, CDCl3) ␦: 8.15 (d, J ϭ 8.9 Hz, 2H), 7.54
(d, J ϭ 8.9 Hz, 2H), 2.11 (s, 6H), 0.19 (s, 9H). 13C NMR
(100 MHz, CDCl3, APT) ␦: 161.2, 146.9, 132.0, 129.9, 123.5,
100.1, 91.5, 90.3, 90.2, 87.6, 76.6, 72.8, 23.22, 23.19, –0.5. EI
MS m/z (rel. intensity): 321.1 (Mϩ, 100), 306.1 ([M Ϫ Me]ϩ,
58). EI HR-MS calcd for C19H19NO2Si (Mϩ): 321.1185;
found: 321.1180. Anal. calcd for C19H19NO2Si: C 70.99, H
5.96; found: C 70.88, H 5.96.
Compound 4g
Trimethyl(5-nitrothienyl-2-ylethynyl)silane (76 mg, 0.34 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described in
general procedure A to give 3g, which was cross-coupled with
triflate 2 (109 mg, 0.336 mmol) in degassed THF (20 mL) in the
presence of PdCl2(PPh3)2 (12 mg, 0.017 mmol), diisopro-
pylamine (2 mL), and CuI (6 mg, 0.03 mmol) for 1 h as described
in general procedure B. Flash chromatography (hexane/CH2Cl2,
2:1) afforded 4g (40 mg, 36%) as a yellow solid; mp 68–69 °C.
Rf ϭ 0.18 (hexane/CH2Cl2, 1:1). IR (CH2Cl2, cast, cm–1): 3108,
1
2960, 2196, 2097, 1587, 1531, 1503, 1430, 1332. H NMR
(400 MHz, CDCl3) ␦: 7.77 (d, J ϭ 4.4 Hz, 1H), 7.06 (d, J ϭ
4.4 Hz, 1H), 2.11 (s, 3H), 2.09 (s, 3H), 0.20 (s, 9H). 13C NMR
(100 MHz, CDCl3, APT) ␦: 162.4, 150.8, 130.8, 130.6, 128.5,
99.8, 93.8, 91.9, 87.5, 83.6, 77.0, 72.1, 23.4, 23.3, –0.5. EI
HR-MS calcd for C17H17NO2SSi (Mϩ): 327.0749; found:
327.0749.
Compound 4h
4-Trimethylsilylethynylbenzonitrile (43 mg, 0.22 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described
in general procedure A to give 3h, which was cross-coupled
with triflate 2 (70 mg, 0.22 mmol) in degassed THF (20 mL)
in the presence of PdCl2(PPh3)2 (6 mg, 0.009 mmol), diiso-
Compound 4e
Trimethyl(2-nitrophenylethynyl)silane (75 mg, 0.34 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described
in general procedure A to give 3e, which was cross-coupled
with triflate 2 (109 mg, 0.336 mmol) in degassed THF (20 mL)
Published by NRC Research Press

Zhao et al.
1011
propylamine (2 mL), and CuI (3 mg, 0.02 mmol) for 1.5 h as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 1:1) afforded 4h (52 mg, 80%) as a yellow solid;
mp 60–62 °C. Rf ϭ 0.48 (hexane/CH2Cl2, 1:1). IR (CH2Cl2,
cast, cm–1): 2960, 2904, 2229, 2199, 2095, 1604, 1499, 1433.
1H NMR (400 MHz, CDCl3) ␦: 7.59 (d, J ϭ 8.6 Hz, 2H), 7.50
(d, J ϭ 8.6 Hz, 2H), 2.11 (s, 6H), 0.20 (s, 9H). 13C NMR
(75 MHz, CDCl3, APT) ␦: 160.9, 132.0, 131.9, 128.1, 118.5,
111.6, 100.2, 91.5, 90.4, 89.5, 87.7, 73.0, 23.3, –0.4 (two
coincident peaks not observed). EI MS m/z (rel. intensity):
301.1 (Mϩ, 93), 286.1 ([M – Me]ϩ, 100). EI HR-MS calcd for
C20H19NSi (Mϩ): 301.1287; found: 301.1292.
