Synthesis of unsymmetrically substituted 1,3-butadiynes and 1,3,5-hexatriynes via alkylidene carbenoid rearrangements

Article abstract of DOI:10.1021/jo026481h

Unsymmetrically substituted 1,3-butadiynes and 1,3,5-hexatriynes are synthesized in four steps from commercially available aldehydes or carboxylic acids. The key step in this process involves a Fritsch-Buttenberg-Wiechell rearrangement, in which an alkylidene carbenoid intermediate subsequently rearranges to the desired polyyne. This rearrangement proceeds under mild conditions, and it is tolerant of a range of functionalities. In general, the procedurally facile formation of the dibromoolefinic precursors, in combination with the effectiveness of the rearrangement step, makes this procedure an attractive alternative to traditional methods for di- and triyne synthesis that utilize palladium or copper catalysis.

Full text of DOI:10.1021/jo026481h

Syn th esis of Un sym m etr ica lly Su bstitu ted 1,3-Bu ta d iyn es a n d
1,3,5-Hexa tr iyn es via Alk ylid en e Ca r ben oid Rea r r a n gem en ts
Annabelle L. K. Shi Shun, Erin T. Chernick, Sara Eisler, and Rik R. Tykwinski*
Department of Chemistry, University of Alberta, Edmonton AB T6G 2G2, Canada
rik.tykwinski@ualberta.ca
Received September 25, 2002
Unsymmetrically substituted 1,3-butadiynes and 1,3,5-hexatriynes are synthesized in four steps
from commercially available aldehydes or carboxylic acids. The key step in this process involves a
Fritsch-Buttenberg-Wiechell rearrangement, in which an alkylidene carbenoid intermediate
subsequently rearranges to the desired polyyne. This rearrangement proceeds under mild conditions,
and it is tolerant of a range of functionalities. In general, the procedurally facile formation of the
dibromoolefinic precursors, in combination with the effectiveness of the rearrangement step, makes
this procedure an attractive alternative to traditional methods for di- and triyne synthesis that
utilize palladium or copper catalysis.
In tr od u ction
Galbraith,9 or related protocols, which proceed via oxi-
dative homocoupling of terminal acetylenes with Cu(I)/
Cu(II) catalysis.10 These conditions are not suitable,
however, for the synthesis of unsymmetrically substi-
tuted 1,3-butadiynes. The oxidative coupling of two or
more different acetylenic precursors affords a mixture of
products, and separation is invariably tedious and dif-
ficult. A more substantial challenge is encountered in the
formation of both symmetrical and unsymmetrical 1,3,5-
hexatriynes via oxidative coupling because the reactivity
(acidity) of the two precursors, a terminal acetylene and
diacetylene, differ appreciably. Thus, attempts to as-
semble the triyne skeleton via oxidatively coupling these
two groups usually leads first to homocoupling of the
diacetylene (to give the symmetrical tetrayne) followed
by diyne formation via homocoupling of the acetylene.10a,11
The 1,3-butadiynyl and 1,3,5-hexatriynyl moieties are
versatile and useful building blocks in organic synthesis
that have been exploited for their rigid and conjugated
nature.1 Butadiynes, in particular, have been widely
utilized as substructures in the formation of new photonic
materials,2 oligomers and polymers,3 macrocycles,4 and
supramolecular scaffolds.5 Diynes and triynes have a rich
history as precursors for single-crystal polydiacetylene
formation via topochemical polymerization reactions, the
only method known to give such materials.6 Furthermore,
di- and triynes are, perhaps somewhat surprisingly, quite
common constituents of natural products.7
Symmetrically substituted 1,3-butadiynes are rela-
tively straightforward to synthesize using Hay,8 Eglinton/
(1) (a) Modern Acetylene Chemistry; Stang, P. J ., Diederich, F., Eds.;
VCH: Weinheim, Germany, 1995. (b) Niedballa, U., Ed. Houben-Weyl;
Thieme: Stuttgart, 1977; Vol. 5/2a, pp 913-962.
(7) (a) J ones, E. R. H. Proc. Chem. Soc., London 1960, 199-210. (b)
So¨rensen, N. A. Proc. Chem. Soc., London 1961, 98-110. (c) Bohlmann,
F.; Bornowski, H.; Arndt, C. Fortsch. Chem. Forsch. 1962, 4, 138-
272. (d) Bu’Lock, J . D. Prog. Org. Chem. 1964, 6, 86-134. (e)
Bohlmann, F. In Chemistry of Acetylenes; Viehe, H. G., Ed.; Marcel
Dekker: New York, 1969; Chapter 14, pp 977-986. (f) Bohlmann, F.;
Burkhardt, H.; Zdero, C. Naturally Occurring Acetylenes; Academic
Press: New York, 1973. (g) Hansen, L.; Boll, P. M. Phytochemistry
1986, 25, 285-293. (h) Nakao, Y.; Uehara, T.; Matunaga, S.; Fusetani,
N.; van Soest, R. W. M. J . Nat. Prod. 2002, 65, 922-924. (i) Zhang,
H.; Lu, Z.; Tan, G. T.; Qiu, S.; Farnsworth, N. R.; Pezzuto, J . M.; Fong,
H. S. Tetrahedron Lett. 2002, 43, 973-977. (j) Zgoda, J . R.; Freyer, A.
J .; Killmer, L. B.; Porter, J . R. J . Nat. Prod. 2001, 64, 1348-1349. (k)
Alam, N.; Bae, B. H.; Hong, J .; Lee, C. O.; Im, K. W.; J ung, J . H. J .
Nat. Prod. 2001, 64, 1059-1063. (l) Youssef, D. T. A.; Yoshida, W. Y.;
Kelly, M.; Scheuer, P. J . J . Nat. Prod. 2000, 63, 1406-1410.
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Cheng, L.-T.; Perry, J . W. J . Am. Chem. Soc. 1991, 113, 7658-7666.
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Bunz, U. H. F.; Rubin, Y.; Tobe, Y. Chem. Soc. Rev. 1999, 107-119.
(c) Diederich, F.; Rubin, Y. Angew. Chem., Int. Ed. Engl. 1992, 31,
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10.1021/jo026481h CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/23/2003
J . Org. Chem. 2003, 68, 1339-1347
1339

