Alkyne migration in alkylidene carbenoid species: A new method of polyyne synthesis

Article abstract of DOI:10.1002/chem.200204584

The synthesis of conjugated polyyne structures via a modification of the Fritsch-Buttenberg-Wiechell (FBW) rearrangement is reported. Our adaptation provides for the 1,2-migration of an alkyne in a carbene/carbenoid intermediate that is conveniently effec

Full text of DOI:10.1002/chem.200204584

FULL PAPER
Alkyne Migration in Alkylidene Carbenoid Species:
A New Method of Polyyne Synthesis
Sara Eisler, Navjot Chahal, Robert McDonald, and Rik R. Tykwinski*[a]
Dedicated to Professor Ronald Caple on the occasion of his 65th birthday
Abstract: The synthesis of conjugated
polyyne structures via a modification
of the Fritsch Buttenberg Wiechell
(FBW) rearrangement is reported. Our
adaptation provides for the 1,2-migra-
tion of an alkyne in a carbene/carbenoid
intermediate that is conveniently effect-
ed via lithium halogen exchange with
the appropriate dibromo-olefinic pre-
cursor. This rearrangement is quite rap-
idly accomplished under mild conditions
(hexane solution, À788C),and the
seemingly high migratory aptitude of
the alkynyl moiety provides for efficient
rearrangement. This,in turn,allows for
multiple rearrangements in a single
molecule,greatly facilitating the con-
struction of highly unsaturated sub-
strates. This procedure is exploited for
the rapid synthesis of symmetrical and
unsymmetrical 1,3,5-hexatriynes, ex-
tended polyynes,and aryl polyyne build-
ing blocks. Most significantly,many of
these structures have been or would be
difficult to access via more traditional
transition metal catalyzed homo- or
cross-coupling techniques.
Keywords: alkynes
¥
carbenes
¥
¥
carbenoids
polyynes
¥
nanostructures
metal centers.[12] As well,the synthesis of cyclic molecular
carbon allotropes composed only of acetylenic carbon units
has remained an active and challenging goal,[13] research
inspired at least in part by the potential role of these cyclic
molecules in the mechanism of fullerene formation.[14]
One of the oldest and perhaps most general routes toward
Introduction
A great diversity of molecules with conjugated enyne and
polyyne substructures have been proposed or realized,[1
4]
including macrocycles,[5] liquid crystals,[6] oligomers,[7] and
carbon networks.[4,8] In addition to their engaging molecular
structures,many of these carbon rich compounds have unique
electronic,mechanical and structural characteristics,as well as
other desirable materials properties.[4] Extended polyyne
chains with a conjugated skeleton composed only of sp-
hybridized carbon have been sought for many years.[9] Early
work from the groups of Bohlmann,Jones,and Walton
afforded several oligomeric series,with sp-carbon chains as
the synthetic elaboration of an alkyne framework is oxidative
[16]
coupling.[15] This methodology,developed by Glaser,
and
later refined by Eglinton/Galbraith,[17] and Hay,[18] is used to
combine two terminal alkynes via the an intervening CuI/CuII
intermediate. These general methods have been used to make
a range of symmetrical diynes and polyynes,as well as to close
macrocyclic systems. Complementary to this is the Cadiot
Chodkiewicz reaction,[19] which couples a terminal acetylene
and a haloacetylene to give unsymmetrical polyyne products,
also via a cuprate intermediate. The recent development of
numerous palladium catalyzed coupling protocols for alkynes
has greatly expanded the realm of alkyne synthesis,[20]
although their usefulness to date has been predominantly
limited to the terminal functionalization of acetylenes and
diacetylenes.
[10]
ꢀ
long as -(C C)16-,but characterization was limited.
More
recent efforts toward the realization of polyynes and the
penultimate sp-carbon allotrope carbyne,are motivated both
by a fundamental interest in their unique linear,conjugated
framework[11] and a more applied interest in their use as
molecular wires to mediate communication between terminal
[a] Prof. R. R. Tykwinski,S. Eisler,N. Chahal,Dr. R. McDonald
Department of Chemistry
The major limitation to the above methods lies in the fact
that they all require the prior synthesis of a terminal alkyne/
polyyne as one or both of the synthetic precursors to an
extended product. While this is not necessarily a problem for
di- and even triacetylenes,the formation of longer acetylenic
units without terminal functionality almost always affords a
highly unstable species that is difficult or impossible to
manipulate.
University of Alberta
Edmonton,Alberta,T6G 2G2 (Canada)
Fax : (‡1)780492-8231
E-mail: rik.tykwinski@ualberta.ca
Structural data and procedures for the synthesis of compounds 5a j,
6a j, 7a j, 12a,b, 13a,b, 15, 17 19, 21 23,and 25 27; 1H and
13C NMR spectra for all new compounds are available as Supporting
Information at http://www.chemeurj.org/ or from the author.
2542
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
DOI: 10.1002/chem.200204584
Chem. Eur. J. 2003, 9,2542 2550

2542 2550
Several approaches are available that strive to circumvent
the difficulties associated with the instability of terminal
alkynes. For example,methods for the direct coupling of
trialkylsilyl acetylenes have been developed,as have methods
for the in situ generation and reaction of terminal alkynes
under the appropriate coupling conditions.[21,22] Other options
include a variety of protocols in which the polyyne framework
is completed in the final step of the synthesis through either
elimination or extrusion of a suitable functional group. While
these routes have afforded a number of interesting deriva-
tives,in most cases their generality has yet to be established. [23]
Thus,as the prevalence of extended acetylenic structures in
organic chemistry continues to expand,there is a concurrent
need for more versatile synthetic protocols.
Results and Discussion
1,1-Dibromo-2,2-diethynylethenes (7a j) are the backbone
of this alkylidene carbene chemistry,and the general route for
their synthesis based on the adaptation of known methods is
shown in Scheme 2. Alcohols 5 can be made by either of two
H
R
1. nBuLi (2 equiv)
Et2O, –78 °C
Route A
2. ethyl formate
1. nBuLi (1.2 equiv)
Et2O, –78 °C
HO
H
The transformation of 1,1-dihalo-2,2-diarylalkenes 1 into
tolans 3 was originally reported by Fritsch,Buttenberg,and
Wiechell (Scheme 1).[24] This process,which is known to
generally proceed through a carbenoid intermediate 2,has
become a well-established method for alkyne synthesis,and
R1
H
O
H
2.
R1
R2
5a-j
R2
Route B
PCC,
CH2Cl2,
rt
Br
Br
O
CBr4, PPh3,
CH2Cl2, rt
R1
R2
R1
R2
R
R'
7a-j
6a-j
3
4
Br Br
R'
M
R
Br
R'
Scheme 2.
R
1
2
R1
R2
routes: Route A relies on the condensation of two equivalents
of the appropriate lithium acetylide with ethyl formate to
afford symmetrical derivatives 5a,b,f, g,and j.[29] Route B
provides unsymmetrical alcohols 5c e and 5h,i via addition
of the appropriately substituted lithium acetylide into an a,b-
ethynyl aldehyde.[30] The alcohols 5a j can be effectively
oxidized to the corresponding ketones 6a j with either PCC
or BaMnO4. PCC is generally more effective for larger scale
M = Li, MgBr, etc.
Scheme 1.
the general rearrangement now bears their names.[25] Over the
course of the last century,this general transformation has
been successfully applied to numerous systems in which the
migrating group has been an aryl or heteroaryl moiety,a
hydrogen atom,and to a lesser extent an alkenyl or alkyl
group. Conspicuously absent from the above list is the ethynyl
moiety,which to the best of our knowledge has not been
demonstrated to migrate in a Fritsch Buttenburg Wiechell
rearrangement.
reactions (i.e., >1 g),whereas BaMnO provides a more
4
procedurally facile formation of the ketone on smaller scales.