APT) ␦: 157.6, 100.9, 91.1, 90.7, 88.1, 81.2, 74.2, 71.4, 70.0,
68.8, 65.1, 23.1, 22.9, –0.3 (one coincident peak not ob-
served). EI HR-MS calcd for C23H24FeSi (Mϩ): 384.0997;
found: 384.1001.
Compound 6a
Compound 10a (62.5 mg, 0.164 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and the resulting product was subjected to a homocoupling
reaction in CH2Cl2 (60 mL) in the presence of Hay catalyst
(1 mL) and air as described in general procedure C. Flash
chromatography (hexanes/CH2Cl2, 7:1) gave 6a (38.0 mg,
75%) as a yellow crystalline solid; mp 185 °C (dec). Rf ϭ 0.46
(hexanes/CH2Cl2, 7:1). UV–vis (THF) ␭max (ε): 299 (66 600),
314 (78 600), 330 (64 700), 359 (27 600), 386 (30 600), 419
(19 500). IR (CHCl3, cast, cm–1): 3010, 2192, 1524, 1488. 1H
NMR (500 MHz, CDCl3) ␦: 7.36 (s). 13C NMR (100 MHz,
CDCl3) ␦: 136.6, 129.5, 129.1, 128.7, 128.5, 105.3, 81.9, 76.5,
70.9, 64.9. EI MS m/z (rel. intensity): 617.7 (Mϩ, 80), 298.1
([M – 4Br]ϩ, 100). HR-MS calcd for C24H1079Br281Br2 (Mϩ):
617.7475; found: 617.7488. Anal. calcd for C24H10Br4: C
46.66, H 1.63; found: C 46.35, H 1.46. DSC: decomposition
191 °C (onset), 192 °C (peak).
Compound 4i
(4-Bromophenylethynyl)trimethylsilane (101 mg, 0.399 mmol)
was desilylated with K2CO3 in THF/MeOH (1:1) as described
in general procedure A to give 3i, which was cross-coupled
with triflate 2 (130 mg, 0.401 mmol) in degassed THF (20 mL)
in the presence of PdCl2(PPh3)2 (14 mg, 0.020 mmol), diiso-
propylamine (2 mL), and CuI (7 mg, 0.04 mmol) for 2 h as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 1:1) afforded 4i (112 mg, 79%) as a colourless
waxy solid. Rf ϭ 0.80 (hexane/CH2Cl2, 1:1). IR (CHCl3,
cast, cm–1): 2959, 2198, 2094, 1484, 1421. 1H NMR
(400 MHz, CDCl3) ␦: 7.42 (d, J ϭ 8.4 Hz, 2H), 7.28 (d, J ϭ
8.4 Hz, 2H), 2.08 (s, 6H), 0.20 (s, 9H). 13C NMR (75 MHz,
CDCl3, APT) ␦: 159.3, 132.8, 131.5, 122.5, 122.0, 100.4, 91.1,
91.0, 87.9, 86.2, 76.2, 73.5, 23.1, 23.0, –0.4. EI HR-MS calcd
for C19H1981BrSi (Mϩ): 356.0419; found: 356.0419.
Compound 6b
Compound 10b (582 mg, 1.42 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and the resulting product was subjected to a homocoupling
reaction in CH2Cl2 (60 mL) in the presence of Hay catalyst
(1 mL) and air as described in general procedure C. Flash
chromatography (hexanes/CH2Cl2, 3:1) gave 6b (223 mg,
46%) as a yellow-green solid; mp 168–170 °C. Rf ϭ 0.41
Compound 4j
N,N-Dimethyl(4-trimethylsilylethynylphenyl)amine (109 mg,
0.501 mmol) was desilylated with K2CO3 in THF/MeOH (1:1)
as described in general procedure A to give 3j, which was
cross-coupled with triflate 2 (162 mg, 0.501 mmol) in de-
gassed THF (20 mL) in the presence of PdCl2(PPh3)2 (18 mg,
0.026 mmol), diisopropylamine (2 mL), and CuI (9 mg,
0.05 mmol) for 1.5 h as described in general procedure B.