Shi Shun et al.
CHART 1
The chemistry of alkylidene carbenes and carbenoid
species has a rich and diverse history. Dependent upon
reaction conditions and substrate, a free carbene (1) can
undergo addition reactions to olefins, bond insertion
reactions, or, as shown in eq 1, rearrangements to afford
an alkyne (3). In the case of carbenoid species 2, the latter
mode of reactivity, rearrangement to an alkyne product,
ordinarily dominates, a reaction deemed the Fritsch-
Buttenberg-Wiechell (FBW) rearrangement when R )
R′ ) aryl.18 This transformation has been a well-utilized
technique for the formation of tolans.19,20 We have
recently reported the modification of this method and
have demonstrated that it is suitable for the formation
of polyynes via alkyne migration in carbene/carbenoid
intermediates.21,22 These initial studies suggested that,
in addition to the well-established propensity for aryl and
olefin migration in an alkylidene carbenoid species,19b 1,2-
alkyne migrations could also be quite successful. As a
result, we envisioned 1,1-dibromoolefins as precursors to
di- and triynes 3 as shown in Chart 1, route C. This
reaction would involve a sequence of lithium halogen
exchange with a suitable 1,1-dibromoolefin to give the
carbene/carbenoid intermediate, followed by rearrange-
ment to the desired polyyne.
Thus, homocoupling is generally an inefficient method
for the synthesis of triynes.
As a result of the challenges outlined above for homo-
coupling reactions, the cross-coupling of terminal acety-
lenes with alkynyl bromides or iodides, the Cadiot-
Chodkiewicz coupling (Chart 1, route A),12 has often been
useful for accessing unsymmetrical 1,3-diynes13 as well
as symmetrical and unsymmetrical 1,3,5-hexatriynes.14
Such molecules have also been realized via the pal-
ladium-catalyzed cross-coupling reaction of terminal
alkynes with aryl halides or triflates, such as the Sono-
gashira reaction (Chart 1, route B).15 The predominant
limitation of these and related methods in the synthesis
of di- and triynes,16 however, is that they all require the
prior synthesis of a terminal alkyne for one or both of
the coupling partners. This situation becomes problem-
atic in the case of terminal diynes or triynes, which are
quite often unstable to isolation and must therefore be
generated and utilized in situ.17
We now report the successful synthesis of functional-
ized, unsymmetrical 1,3-butadiynes23 and 1,3,5-hexatriynes
via this method.24 Beginning with commercially available
(18) (a) Fritsch, P. Liebigs Ann. Chem. 1894, 272, 319-323. (b)
Buttenberg, W. P. Liebigs Ann. Chem. 1894, 272, 324-337. (c) Wiechell,
H. Liebigs Ann. Chem. 1894, 272, 337-344.
(19) (a) Kirmse, W. Angew. Chem., Int. Ed. Engl. 1997, 36, 1164-
1170. (b) Stang, P. J . Chem. Rev. 1978, 78, 383-405. (c) Hartzler, H.
D. In Carbenes; Moss, R. A., J ones, M., J r., Eds.; Wiley and Sons: New
York, 1983; Vol. 2, pp 43-100. (d) Ko¨brich, G. Angew. Chem., Int. Ed.
Engl. 1972, 11, 473-485. (e) Ko¨brich, G. Angew. Chem., Int. Ed. Engl.