It is worth noting that if the ketone product shows limited
stability,the typically clean reaction mixture can simply be
plugged through silica gel with CH2Cl2,and this solution
carried on directly to the dibromo-olefination step,which is
also conducted in CH2Cl2 (e.g., 5h ! 7h). Vinyl bromides
7a j were then realized via the method of Corey and
Fuchs.[30a,31] This reaction is usually complete in less two
hours,and affords good yields of the desired products,
although reduced chemical stability for some derivatives
resulted in lower yields.
We envisioned an alternative entry into aryl substituted 1,1-
dibromo-olefines via protiodesilylation of the differentially
protected diyne 7c,followed by palladium catalyzed cross-
coupling of the terminal acetylene 8 with an iodo- or
bromoarene [Eq. (1)].[32] The formation of 8 via reaction with
K2CO3 in wet methanol proceeds without problem. Unfortu-
nately,attempts to elaborate 8 under various cross-coupling
conditions with iodoarenes have,to date,been ineffective. For
example,the reaction of 8 with 1-iodonaphthalene using
standard Sonogashira reaction conditions gave only 29%
yield of the desired product 7e. In general,these reactions
provide low yields of the desired product,as well as numerous
We have recently communicated that alkynes do indeed
readily undergo 1,2-shifts in vinylidene carbenoid intermedi-
ates (e.g., 2 where R ˆ R' ˆ -C C-R), in a facile reaction
[26]
ꢀ
that ultimately affords good yields of the desired polyyne
4.[27,28] The requisite 1,1-dibromo-2,2-diethynylethene precur-
sors 1 are easily accessible and can be strategically function-
alized in order to provide polyyne derivatives that would be
difficult or impossible to access by other methods. In general,
the rearrangements proceed without the substantial forma-
tion of by-products,allowing for facile purification and
isolation of the desired product,often without column
chromatography. In this paper,we report a full account of
the synthetic utility of our new method,including the
formation of linear polyynes,extended and highly unsaturated
aryl polyyne building blocks,as well as the solid-state
crystallographic analysis of two highly unsaturated polyyne
derivatives,compounds 20 and 29.
Chem. Eur. J. 2003, 9,2542 2550
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
2543

R. R. Tykwinski et al.
FULL PAPER
side products that make purification challenging. These
results suggest that cross-coupling of the terminal alkyne of
one molecule of 8 with the vinyl bromide moiety of a second
equivalent of 8 effectively competes with the intended cross-
coupling with the iodoarene.
completely surprising,as vinyl lithium intermediates 9a and
9b generated in THF or Et2O have been successfully trapped
with electrophiles at low temperature.[33,34]
Kˆbrich has previously demonstrated that solvent polarity
can play a defining role in the success of the FBW rearrange-
ment.[35] Assuming that the solvating ability of ethereal
solvents was a stabilizing factor that prevented or retarded
collapse of the vinyl lithium intermediate 9a,the rearrange-
ment was attempted in less polar,noncoordinating solvents.
To our gratification,reactions conducted in hexanes,benzene,
and cyclohexene all gave good yields of the triyne 4a
(Table 2).[36] Whereas the reaction in benzene was necessarily
conducted at warmer temperatures (ca. À158C),reaction in
hexanes or cyclohexene was most efficient when initiated at
À788C.
Br
Br Br
Br
I
[PdCl2(PPh3)2],
CuI, NEt3, rt
+
(1)
R
SiiPr3
SiiPr3
7c R = Me3Si
8 R = H
K2CO3,
MeOH
7e 29% (from 7c)
Our initial attempts to induce 1,2-alkyne migration in a
vinylidene carbene/carbenoid species employed dibromo-
olefin 7a (Scheme 3). Using conditions known to facilitate
lithium halogen exchange in this molecule,[33] a THF solution
of 7a was treated with nBuLi at À788C and the solution
Table 2. Yield of triyne 7a as a function of solvent.
Solvent
Yield [%]
THF
Et2O
dioxane
hexane
benzene
cyclohexene
< 5
< 5
< 5
70
80
65
Br
Br
Br
Li
R1
R2
R1
R2
R1
R2
7a-j
9a-j
4a-j
R3
Thus,the optimized general procedure for this process has
been established as the following. Vinyl bromide 7a is
dissolved in rigorously dried hexanes,cooled to À788C,and
1.2 equiv of nBuLi is slowly added over about two minutes.
The reaction is warmed to about À108C over a period of
30 min to 1 h,and then quenched via addition of an aqueous
NH4Cl solution. The product,formed in high yield,can then
be isolated pure following work-up by passing the crude
product through a plug of silica gel.
R4
R1
R2
10a R1 = R2 = SiiPr3; R3 = H; R4 = Br
10b R1 = R2 = SiMe3; R3 = H; R4 = Br
10c R1 = R2 = SiMe3; R3 = H; R4 = nBu
10d R1 = R2 = SiMe3; R3 = R4 = nBu
Scheme 3.
The conditions employed for the successful rearrangement
of 7a have been less reliable with the bis(trimethylsilyl)
derivative 7b.[37] The overall yield for this rearrangement is
typically lower and is also accompanied,unlike other rear-
rangements,by the formation of varying amounts of several
by-products,identified by 1H NMR spectroscopic and MS
analysis as predominantly 10b, c,and d. The rearrangement
reaction with differentially protected 7c,on the other hand,
cleanly gave the triyne 4c. This suggested that perhaps the
presence of a triisopropylsilyl protected alkyne moiety was
somehow important to facilitate the rearrangement. The
rearrangement of 1-naphthyl derivative 7d to the TMS
protected triyne 4d in 70% yield without by-products,
slowly warmed to various temperatures. These reactions did
not,however,afford appreciable amounts of 4a,regardless of
temperature or reaction time. While analysis of these product
mixtures did suggest the formation of trace amounts of 4a,as
detected by mass spectral analysis,the protonated species 10a
was the only identifiable product. Likewise,reactions con-
ducted in Et2O and dioxane were equally unsuccessful
(Table 2). Although disappointing,these results were not
Table 1. Summary of synthetic yields for compounds 4 7.
Cpd R1
R2
5 [%] 6 [%] 7 [%] 4 [%]
[33]
[33]
[33]
a
b
c
d
e
f
iPr3Si
Me3Si
iPr3Si
1-naphthyl Me3Si
1-naphthyl iPr3Si
nBu
n-octyl
iPr3Si
Me3Si
Me3Si
70
50
61
70
62
80
66
[52]
[52]
[30a]
[30a]
ꢀ
however,showed that the presence of the TIPS-C C moiety
[30a]
[30a]
is not a requirement. Comparable to the formation of 4d,the
rearrangement of TIPS protected dibromo-olefin 7e provided
a good yield of triyne 4e. Thus,in addition to pendant
trialkylsilyl functionality,aryl ( 7d, e, h, j) and alkyl (7 f,g, i)
substituents are clearly tolerated by the rearrangement
conditions.[22a,38] Also noteworthy is the formation of more
elaborate aryl tetrayne building block 4h,which features
differential silyl protecting groups that would allow for further
derivatization of this skeleton.
60
55
54
47
54
82
nBu
n-octyl
92[53] 73[54] 40
76[55] 87[55] 54
g
h
Me3Si
iPr3Si
31
53[a]
61
i
j
Me3Si
2-thienyl
nBu
2-thienyl
98
40
57
50
60
47
82
64
[a] Two-step yield from alcohol.
2544
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9,2542 2550

Polyyne Synthesis
2542 2550
In general,the rearrangements in Table 1 are complete
within minutes of n-BuLi addition,as monitored by TLC
analysis. If the reaction is conducted under rigorous anhy-
drous conditions,there is minimal formation of non-polar by-
products. Empirical evidence suggests that lithium halogen
exchange is a more rapid process than quenching of the BuLi
by adventitious water. The presence of water in the reaction
mixture does,however,result in in situ protonation of the
intermediate carbenoid species,to give for example, 10a. This
significantly complicates purification of the desired triyne due
to very similar retention times for the two species on common
chromatographic supports and reemphasizes the need to
maintain anhydrous reagents and reaction conditions.