Flash chromatography (hexane/CH2Cl2, 2:1) afforded 4j
(133 mg, 83%) as a yellow solid; mp 82–83 °C. Rf ϭ 0.50
(hexane/CH2Cl2, 2:1). IR (CHCl3, cast, cm–1): 2959, 2902,
(hexanes/CH2Cl2, 3:1). UV–vis (THF) ␭
(ε): 296 (80 200,
sh), 308 (93 100), 331 (59 200, sh), m3ax60 (26 900), 388
(27 800), 420 (18 300). IR (CHCl3, cast, cm–1): 2924, 2190,
1
1605, 1505, 1252. H NMR (300 MHz, CDCl3) ␦: 7.32 (d,
J ϭ 9.0 Hz, 4H), 6.88 (d, J ϭ 9.0 Hz, 4H), 3.81 (s, 6H). 13C
NMR (100 MHz, CDCl3, APT) ␦: 156.0, 123.0, 129.1, 128.8,
114.0, 104.2, 81.7, 70.9, 65.0, 55.3 (one signal coincident or
not observed). EI HR-MS calcd for C26H1479Br281Br2O2
(Mϩ): 677.7686; found: 677.7697. Anal. calcd for
C26H14Br4O2: C 46.06, H 2.08; found: C 45.87, H 1.93. DSC:
mp 176 °C; decomposition 176 °C (onset), 179 °C (peak).
1
2200, 2094, 1609, 1521, 1481, 1445. H NMR (400 MHz,
CDCl3) ␦: 7.30 (d, J ϭ 8.8 Hz, 2H), 6.60 (d, J ϭ 8.8 Hz, 2H),
2.96 (s, 6H), 2.09 (s, 3H), 2.07 (s, 3H), 0.22 (s, 9H). 13C NMR
(100 MHz, CDCl3, APT) ␦: 156.9, 150.0, 132.5, 111.7, 109.8,
100.9, 93.3, 90.5, 88.2, 82.9, 75.6, 74.4, 40.1, 22.9, 22.8, –0.4.
EI HR-MS calcd for C21H25NSi (Mϩ): 319.1756; found:
319.1750. Anal. calcd for C21H25NSi: C 78.94, H 7.89, N
4.38; found: C 78.70, H 8.04, N 4.47.
Compound 6c
Compound 10c (401 mg, 0.914 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and the resulting product was subjected to a homocoupling
reaction in CH2Cl2 (60 mL) in the presence of Hay catalyst
(1 mL) and air as described in general procedure C. Flash
chromatography (hexanes/CH2Cl2, 7:1) gave 6c (265 mg,
80%) as a yellow crystalline solid; mp 168–179 °C (dec). Rf ϭ
Compound 4k
Ethynylferrocene 3k (76 mg, 0.36 mmol) was cross-coupled
with triflate 2 (117 mg, 0.362 mmol) in degassed THF (20 mL)
in the presence of PdCl2(PPh3)2 (13 mg, 0.018 mmol), diiso-
propylamine (2 mL), and CuI (7 mg, 0.04 mmol) for 2 h as
described in general procedure B. Flash chromatography (hex-
ane/CH2Cl2, 2:1) afforded 4k (78 mg, 56%) as a yellow solid;
mp 84–85 °C. Rf ϭ 0.82 (hexane/CH2Cl2, 2:1). IR
(␮scope, cm–1): 3099, 2964, 2908, 2214, 2191, 2091, 1593,
0.52 (hexanes/CH2Cl2, 7:1). UV–vis (THF) ␭
(ε): 299
max
(72 100), 309 (70 500), 331 (55 100), 359 (25 200), 387
(27 600), 419 (17 500). IR (CHCl3, cast, cm–1): 2963, 2182,
1
1531. H NMR (300 MHz, CDCl3) ␦: 7.38 (d, J ϭ 8.7 Hz,
4H), 8.7 (d, J ϭ 8.7 Hz, 4H), 1.30 (s, 18H). 13C NMR
(100 MHz, CDCl3) ␦: 152.3, 133.5, 129.4, 128.2, 125.6, 104.6,
81.8, 77.3, 70.9, 65.0, 34.9, 31.3. EI HR-MS calcd for
C32H2679Br281Br2 (Mϩ): 729.8727; found: 729.8750. DSC:
decomposition initial onset ~200 °C; 229 °C (onset), 233 °C
(peak).
1
1426, 1410. H NMR (600 MHz, CDCl3) ␦: 4.42 (t, J ϭ
1.8 Hz, 2H), 4.21 (s, 5H), 4.19 (t, J ϭ 1.8 Hz, 2H), 2.06 (s,
3H), 2.05 (s, 3H), 0.19 (s, 9H). 13C NMR (75 MHz, CDCl3,
Published by NRC Research Press

1012
Can. J. Chem. Vol. 90, 2012
Compound 6d
Compound 11
13CBr4 (287 mg, 0.865 mmol), CBr4 (431 mg, 1.30 mmol),
and PPh3 (1.14 g, 4.33 mmol) were added to CH2Cl2 (15 mL)
at 0 °C and the solution stirred for ~5 min at rt until the mixture
turned bright orange. Triisopropylsilylpropargylaldehyde (501 mg,
2.38 mmol) dissolved in CH2Cl2 (~2 mL) was added in one
portion. The reaction was allowed to warm to rt and monitored by
TLC analysis until the ketone was no longer observed (~1 h).
When the reaction was judged complete, the solvent was reduced
to ~5 mL, hexanes (25 mL) were added, the inhomogeneous
mixture filtered through a plug of Celite layered on top of silica
gel, and the resulting filtrate concentrated in vacuo. This process
can be repeated a second time if necessary to remove phosphine/
phosphonium byproducts. Column chromatography gave 11
(638 mg, 73%) with ~34% labelling. Spectral data are consistent
with those previously reported, see ref. 35. 1H NMR (500 MHz,
CDCl3) ␦: 6.59 (d, J ϭ 1.5 Hz, 1H), 1.08 (s, 21H). 13C NMR
(125 MHz, CDCl3) ␦: 120.0 (d, 1J ϭ 360 Hz), 102.9 (C*, s and
d, 1J ϭ 360 Hz), 102.5 (s), 100.8 (d, 3J ϭ 25 Hz), 18.6, 11.1.
Compound 10d (1.10 g, 2.58 mmol) was desilylated with
K2CO3 in MeOH/THF (1:1) as described in general procedure
A, and the resulting product was subjected to a homocoupling
reaction in CH2Cl2 (60 mL) in the presence of Hay catalyst
(1 mL) and air as described in general procedure C. Flash
chromatography (hexanes/CH2Cl2, 1:1) gave 6d (469 mg,
51%) as a yellow crystalline solid; mp Ͼ 190 °C (dec). Rf ϭ
0.4 (hexanes/CH2Cl2, 1:1). UV–vis (THF) ␭
(ε): 296
max
(80 200), 312 (106 200), 331 (80 000), 359 (29 200), 387
(31 700), 419 (19 900). IR (CHCl3, cast, cm–1): 3104, 2188,
1
2114, 1517, 1346. H NMR (400 MHz, CDCl3) ␦: 8.24 (d,
J ϭ 9.2 Hz, 4H), 7.57 (d, J ϭ 9.2 Hz, 4H). 13C NMR (100 MHz,
CDCl3) ␦: 147.8, 142.5, 129.6, 127.4, 123.8, 107.5, 82.6, 75.4,
71.2, 64.8. EI MS m/z (rel. intensity): 707.7 (Mϩ, 23), 388.0
([M – 4Br]ϩ, 6). HR-MS calcd for C24H879Br281Br2N2O4:
707.7177 (Mϩ); found: 707.7217. Anal. calcd for
C24H8Br4N2O4: C 40.72, H 1.14, N 3.96; found: C 40.94, H
1.10, N 3.80. DSC: decomposition 189 °C (onset), 191 °C
(peak).
Compound 12
To a solution of compound 11 (638 mg, 1.74 mmol) in Et2O
(2 mL) at –78 °C was added via cannula a solution of LDA
(formed from BuLi (2.5 mol/L in hexanes, 2.1 mL, 5.3 mmol)
and diisopropylamine (0.73 mL, 0.53 mg, 5.23 mmol) in Et2O
(17 mL)) at –78 °C, and the resulting solution was stirred for
2 h at –78 °C. To this mixture was added dropwise Me3SiCl
(0.33 mL, 0.28 mg, 2.61 mmol). The reaction was allowed to
warm to rt and stirred overnight. Et2O (10 mL) and saturated
aq NH4Cl (10 mL) were added. The organic phase was sepa-
rated, washed with brine (2 ϫ 10 mL), and dried over MgSO4.