Complementary to the route outlined above,Scheme 4
demonstrates the facile synthesis of an unsymmetrical tri- and
tetrayne,beginning from the acid chloride 11. Friedel Crafts
acylation of 11 with either bis(trimethylsilyl)acetylene or
bis(trimethylsilyl)butadiyne gave ynones 12a and b,respec-
tively.[39] Dibromo-olefination then afforded 13a and b,and
subsequent rearrangement gave the triyne 14a in 84% yield
and the tetrayne 14b in 64% yield. As acetylenic carboxylic
acids are readily available via condensation of the appropriate
lithium acetylide and CO2,[40] this pathway nicely broadens
the scope of polyyne products potentially accessible using this
methodology.
dimer 15 as a yellow oil,which was easily purified by passing
the reaction mixture through a plug of silica with hexanes. The
moderate yield of 15 likely results from competition from
Castro Stevens coupling,in which the Cu-acetylide cross-
couples with the dibromo-olefin moiety.[41,42] To date,we have
been unable to discover copper-catalyzed homocoupling
conditions that can improve the yield of this or analogous
reactions. Following the general procedure,tetrabromide 15
was rearranged with 2.4 equiv of nBuLi at low temperature.
TLC analysis of the reaction mixture over time shows the
progressive rearrangement of each vinyl bromide moiety,and,
ultimately the 1,3,5,7,9,11-dodecahexayne (16) was the only
nonpolar species observed by TLC analysis. After work-up, 16
was isolated as a yellow/orange solid in 70% overall yield,
representing an impressive 84% yield for each rearrangement
event.
In addition to the synthesis of polyynes such as 16,we
expected that alkyne migration would allow us to explore the
formation of highly unsaturated aryl-polyyne building blocks
that would be difficult to achieve using established palladium
catalyzed,cross-coupling conditions. This concept is demon-
strated in Scheme 6 with hexayne 20. Diol 17 was obtained as
mixture of diastereomers from the condensation of the
bis(lithium acetylide) of 1,4-diethynylbenzene with trimethyl-
silyl propargyl aldehyde. This diol was easily oxidized to the
diketone 18,and dibromo-olefination then provided tetra-
bromide 19. Compound 19 is rather insoluble in hexanes at
À788C,and the rearrangement was therefore initiated at
À448C. Work-up and purification by column chromatography
gave 20 in 50% yield.
O
X
Cl
AlCl3, CH2Cl2,
SiMe3
0 to 25 °C
11
12a X = O, n = 1 47%
12b X = O, n = 2 55%
Me3Si
SiMe3
CBr4, PPh3,
CH2Cl2, rt
SiMe3
n
13a X = CBr2, n = 1 71%
13b X = CBr2, n = 2 48%
HO
PCC, CH2Cl2,
rt, 80%
OH
nBuLi,
hexanes,
17
Me3Si
SiMe3
n
–78 °C
SiMe3
14a n = 1 84%
14b n = 2 64%
nBuLi,
–44 °C,
X
Scheme 4.
hexanes
X
Me3Si
18 X = O
CBr4, PPh3,
CH2Cl2, rt, 85%
Our intention to exploit this method for formation of
extended polyyne chains was explored via the assembly of
dodecahexayne 16 (Scheme 5). The terminal alkyne of
enediyne 8 was oxidatively homocoupled[15,18] to give the
19 X = Br2
Me3Si
SiMe3
20 50%
Scheme 6.
SiiPr3
Br
1. K2CO3
THF/MeOH
Br
8
Tris(lithiation) of 1,3,5-triethynylbenzene in Et2O followed
by condensation with trimethylsilyl propargyl aldehyde gave
the triol 21 in 42% yield (Scheme 7). The PCC oxidation of 21
gave trione 22 as a stable colorless,solid,and subsequent
dibromo-olefination gave hexabromide 23. The three-fold
rearrangement of 23 was initiated at À788C,and the
heterogeneous solution was allowed to warm slowly to
À108C over the course of an hour. Nonayne 24 was isolated
in 35% yield as a creme colored solid,representing an
average of 70% yield for each individual rearrangement.
2. CuI, TMEDA
CH2Cl2
Br
Br
iPr3Si
15 55%
nBuLi,
hexanes,
–78 °C
iPr3Si
SiiPr3
16 70%
Scheme 5.
Chem. Eur. J. 2003, 9,2542 2550
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
2545

R. R. Tykwinski et al.
FULL PAPER
X
dibromo-olefination gave 27 in
a moderate 56% yield. Antici-
pating that the deprotonation
of the terminal acetylene would
compete with lithium halogen
exchange,3.6 equivalents of
nBuLi were utilized to form
heptayne 28,a molecule that
shows reduced stability when
neat. Compound 28 was then
carried on to an oxidative cou-
pling reaction under Hay con-
ditions,to afford the extended
tetradecayne 29. In spite of its
highly unsaturated,polyyne
framework, 29 shows surprising
stability,and could be fully
characterized spectroscopically.
HO
SiMe3
SiMe3
X
HO
PCC, CH2Cl2,
rt, 79%
Me3Si
Me3Si
21
SiMe3
SiMe3
X
HO
22 X = O
CBr4, PPh3,
CH2Cl2, rt, 64%
23 X = Br2
Me3Si
nBuLi,
hexanes,
SiMe3
–44 °C
In particular,the
13C NMR
24 35%
spectrum of this highly sym-
metrical molecule shows the
eight unique resonances for
the sp-hybridized carbons. The
electrospray mass spectrum in
Me3Si
Scheme 7.
the presence of AgOTf distinctly shows the parent signal of
[28‡Ag] at m/z 887.
Whereas compound 24 is stable if left in a dilute hexane
solution under refrigeration (48C),it decomposes over time if
left neat.
‡
The synthesis of triol 21 was always accompanied by the
formation of moderate amounts of diol 25 (Scheme 8),the
result of incomplete reaction of the precursor lithium
acetylide with trimethylsilyl propargyl aldehyde. As the
isolation of 25 was straightforward,it represented an oppor-
tunity to probe the scope of our new methodology. In
particular,we sought to test the sequence of reactions in the
presence of a terminal acetylene,in the pursuit of large carbon
rich polyyne networks. Diol 25 was oxidized to dione 26 and
Solid-state characterization: Crystallization of 20 from a
concentrated hexanes/CH2Cl2 solution via diffusion of MeOH
at 48C afforded single crystals suitable for X-ray crystallo-
graphic analysis. Two crystallographically unique molecules
are present in the unit cell. Both molecules show a slight,
graceful curving of the individual triyne moieties (Figure 1).
The observed bond angles and lengths for both molecules are,
however,unremarkable. The solid state packing of 20 is shown
from two different perspectives in Figure 1,and reveals a high
degree of alignment along both
the crystallographic a- and b
axes. Along the a axis,alternat-
H
H
ing layers,individually com-
posed of only crystallographi-
Me3Si
Me3Si
SiMe3
SiMe3
cally unique molecule A or
PCC, CH2Cl2,
rt, 65%
molecule B,are
observed.
OH
X
OH
X
Within each layer,parallel
alignment of neighboring mol-
ecules is present,and analysis
of packing parameters with re-
spect to topochemical polymer-
ization along either of these
layers demonstrates similar
characteristics for the intermo-
lecular arrangement. This anal-
ysis shows the closest intermo-
lecular distance R1,6 (i.e., be-
tween C1 and C6),at 5.2 and
5.3 ä for molecules A and B,
respectively,is well outside the
desired range of 3.5 4 ä re-
quired for topochemical poly-
25
26 X = O
CBr4, PPh3,
CH2Cl2, rt, 56%
27 X = CBr2
Me3Si
Me3Si
SiMe3
nBuLi,
hexanes,
CuCl, TMEDA,
H
0 °C, RT
–44 °C
28
29 22% (from 27)
Me3Si
Me3Si
SiMe3
Scheme 8.
2546
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9,2542 2550

Polyyne Synthesis
2542 2550
a distance of 3.4 ä and are offset in a manner expected for
face to face p-stacking. Each such ™face-to-face∫ pair of
neighboring molecules is related by a center of inversion,
affording an alternating packing motif to accommodate the
bulk of the trimethylsilyl groups (Figure 2b). While the
carbon atoms of neighboring butadiynyl groups approach at
a distance that might allow for 1,4-addition in a topchemical
polymerization reaction (R1,4 ˆ 4.2 ä),the stacking angle of
f ˆ 708 is well outside of the range necessary for this to occur.
Thus,single crystalline 29 remains reasonably stable at room
temperature for periods of up to several days.
Figure 1. Illustration of crystal packing for compound 20 with the unit cell
boundaries as indicated (hydrogen atoms have been omitted); a) view
direction parallel to the crystallographic a axis,with atom labels for
molecule A,and b) view direction parallel to the crystallographic b axis,
with atom labels for molecule B.
merization.[43,44] The stacking angle, f,between molecules
(ꢁ348 in both cases) as well as the stacking distance, d,(9.1 ä
in both cases) also deviate from their optimal values for 1,6-
addition of f ˆ 278 and d ˆ 7.5 ä,respectively. Thus,polymer-
ization in the solid state along the a-axis is not likely
favorable.
A situation of pseudo-stacking between the crystallograph-
ically independent molecules is seen when viewing down the b
axis. Stacking parameters indicate that from this crystallo-
[43,45]
graphic perspective,a 14,-addition process is possible.
The stacking angle f ˆ 45 is optimal,and two intermolecular
contacts R1,4 ˆ 4.0 ä and R3,6 ꢁ3.9 ä are both in the desired
range (i.e., ꢂ4 ä). The stacking distance d ˆ 5.5 ä is also
reasonable for 1,4-addition. Indeed, warming the crystals to
room temperature for periods of up to an hour results in a
gradual darkening and the formation of an intractable solid.[46]
It seems plausible,therefore,that the parallel alignment of the
molecules in the solid state leads to their demise at ambient
temperature,albeit apparently in a non-regioselective manner
likely caused by competing 1,4- and 3,6-polymerization
processes.
Single crystals of tetradecayne 29 suitable for X-ray analysis
were grown by diffusion of MeOH into a hexanes/CH2Cl2
solution at À108C,and an ORTEP diagram is shown in
Figure 2a. Although positional disorder increases toward the
trimethylsilyl substituted termini of the individual triacety-
lene chains and hampers refinement of this structure,the
overall solid state characteristics of this highly unsaturated
molecule are still clearly evident. The two aryl rings of the
molecule are nearly coplanar,whereas the four 35,-triyne
units gently bend above and below the aryl diyne plane.
Analysis of the solid state packing shows that the aryl rings of
neighboring are within 38 of coplanarity. They are separated at
Figure 2. a) ORTEP drawing for compound 29. b) View of crystal packing
for 29 approximately along the crystal a axis (n-hexane solvent molecules
and hydrogen atoms removed for clarity).
Conclusions
We have outlined the broad synthetic utility of an alkylidene
carbene/carbenoid rearrangement for polyyne formation. The
success of these reactions derives from the seemingly high
migratory aptitude of the alkynyl group in alkylidene carbene/
carbenoid intermediates,which are easily generated via
Chem. Eur. J. 2003, 9,2542 2550
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
2547

R. R. Tykwinski et al.
FULL PAPER
CCDC-197506 (20) and -197507 (29) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crys-
tallographic Data Centre,12 Union Road,Cambridge CB21EZ,UK; (fax:
(‡44)1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk).
lithium halogen exchange between 1,1-dibromo-2,2-diethy-
nylethenes and nBuLi. This rearrangement can be effected on
a number of substrates,and it tolerates silyl,aryl,acetylenic,
and alkyl substitution in the formation of symmetrical and
unsymmetrical polyynes. Most significantly,the ability to
accomplish up to three consecutive/sequential rearrange-
ments within the same molecule in a single step has been
demonstrated and promises to provide a synthetic route to a
wider range of useful and interesting polyynes. The majority
of the new polyyne derivatives show reasonable chemical
stability,and in two cases,the origin of this (in)stability is
explained via single crystal X-ray analysis and examination of
solid state packing.
General procedure for alkyne rearrangements: Unless otherwise noted in
the individual procedures below,a solution of the dibromo-olefin in
hexanes under nitrogen was cooled to À788C. 1.1 1.2 equiv of nBuLi per
dibromo-olefin moiety is slowly added over a period of ca. 2 min. The
reaction mixture turned either a pale yellow or orange in color. Reactions
were allowed to warm to approximately À108C over a period of 0.5 1 h,
unless otherwise noted. TLC analysis indicated that reactions were
generally complete soon after addition of base (<10 min),although
warming of the reaction solution in the TLC capillary tube can influence
these analyses. The reactions were quenched at ca. À58C with an aqueous
NH4Cl solution. Diethyl ether was added (50 mL),the organic layer
separated,washed with aqueous NH 4Cl (2 Â 50 mL),dried (MgSO 4),and
the solvent removed in vacuo. Passing the crude reaction through a silica
plug or flash column chromatography (silica gel) as necessary gave the
desired products.
Experimental Section
1,6-Bis(triisopropylsilyl)-1,3,5-hexatriyne (4a): nBuLi (2.17m in hexanes,
0.17 mL,0.37 mmol) was added to 7a (0.201 g,0.368 mmol) in hexanes
(10 mL) according to the general procedure to produce 4a (0.0989 g,70%)
as an off-white solid. Rf ˆ 0.8 (hexanes). Spectral data were consistent with
those reported by Rubin et al.[23a]
General procedures and methods: Reagents were purchased reagent grade
from commercial suppliers and used without further purification. THF,
Et2O,were distilled from sodium/benzophenone,hexane and benzene
distilled from CaH. Dioxane and Gold label cyclohexene was purchased
from Aldrich. 3-Trimethylsilylpropynal,[40] 1,3,5-triethynylbenzene,[47]
1-ethynylnaphthylene,[48] and 1-triisopropylsilylethynyl-4-trimethylsilyle-
thynylbenzene[49] were made as previously reported. Evaporation and
concentration in vacuo was done at H2O-aspirator pressure. All reactions
were performed in standard,dry glassware under an inert atmosphere of
N2. A positive pressure of N2 was essential to the success of all nBuLi
reactions. Column chromatography: Silica gel 60 (230 400 mesh) from
Rose Scientific Ltd. Thin-layer chromatography (TLC): plastic sheets
covered with silica gel 60 F254 from Macherey-Nagel; visualization by UV
light or KMnO4 stain. M.p.; Gallenkamp apparatus; uncorrected. IR
spectra (cmÀ1): Nicolet Magna-IR 750 (neat) or Nic-Pan IR Microscope
(solids). 1H and 13C NMR: Bruker AM300 or Varian Gemini-300,400,and
500 at rt in CD2Cl2 or CDCl3; solvent peaks (5.27 and 7.24 ppm for 1H and
53.8 and 77.0 ppm,respectively,for 13C) as reference. EI MS (m/z): Kratos
MS50 instrument. Elemental analyses were effected by the Microanalytical
Laboratory at the University of Alberta.