Solvent removal and purification by column chromatography
(silica gel, hexanes) afforded 12 (325 mg, 67%) as a colourless
oil. Rf ϭ 0.67 (hexanes), which was carried on to the next step
without further purification.
Compound 10d
Under an inert atmosphere of nitrogen, 4-nitrobenzoyl chlo-
ride (2.45 g, 13.2 mmol) and bis(trimethylsilyl)butadiyne (8;
2.30 g, 11.8 mmol) were dissolved in CH2Cl2 (100 mL) and
the temperature of the solution lowered to –20 °C. AlCl3
(2.4 g, 18.0 mmol) was added slowly over ~1 min, the cooling
bath removed, and the reaction mixture allowed to warm to rt
over ~3 h. The reaction was carefully quenched by the addition
of the reaction mixture to 10% HCl (50 mL) in ice (50 mL).
(Caution: This step is exothermic and can cause the CH2Cl2 to
boil!) Et2O (70 mL) was added, the organic layer separated,
washed with saturated aq NaHCO3 (2 ϫ 20 mL) and brine
(2 ϫ 20 mL), dried over MgSO4, and the solvent removed in
vacuo. The resulting product 9d was carried on to the next step
without further purification.
Compound 14
Under an inert atmosphere of nitrogen, 4-nitrobenzoyl chlo-
ride (239 mg, 1.29 mmol) and compound 12 (321 mg,
1.15 mmol) were dissolved in CH2Cl2 (12 mL) and the tem-
perature of the solution lowered to –20 °C. AlCl3 (230 mg,
1.72 mmol) was added slowly over ~1 min, the cooling bath
removed, and the reaction mixture allowed to warm to rt over
~3 h. The reaction was carefully quenched by the addition of
the reaction mixture to 10% HCl (25 mL) in ice (25 mL).
(Caution: This step is exothermic and can cause the CH2Cl2 to
boil!) Et2O (50 mL) was added, the organic layer separated,
washed with saturated aq NaHCO3 (2 ϫ 20 mL) and brine
(2 ϫ 20 mL), dried over MgSO4, and the solvent removed in
vacuo to give ketone 13 as a colourless oil. The ketone 13 was
carried on to the next step without further purification.
CBr4 (764 mg, 2.30 mmol) and PPh3 (1.21 g, 4.61 mmol)
were added to CH2Cl2 (12 mL) at 0 °C and the solution stirred
for ~5 min at rt until the mixture turned bright orange. Ketone
13, dissolved in CH2Cl2 (~2 mL), was added in one portion.
The reaction was allowed to warm to rt and monitored by TLC
analysis until the ketone was no longer observed (~1 h). When
the reaction was judged complete, the solvent was reduced to
~5 mL, hexanes (50 mL) were added, and the inhomogeneous
mixture filtered through a plug of Celite layered on top of
silica gel. The resulting filtrate was concentrated in vacuo to
give compound 14 (206 mg, 35%) as a colourless oil.
CBr4 (3.15 g, 9.50 mmol) and PPh3 (5.00 g, 19.1 mmol)
were added to CH2Cl2 (100 mL) at 0 °C and the solution
stirred for ~5 min at rt until the mixture turned orange. The
ketone 9d, dissolved in CH2Cl2 (~5 mL), was added in one
portion. The reaction was allowed to warm to rt and monitored
by TLC analysis until the ketone was no longer observed
(~1 h). When the reaction was judged complete, the solvent
was reduced to ~5 mL, hexanes (50 mL) were added, the
inhomogeneous mixture filtered through a plug of Celite lay-
ered on top of silica gel, and the resulting filtrate was concen-
trated in vacuo. This process can be repeated a second time if
necessary to remove phosphine/phosphonium byproducts.