1,6-Bis(trimethylsilyl)-1,3,5-hexatriyne (4b): nBuLi (2.5m in hexanes,
0.13 mL,0.33 mmol) was added to 7b (0.101 g,0.266 mmol) in hexanes
(5 mL) according to the general procedure to produce 4b (0.029 g,50%) as
an off-white solid. Rf ˆ 0.67 (hexanes). Spectral data were consistent with
those reported by Tobe et al.[28]
1-(Triisopropylsilyl)-6-(trimethylsilyl)-1,3,5-hexatriyne (4c): nBuLi (2.17m
in hexanes,0.20 mL,0.43 mmol) was added to 7c (0.200 g,0.432 mmol) in
hexanes (12 mL) according to the general procedure to produce 4c
(0.0802 g,61%). Rf ˆ 0.7 (hexanes). Spectral data were consistent with
those reported by Rubin et al.[23a]
6-(1-Naphthyl)-1-(trimethylsilyl)-1,3,5-hexatriyne (4d): nBuLi (2.5m in
hexane,0.080 mL,0.20 mmol) was added to 7d (0.0687 g,0.159 mmol) at
08C in hexanes (6 mL) according to the general procedure to produce 4d
(0.0303 g,70%) as a clear oil. Rf ˆ 0.43 (hexanes); 1H NMR (300 MHz,
CDCl3,25 8C): d ˆ 8.26 (d, J ˆ 8.3 Hz,1H),7.87 (d, J ˆ 8.2 Hz,1H),7.84
(dd, J ˆ 7.2,1.4 Hz,1H),7.77 (dd, J ˆ 7.2,1.2 Hz,1H),7.55 (m,2H),7.40
X-ray crystallographic studies: Unit cell parameters and intensity data were
obtained on a Bruker PLATFORM/SMART 1000 CCD diffractometer
using graphite-monochromated MoKa radiation (l ˆ 0.71073 ä). Programs
for diffractometer operation,data collection,data reduction and absorp-
tion correction were those supplied by Bruker. The structures were solved
by direct methods using SHELXS-86[50] and refined by full-matrix least
squares on F2 using SHELXL-93.[51] Hydrogen atoms were generated in
idealized positions based on the sp2 or sp3 hybridization of their parent
carbon atoms,and given displacement parameters 120% of the Ueq of their
attached carbon atoms.
(dd, J ˆ 8.3,7.2 Hz,1H),0.22 (s,9H);
258C): d ˆ 134.3,133.1,133.0,130.4,128.6,127.5,126.9,126.0,125.2,118.5,
89.8,88.1,78.9,75.4,68.1,61.7,
À0.5; IR (film): nÄ ˆ 2959,2164,2071,
1505 cmÀ1; MS (70 eV,EI): m/z (%): 272 (91%) [M ],257 (100%) [ M
CH3]; HRMS: calcd for C19H16Si: 272.1021,found 272.1026; elemental
analysis calcd (%) for C19H16Si (272.4): C 83.77,H 5.92; found: C 83.65,H
6.06.
13C NMR (75.5 MHz,APT,CDCl
,
3
‡
‡
À
6-(1-Naphthyl)-1-(triisopropylsilyl)-1,3,5-hexatriyne (4e): nBuLi (2.5m in
hexane,0.19 mL,0.48 mmol) was added to 7e (0.205 g,0.396 mmol) in
hexanes (11 mL) according to the general procedure to produce 4e
(0.0878 g,62%) as an off-white solid. Rf ˆ 0.57 (hexanes); m.p. 34 358C;
1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 8.27 (d, J ˆ 8.1 Hz,1H),7.86 (d, J ˆ
7.9 Hz,1H),7.84 (d, J ˆ 6.5 Hz,1H),7.76 (d, J ˆ 7.2 Hz,1H),7.55 (m,2H),
X-ray crystal data for 20: C24H22Si2; Fw ˆ 366.60; crystal dimensions: 0.38 Â
3
≈
0.31  0.04 mm ; crystal system: triclinic; space group P1 (No. 2), a ˆ
7.1643(15), b ˆ 9.1375(19), c ˆ 17.305(4) ä; a ˆ 98.116(4), b ˆ 92.197(4),
g ˆ 95.230(5)8; Vˆ 1115.3(4) ä3; Z ˆ 2; 1calcd ˆ 1.092 gcmÀ3; 2qmax ˆ 52.848;
absorption correction via Gaussian integration; m ˆ 0.163mmÀ1,range of
transmission factors ˆ 0.9938 0.9402; total number of reflections ˆ 4891;
R1(F) ˆ 0.0699 (2084 observed reflections with Fo2 ꢃ2s(Fo2†), wR2(F2) ˆ
0.1546 for 235 variables and 4153 unique reflections with Fo2 ꢃ À3s(Fo2†;
Tˆ À808C; scan mode: w scans (0.28) (25 s exposures); residual electron
7.40 (dd, J ˆ 8.1,7.8 Hz,1H),1.10 (s,21H);
13C NMR (75.5 MHz,APT,
CDCl3,25 8C): d ˆ 134.3,133.1,132.9,130.3,128.6,127.5,126.8,125.9,125.2,
118.6,89.8,87.5,79.0,75.0,68.5,60.7,18.6,11.4; IR (film):
nÄ ˆ 2943,2182,
2163,2069,1462 cm À1; MS (70 eV,EI): m/z (%): 356 (86%) [M ],313
‡
‡
(100%) [M À iPr]; HRMS: calcd for C25H28Si: 356.1960,found 356.1963.
density ˆ 0.311 and À0.228 eäÀ3
.
5,7,9-Tetradecatriyne (4 f): nBuLi (2.5m in hexane,0.26 mL,0.65 mmol)
was added to 7 f (0.191 g,0.552 mmol) hexanes (16 mL) according to the
general procedure to produce 4 f (0.0821 g,80%) as light yellow oil. Rf ˆ
0.53 (hexanes); 1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 2.26 (t, J ˆ 6.9 Hz,
X-ray crystal data for 29: C55H49Si4; Fw ˆ 822.30; crystal dimensions: 1.00 Â
0.10 Â 0.03 mm3; crystal system: monoclinic; space group P21/c (No. 14),
a ˆ 7.212(2), b ˆ 44.335(12), c ˆ 16.183(4) ä; b ˆ 93.463(5)8; Vˆ 5165
(2) ä3; Z ˆ 4; 1calcd ˆ 1.058 gcmÀ3; 2qmax ˆ 50.008; absorption correction
via a multi-scan model (SADABS); m ˆ 0.147mmÀ1,range of transmission
factors ˆ 0.9956 0.8666; total number of reflections ˆ 21024; R1(F) ˆ
0.1339 (2960 observed reflections with Fo2 ꢃ2s(Fo2†); wR2(F2) ˆ 0.4207
for 457 variables and 9108 unique reflections with Fo2 ꢃ À 3s(Fo2†; Tˆ
À808C; scan mode: w scans (0.28) (25 s exposures); residual electron
4H),1.49 (m,4H),1.40 (m,4H),0.84 (t,
J ˆ 7.2 Hz,6H); 13C NMR
(75.5 MHz,APT,CDCl 3,25 8C): d ˆ 79.3,65.7,60.4,30.2,22.0,19.1,13.5; IR
(cast): nÄ ˆ 2958,2216,1465 cm À1; MS (70 eV,EI): m/z (%): 186 (100%)
‡
[M ]; HRMS: calcd for C14H18: 187.1487,found 187.1445.
8,10,12-Eicosatriyne (4g): nBuLi (2.5m in hexane,0.20 mL,0.50 mmol) was
added to 7g (0.194 g,0.422 mmol) in hexanes (12 mL) according to the
general procedure to produce 4g (0.0835 g,66%) as a light brown oil. Rf ˆ
density ˆ 1.060 and À0.460 eäÀ3
.