Column chromatography (silica gel, hexanes/CH2Cl2, 1:1)
gave 10d (2.54 g, 51%) as a cream-coloured powder; mp
80–83 °C. Rf ϭ 0.60 (hexanes/CH2Cl2, 1:1). IR (CHCl3, cast
1
film, cm–1): 2960, 2096, 1595, 1523. H NMR (300 MHz,
CDCl3) ␦: 8.22 (d, J ϭ 8.7 Hz, 2H), 7.58 (d, J ϭ 8.7 Hz, 2H),
0.19 (s, 9H). 13C NMR (125 MHz, CDCl3, APT) ␦: 147.7,
143.4, 129.7, 128.1, 123.8, 104.8, 96.7, 86.8, 83.2, 73.8, –0.6.
EI MS m/z (rel. intensity): 426.9 (Mϩ, 28), 411.9 ([M –
CH3]ϩ, 100). HR-MS calcd for C15H13NO2Si79Br81Br (Mϩ):
426.9062; found: 426.9064. Anal. calcd for C15H13NO2SiBr2:
C 42.18, H 3.07, N 3.28; found: C 42.30, H 2.81, N 3.16.
Published by NRC Research Press

Zhao et al.
1013
13C NMR (125 MHz, CDCl3) ␦: 147.7, 143.5, 129.7, 128.3
(d, J ϭ 98 Hz), 123.8, 104.5, 94.3, 88.5 (d, J ϭ 18 Hz), 83.6
(d, J ϭ 202 Hz), 72.7 (C*, m), 18.5, 11.2.
(10) Baughman, R. H. J. Polym. Sci., Polym. Phys. Ed. 1974, 12 (8),
1511. doi:10.1002/pol.1974.180120801.
(11) Bloor, D.; Chance, R. R., Eds. Polydiacetylenes; Martinus
Nijhoff: Dordrecht, 1985.
Compounds 6d/6d*/6d**
(12) Wegner, G. Z. Naturforsch. 1969, 24b, 824.
To compound 14 (206 mg, 0.403 mmol) in THF (6 mL) was
added TBAF (1.0 mol/L in THF, 0.52 mL, 0.52 mmol). The
solution was stirred at rt until TLC analysis showed complete
conversion to the terminal alkyne. Et2O and saturated aq
NH4Cl were added, the organic phase was separated, washed
with saturated aq NH4Cl (2 ϫ 10 mL) and brine (10 mL), and
then dried over MgSO4. The solution was concentrated to
1–2 mL via rotary evaporation and diluted with CH2Cl2
(6 mL). Hay catalyst (1 mL) was added and the reaction
continued as described in general procedure C to give a
mixture of isotopomers 6d/6d*/6d** (59.7 mg, 42%). Spectral
data were consistent with those of 6d. 13C NMR (125 MHz,
CDCl3) ␦: 147.9, 142.7, 129.7, 127.6 (d, J ϭ 98 Hz), 124.0,
107.6, 82.7 (d, J ϭ 187 Hz), 75.6 (C*, m), 71.4 (d, J ϭ 32 Hz),
64.9.
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Supplementary data
(18) For theoretical predictions see Yang, S.; Kertesz, M. Macro-
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Chemistry 2009, 15 (36), 9105. doi:10.1002/chem.200900985;
(b) Mizukoshi, K.; Okada, S.; Kimura, T.; Shimada, S.; Mat-
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bcsj.81.1028; (c) Xiao, J.; Yang, M.; Lauher, J. W.; Fowler,
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Supplementary data are available with the article through
the journal Web site at http://nrcresearchpress.com/doi/suppl/
10.1139/v2012-075). CCDC HOZSAQ and 862755–862758
contain the X-ray data in CIF format for this manuscript.
These data can be obtained, free of charge, via http://www.
ccdc.cam.ac.uk/products/csd/request (or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: 44 1223 336033; or e-mail: deposit@ccdc.
cam.ac.uk).
Acknowledgments
We are grateful for financial support for this work as pro-
vided by the University of Alberta, the Alberta Ingenuity
Fund, the Natural Sciences and Engineering Research Council
of Canada (NSERC), and Petro Canada (Young Innovator
Award to R.R.T.). R.E.W. is a Canada Research Chair in
Physical Chemistry at the University of Alberta.
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