2548
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9,2542 2550

Polyyne Synthesis
2542 2550
CDCl3,25 8C): d ˆ 89.5,87.1,62.8,62.7,62.5,61.3,18.6,11.4; IR (CHCl
3
0.59 (hexanes); 1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 2.31 (t, J ˆ 7.0 Hz,
cast): nÄ ˆ 2944,2158,2127,2067,2030,1462 cm À1; MS (70 eV,EI): m/z (%):
4H),1.52 (m,4H),1.40 (m,4H),1.25 (m,16H),0.86 (m,6H);
13C NMR
‡
‡
458 (42) [M ],415 (100) [ M À iPr]; HRMS: calcd for C30H42Si2: 458.2825,
(75.5 MHz,APT,CDCl 3,25 8C): d ˆ 79.4,65.8,60.4,31.9,29.2,29.1,28.9,
‡
found 458.2834 [M ].
28.2,22.7,19.4,14.1; IR (cast): nÄ ˆ 2926,2855,2216,1466 cm À1; MS (70 eV,
‡
Bis-1,4-[6-(trimethylsilyl)-1,3,5-hexatriynyl]benzene (20): nBuLi (2.5m in
hexane,0.24 mL,0.60 mmol) was added to 19 (0.173 g,0.252 mmol) at
À448C in hexanes (15 mL) according to the general procedure to produce
20 (0.0463 g,50%) as a pale yellow solid. Rf ˆ 0.42 (hexanes); m.p. 1808C
(decomp.); 1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 7.44 (s,4H),0.20 (s,
18H); 13C NMR (75 MHz,CDCl 3,25 8C): d ˆ 133.0,122.2,90.2,87.9,77.2,
EI): m/z (%): 298 (36%) [M ]; HRMS: calcd for C22H34: 298.2661,found
298.2662.
[1-(Trimethylsilyl)-1,3,5-hexatriynyl]-[(4-triisopropylsilyl)ethynyl]benzene
(4h): nBuLi (2.5m in hexanes,0.06 mL,0.15 mmol) was added to
7h
(0.0578 g,0.103 mmol) in hexanes (5 mL) according to the general
procedure to produce 4h (0.0254 g,61%) as
a
yellow oil. Rf ˆ 0.5
75.9,68.4,61.2,
À0.5; IR (microscope): nÄ ˆ 2956,2167,2075 cm À1; MS
(hexanes); 1H NMR (500 MHz,CDCl 3,25 8C): d ˆ 7.41 (m,4H),1.11 (s,
21H),0.21 (s,9H); 13C NMR (125 MHz,APT,CDCl 3,25 8C): d ˆ 132.7,
131.9,124.9,120.5,106.2,94.5,89.6,88.0,76.4,76.0,67.8,61.4,18.7,11.4,
‡
‡
(70 eV,EI): m/z (%): 366 (98) [M ],351 (100) [ M À CH3]; HRMS: calcd
‡
for C24H22Si2: 366.1260; found 366.1265 [M ].
À0.4; IR (CH2Cl2 cast): nÄ ˆ 2958,2891,2154,2076,1506 cm À1; MS (70 eV,
Tris-1,3,5-[6-(trimethylsilyl)-1,3,5-hexatriynyl]benzene (24): nBuLi (2.5m
in hexane,0.25 mL,0.63 mmol) was added to 23 (0.174 g,0.176 mmol) in
hexanes (20 mL) according to the general procedure to produce 24
(0.0317 g,35%) as a creme colored solid. Rf ˆ 0.5 (hexanes); m.p. 1608C;
1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 7.65 (s,3H),0.23 (s,27H); 13C NMR
(75 MHz,APT,CDCl 3,25 8C): d ˆ 138.1,122.8,90.9,87.6,76.3,74.1,68.2,
60.9, À0.6; IR (CH2Cl2 cast): nÄ ˆ 2960,2168,2074,1575 cm À1; MS (70 eV,
‡
‡
EI): m/z (%): 402 (57%) [M ],359 (100%) [ M À iPr]; HRMS: calcd for
C26H34Si2: 402.2199,found 402.2204.
1-(Trimethylsilyl)-1,3,5-decatriyne (4i): nBuLi (2.5m in hexanes,0.20 mL,
0.50 mmol) was added to 7i (0.1484 g,0.4100 mmol) in hexanes (10 mL)
according to the general procedure to produce 4i (0.0677 g,82%) as a light
yellow oil. Rf ˆ 0.54 (hexanes); 1H NMR (400 MHz,CDCl 3,25 8C): d ˆ 2.27
‡
EI): m/z (%): 510 (100) [M ]; HRMS: calcd for C33H30Si3: 510.1655,found
(t, J ˆ 7.0 Hz,2H),1.49 (m,2H),1.38 (m,2H),0.89 (t,
J ˆ 7.3 Hz,3H),0.16
‡
510.1648 [M ].
(s,9H); 13C NMR (100 MHz,APT,CDCl 3,25 8C): d ˆ 88.3,85.4,81.0,65.4,
62.5,59.9,30.0,21.9,19.1,13.5, À0.5; IR (CH2Cl2 cast): nÄ ˆ 2960,2874,2211,
1-Ethynyl-3,5-bis[6-(trimethylsilyl)-1,3,5-hexatriynyl]benzene (28): nBuLi
2167,2079 cm À1; MS (70 eV,EI): m/z (%): 202 (31%) [M ],187 (100%)
‡
(2.5m in hexanes,0.25 mL,0.63 mmol) was added to
27 (0.151 g,
‡
0.0.213 mmol) in hexanes (25 mL) at À448C according to the general
procedure. Following work-up,the reaction mixture was passed through a
short column (silica gel,hexanes) to give the crude product 28 (0.06 g,ca.
70%) as a relatively unstable compound if taken to dryness,but of
sufficient purity (>95%) to be taken on directly to the next step: Rf ˆ 0.38
(hexanes); 1H NMR (400 MHz,CDCl 3,25 8C): d ˆ 7.58 (s,3H),3.12 (s,
1H),0.22 (s,18H); 13C NMR (125 MHz,CDCl 3,APT,25 8C): d ˆ 136.9,
[M À CH3]; HRMS: calcd for C13H18Si: 202.1178,found 202.1180.
1,6-Bis(2-thienyl)-1,3,5-hexatriyne (4j): nBuLi (2.5m in hexanes,0.08 mL,
0.20 mmol) was added to 7j (0.066 g,0.17 mmol) in hexanes (5 mL)
according to the general procedure to produce 4j (0.0259 g,64%) as a
yellow solid. Rf ˆ 0.42 (hexanes); m.p. 58 598C; 1H NMR (400 MHz,
CDCl3): d ˆ 7.38 (dd, J ˆ 1.2,3.9 Hz,2H),7.32 (dd, J ˆ 1.2,5.1 Hz,2H),6.98
(dd, J ˆ 3.9,5.1 Hz,2H); 13C NMR (100 MHz,APT,CDCl 3,25 8C): d ˆ
123.5,122.1,89.9,87.7,80.9,79.5,75.9,74.1,67.8,60.9,53.4,
À0.5; IR (CDCl3
135.6,129.6,127.3,121.3,78.6,72.7,68.5; IR (CH
2Cl2 cast): nÄ ˆ 3114,2187,
cast): nÄ ˆ 3299,2960,2169,2075,1578 cm À1; MS (EI,70 eV) m/z (%): 390.1
‡
1433 cmÀ1; MS (70 eV,EI): m/z (%): 238 (100) [M ]; HRMS: calcd for
‡
‡
(39) [M ],73.0 (100) [Me 3Si ]; HRMS: calcd for C26H22Si2: 390.1260,found
C14H6S2: 237.9911,found 237.9907.
390.1258.
3-(Bromomethylidene)-1,5-bis(triisopropylsilyl)penta-1,4-diyne
(10a):
1,4-[Bis-1-[3,5-bis[6-(trimethylsilyl)-1,3,5-hexatriynyl]phenyl]butadiyne (29):
Compound 28 (0.0295 g,0.0755 mmol) was added to a solution of CuI
(0.026 g,0.14 mmol) and TMEDA (1 mL) in dichloromethane (35 mL).
The reaction was followed by TLC and was completed within 30 minutes.
Compound 29 was isolated by column chromatography (silica gel,hexanes)
as a white solid (0.0092 g,31%). Rf ˆ 0.31 (hexanes); 1H NMR (400 MHz,
CD2Cl2,25 8C): d ˆ 7.65 (m,6H),0.23 (s,36H); 13C NMR (100 MHz,APT,
CD2Cl2,25 8C): d ˆ 137.9,137.7,123.2,122.7,90.8,87.6,80.0,76.2,75.4,74.2,
68.1,60.8, À0.6; IR (CH2Cl2 cast): nÄ ˆ 2959,2168,2074,1574 cm À1; MS
nBuLi (1.6m in hexanes,0.15 mL,0.24 mmol) was added to 7a (0.106 g,
0.194 mmol) in THF or Et2O (6 mL) at À788C,and the mixture was
warmed to varying temperatures and then quenched with aqueous NH4Cl.
Dependent upon the final temperature of the reaction,varying amounts of
10a were produced,with the yield decreasing substantially for reactions
quenched at higher temperatures (>08C): Rf ˆ 0.85 (hexanes); 1H NMR
(400 MHz,CDCl 3): d ˆ 6.91 (s,1H),1.09 (s,21H),1.06 (s,21H);
13C NMR
(100 MHz,APT,CDCl 3,25 8C): d ˆ 123.1,112.9,102.3,101.4,98.9,92.4,
18.5,11.2; IR (CH 2Cl2 cast): nÄ ˆ2943,2866,2149,1463 cm À1; MS (70 eV,
‡
(ESI,nitromethane,AgOTf added): m/z (%): 887 (100) [M ‡Ag].
‡
‡
EI): m/z (%): 468 (24) [M ],425 (100) [ M À iPr].
1-(Trimethylsilyl)-6-phenyl-1,3,5-hexatriyne (14a): nBuLi (2.5m in hex-
anes,0.15 mL,0.38 mmol) was added to
13a (0.145 g,0.380 mmol) in
hexanes (7 mL) according to the general procedure to produce 14a
(0.0711 g,84%) as a clear oil. Rf ˆ 0.49 (hexanes); 1H NMR (400 MHz,
CDCl3): d ˆ 7.50 (d, J ˆ 6.9 Hz,2H),7.36 (d, J ˆ 7.3 Hz,1H),7.31 (t, J ˆ
7.3 Hz,2H),0.21 (s,9H); 13C NMR (100 MHz,APT,CDCl 3,25 8C): d ˆ
Acknowledgement
Financial support was provided by the University of Alberta,the Natural
Sciences and Engineering Research Council of Canada,and Petro-Canada
(Young Innovator Award to RRT).
133.1,129.8,128.5,120.8,89.0,88.0,76.8,74.3,66.8,61.6,
À0.5; IR (CH2Cl2
cast): nÄ ˆ 2960,2174,2076,1490 cm À1; MS (70 eV,EI): m/z (%): 222 (35)
‡
‡
[M ],207 (100) [ M À CH3]; HRMS: calcd for C15H14Si: 222.0865,found
222.0865.
1-(Trimethylsilyl)-8-phenyl-1,3,5,7-octatetrayne (14b): nBuLi (2.5m in
hexanes,0.13 mL,0.33 mmol) was added to 13b (0.112 g,0.275 mmol) in
hexanes (7 mL) according to the general procedure to produce 14b
(0.0432 g,64%) as a clear oil. Rf ˆ 0.57 (hexanes); 1H NMR (400 MHz,
CDCl3): d ˆ 7.51 (dd, J ˆ 7.1,1.5 Hz,2H),7.39 (tt, J ˆ 7.4,1.5 Hz,1H),7.32
(m,2H),0.21 (s,9H); 13C NMR (100 MHz,APT,CDCl 3,25 8C): d ˆ 133.2,
[1] F. Diederich, Chem. Commun. 2001,219.
[2] Modern Acetylene Chemistry (Eds.: P. J. Stang,F. Diederich),VCH,
Weinheim, 1995.
[3] Top. Curr. Chem. 1999, Vol. 201 (Ed.: A. de Meijere),Springer,Berlin.
[4] F. Diederich,Y. Rubin, Angew. Chem. 1992, 104,1123; Angew. Chem.
Int. Ed. Engl. 1992, 31,1101.
[5] Y. Tobe,R. Furukawa,M. Sonoda,T. Wakabayashi,
2001, 113,4196; Angew. Chem. Int. Ed. 2001, 40,4072.
[6] S. Hˆger,V. Enkelmann,K. Bonrad,C. Tschierske,
130.0,128.6,120.4,88.8,87.9,76.9,74.4,67.2,64.0,62.2,61.8,
À0.6; IR
(CH2Cl2 cast): nÄ ˆ 2961,2195,2132,2059,1491 cm À1; MS (70 eV,EI): m/z
Angew. Chem.
‡
‡
(%): 246 (46) [M ],231 (100) [ M À CH3]; HRMS: calcd for C17H14Si:
246.0865,found 246.0863.
Angew. Chem.
1,12-Bis(triisopropylsilyl)-1,3,5,7,9,11-dodecahexayne (16): nBuLi (2.5m in
hexane,0.22 mL,0.55 mmol) was added to 15 (0.198 g,0.254 mmol) in
hexanes (16 mL) according to the general procedure to produce 16
(0.0816 g,70%) as a yellow/orange solid. Rf ˆ 0.85 (hexanes); m.p. 78
808C; 1H NMR (300 MHz,CDCl 3,25 8C): d ˆ 1.07; 13C NMR (75 MHz,
2000, 112,2356; Angew. Chem. Int. Ed. 2000, 39,2268; S. K. Collins,
G. P. A. Yap,A. G. Fallis, Org. Lett. 2000, 2,3189.
[7] R. E. Martin,U. Gubler,J. Cornil,M. Balakina,C. Boudon,C.
Bosshard,J.-P. Gisselbrecht,F. Diederich,P. G¸nter,M. Gross,J.-L.
¬
Bredas, Chem. Eur. J. 2000, 6,3622
Chem. Eur. J. 2003, 9,2542 2550
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
2549

R. R. Tykwinski et al.
FULL PAPER
[8] M. M. Haley,W. B. Wan,in
Advances in Strained and Interesting
[28] A similar carbene approach to polyynes has been reported: Y. Tobe,
N. Iwasa,R. Umeda,M. Sonoda, Tetrahedron Lett. 2001, 42,5485.
[29] H. Hauptmann,M. Mader, Synthesis 1978,307.
[30] a) J. Anthony,A. M. Boldi,Y. Rubin,M. Hobi,V. Gramlich,C. B.
Knobler,P. Seiler,F. Diederich, Helv. Chim. Acta 1995, 78, 13; b) B. A.
Kulkarni,S. Chattopadhyay,A. Chattopadhyay,V. R. Mamdapur, J.
Org. Chem. 1993, 58,5964; c) D. H. Wadsworth,S. M. Geer,M. R.
Detty, J. Org. Chem. 1987, 52,3662; d) L. J. P. van Amsterdam,J.
Lugtenburg, Chem. Commun. 1982,946.
Organic Molecules, Vol. 8 (Ed.: B. Halton),JAI Press,New York, 2000,
p. 1 41; U. H. F. Bunz,Y. Rubin,Y. Tobe, Chem. Soc. Rev. 1999,107.
[9] H. Hopf, Classics in Hydrocarbon Synthesis,Wiley-VCH,Weinheim,
2000.
[10] R. Eastmond,T. R. Johnson,D. R. M. Walton, Tetrahedron 1972, 28,
4601; R. Eastmond,D. R. M. Walton, Tetrahedron 1972, 28,4591;
E. R. H. Jones,H. H. Lee,M. C. Whiting, J. Chem. Soc. 1960,3483; F.
Bohlmann, Chem. Ber. 1953, 86,657.
[11] T. Gibtner,F. Hampel,J.-P. Gisselbrecht,A. Hirsch,
Chem. Eur. J.
[31] E. J. Corey,P. L. Fuchs, Tetrahedron Lett. 1972,3769.
[32] K. Sonogashira,Y. Tohda,N. Hagihara, Tetrahedron Lett. 1975,4467.
[33] T. Lange,J.-D. van Loon,R. R. Tykwinski,M. Schreiber,F. Diederich,
Synthesis 1996,537.
2002, 8,408; R. J. Lagow,J. J. Kampa,H.-C. Wei,S. L. Battle,J. W.
Gegne,D. A. Laude,C. J. Harper,R. Bau,R. C. Stevens,J. F. Haw,E.
Munson, Science 1995, 267,362; G. Schermann,T. Grˆsser,F. Hampel,
A. Hirsch, Chem. Eur. J. 1997, 3,1105.
[34] K. S. Feldman,C. K. Weinreb,W. J. Youngs,J. D. Bradshaw,
J. Am.
[12] J. Stahl,J. C. Bohling,E. B. Bauer,T. B. Peters,W. Mohr,J. M. Martin-
Alvarez,F. Hampel,J. A. Gladysz, Angew. Chem. 2002, 114,1951;
Angew. Chem. Int. Ed. 2002, 41,1871; R. Dembinski,T. Bartik,B.
Bartik,M. Jaeger,J. A. Gladysz, J. Am. Chem. Soc. 2000, 122,810; A.
Sakurai,M. Akita,Y. Moro-oka, Organometallics 1999, 18,3241.
[13] Y. Tobe,T. Fujii,H. Matsumoto,K. Tsumuraya,D. Noguchi,N.
Chem. Soc. 1994, 116,9019; J.-D. van Loon,P. Seiler,F. Diederich,
Angew. Chem. 1993, 105,1235; Angew. Chem. Int. Ed. Engl. 1993, 32,
1187.
[35] G. Kˆbrich,P. Buck,in Chemistry of Acetylenes (Ed.: H. G. Viehe),
Marcel Dekker,New York, 1969,Chapter 2.
[36] It is worth noting that no cyclopropylidene by-product resulting from
addition of an intermediate carbene/carbenoid species to the olefin
moiety of the cyclohexene was detected.
Nakagawa,M. Sonoda,K. Naemura,Y. Achiba,T. Wakabayashi,
Am. Chem. Soc. 2000, 122,1762; F. Diederich,Y. Rubin,O. L.
Chapman,N. S. Goroff, Helv. Chim. Acta 1994, 77,1441; F. Diederich,
Nature 1994, 369,199.
J.
[37] Our initial efforts were unsuccessful in effecting the formation of 4b
(ref. [26]).
[14] N. S. Goroff, Acc. Chem. Res. 1996, 29,77.
[15] P. Siemsen,R. C. Livingston,F. Diederich, Angew. Chem. 2000, 112,
2740; Angew. Chem. Int. Ed. 2000, 39,2633.
[38] C. Mukai,N. Miyakoshi,M. Hanaoka, J. Org. Chem. 2001, 66,5875.
[39] D. R. M. Walton,F. Waugh, J. Organomet. Chem. 1972, 37,45.
[40] L. Brandsma, Preparative Acetylenic Chemistry,Elsevier,Amsterdam,
1988.
[16] C. Glaser, Ann. Chem. Pharm. 1870, 154,137.
[17] G. Eglinton,A. R. Galbraith, Chem. Ind. (London) 1956,737.
[18] A. S. Hay, J. Org. Chem. 1962, 27,3320
[19] W. Chodkiewicz, Ann. Chim. (Paris) 1957, 2,819.
[20] Metal-Catalyzed Cross-Coupling Reactions (Eds.: F. Diederich,P. J.
Stang),Wiley-VCH,Weinheim, 1997.
[41] R. D. Stephens,C. E. Castro, J. Org. Chem. 1963, 28,3313.
[42] T. Kauffmann, Angew. Chem. 1974, 86,321; Angew. Chem. Int. Ed.
Engl. 1974, 13,291.
[43] R. H. Baughman,K. C. Yee, J. Polym. Sci. Macromol. Rev. 1978, 13,
219.
[21] Y. Nishihara,K. Ikegashira,K. Hirabayashi,J. Ando,A. Mori,T.
Hiyama, J. Org. Chem. 2000, 65,1780; Y. Hatanaka,T. Hiyama, Synlett
1991,845.
[44] V. Enkelmann, Chem. Mater. 1994, 6,1337.
[45] H. B‰ssler, Adv. Polym. Sci. 1984, 63,1.
[46] Surprisingly,crystallization of compound 20 from a concentrated
[22] a) M. A. Heuft,S. K. Collins,G. P. A. Yap,A. G. Fallis, Org. Lett. 2001,
3,2883; b) M. L. Bell,R. C. Chiechi,C. A. Johnson,D. B. Kimball,
A. J. Matzger,W. B. Wan,T. J. R. Weakley,M. M. Haley, Tetrahedron
2001, 57,3507.
[23] a) Y. Rubin,S. S. Lin,C. B. Knobler,J. Anthony,A. M. Boldi,F.
Diederich, J. Am. Chem. Soc. 1991, 113,6943; b) Y. Tobe,T. Fujii,K.
Naemura, J. Org. Chem. 1994, 59,1236; c) A. Orita,N. Yoshioka,P.
Struwe,A. Braier,A. Beckmann,J. Otera, Chem. Eur. J. 1999, 5,1355.
[24] P. Fritsch, Liebigs Ann. Chem. 1894, 279,319; W. P. Buttenberg,
Liebigs Ann. Chem. 1894, 279,324; H. Wiechell, Liebigs Ann. Chem.
1894, 279,337.
[25] W. Kirmse, Angew. Chem. 1997, 109,1212; Angew. Chem. Int. Ed.
Engl. 1997, 36,1164; P. J. Stang, Chem. Rev. 1978, 78,383; H. D.
Hartzler,in Carbenes, Vol. 2 (Eds.: R. A. Moss,M. Jones,Jr.),Wiley,
New York, 1975,p. 43 100; G. Kˆbrich, Angew. Chem. 1972, 84,557;
Angew. Chem. Int. Ed. Engl. 1972, 11,473.
hexanes solution affords a microcrystalline solid that is stable
indefinitely. Crystals of this apparent polymorph are,unfortunately,
unsuitable for crystallographic analysis.
[47] M. Uno,P. H. Dixneuf, Angew. Chem. 1998, 110,1822; Angew. Chem.
Int. Ed. 1998, 37,1714.
[48] I. R. Butler,C. Soucy-Breau, Can. J. Chem. 1991, 69,1117.
[49] O. Lavastre,J. Plass,P. Bachmann,S. Guesmi,C. Moinet,P. H.
Dixneuf, Organometallics 1997, 16,184.
[50] G. M. Sheldrick, Acta Crystallogr. 1990, A46,467.
[51] G. M. Sheldrick, SHELXL-93. Program for crystal structure deter-
mination,University of Gˆttingen,Gˆttingen (Germany), 1993.
[52] H. Hauptmann, Tetrahedron 1976, 32,1293.
[53] R. Mahrwald,S. Quint, Tetrahedron 2000, 56,7463.
[54] T. Metler,A. Uchida,S. I. Miller, Tetrahedron 1968, 24,4285.
[55] G. L. Isele,K. Scheib, Chem. Ber. 1975, 108,2312.
[26] S. Eisler,R. R. Tykwinski, J. Am. Chem. Soc. 2000, 122,10736.
[27] A. L. K. Shi Shun,E. T. Chernick,S. Eisler,R. R. Tykwinski, J. Org.
Chem. 2003, 68,1339 1347; E. T. Chernick,S. Eisler,R. R. Tykwinski,
Tetrahedron Lett. 2001, 42,8575.
Received: November 19,2002 [F4584]
2550
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9,2542 2550