1965, 4, 49-68.
(11) Bohlmann, F.; Scho¨nowsky, H.; Inhoffen, E.; Grau, G. Chem.
Ber. 1964, 97, 794-800.
(12) (a) Chodkiewicz, W.; Cadiot, P. C. R. Hebd. Seances Acad. Sci.
1955, 241, 1055-1057. (b) Chodkiewicz, W. Ann. Chim. (Paris) 1957,
2, 819-869.
(20) For recent examples of the FBW rearrangement, see: (a) Rezaei,
H.; Yamanoi, S.; Chemla, F.; Normant, J . F. Org. Lett. 2000, 2, 419-
421. (b) Creton, I.; Rezae¨ı, H.; Marek, I.; Normant, J . F. Tetrahedron
Lett. 1999, 40, 1899-1902. (c) Mourie`s, V.; Waschbu¨sch, R.; Carran,
J .; Savignac, P. Synthesis 1998, 271-274. (d) Sato, H.; Isono, N.;
Miyoshi, I.; Mori, M. Tetrahedron 1996, 52, 8143-8158. (e) Kawase,
T.; Darabi, H. R.; Uchimiya, R.; Oda, M. Chem. Lett. 1995, 499-500.
(21) Eisler, S.; Tykwinski, R. R. J . Am. Chem. Soc. 2000, 122,
10736-10737.
(13) Inter alia, see: (a) Montierth, J . M.; DeMario, D. R.; Kurth, M.
J .; Schore, N. E. Tetrahedron 1998, 54, 11741-11748. (b) Steffen, W.;
Laskoski, M.; Collins, G.; Bunz, U. H. F. J . Organomet. Chem. 2001,
630, 132-138. (c) Bohlmann, F.; Arndt, C.; Bornowski, H.; Herbst, P.
Chem Ber. 1960, 93, 981-987. (d) Bohlmann, F.; J astrow, H.; Erting-
shausen, G.; Kramer, D. Chem. Ber. 1964, 97, 801-808.
(14) Inter alia, see: (a) Ziessel, R.; Suffert, J .; Youinou, M.-T. J . Org.
Chem. 1996, 61, 6535-6546. (b) Bohlmann, F.; Herbst, P. Chem. Ber.
1958, 91, 1631-1642. (c) Bohlmann, F.; Herbst, P.; Gleinig, H. Chem.
Ber. 1961, 94, 948-957. (d) Bohlmann, F.; Laser, J . Chem. Ber. 1966,
99, 1834-1836. (d) Bohlmann, F.; Kap-Herr, W.; J ente, R.; Grau, G.
Chem. Ber. 1966, 99, 2091-2095.
(22) The migration of an alkyne in a free carbene has recently been
reported; see: Tobe, Y.; Iwasa, N.; Umeda, R.; Sonoda, M. Tetrahedron
Lett. 2001, 42, 5485-5488.
(23) For other examples of unsymmetrical diyne syntheses, see: (a)
Alami, M.; Ferri, F. Tetrahedron Lett. 1996, 37, 2763-2766. (b) Kwon,
J . H.; Lee, S. T.; Shim, S. C.; Hoshino, M. J . Org. Chem. 1994, 59,
1108-1114. (c) Aitken, R. A.; Seth, S. J . Chem. Soc., Perkin Trans. 1
1994, 2461-2466. (d) Blanco, L.; Helson, H. E.; Hirthammer, M.;
Mestdagh, H.; Spyroudis, S.; Vollhardt, K. P. C. Angew. Chem., Int.
Ed. Engl. 1987, 26, 1246-1247. (e) Ziegler, C. B., J r.; Harris, S. M.;
Baldwin, J . E. J . Org. Chem. 1987, 52, 443-446. (f) Fritzsche, U.;
Hu¨nig, S. Tetrahedron Lett. 1972, 4831-4834. (g) Lu, W.; Zheng, G.;
Aisa, H. A.; Cai, J . Tetrahedron Lett. 1998, 39, 9521-9522. (h) Zheng,
G.; Lu, W.; Cai, J . J . Nat. Prod. 1999, 62, 626-628. (i) Nishihara, Y.;
Ikegashira, K.; Hirabayashi, K.; Ando, J .; Mori, A.; Hiyama, T. J . Org.
Chem. 2000, 65, 1780-1787. (j) Nishihara, Y.; Ikegashira, K.; Mori,
A.; Hiyama, T. Tetrahedron Lett. 1998, 39, 4075-4078. For another
example of unsymmetrical triyne synthesis, see: Gardner, J . N.; J ones,
E. R. H.; Leeming, P. R.; Stephenson, J . S. J . Chem. Soc. 1960, 691-
697.
(15) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 50, 4467-4470. See also ref 10d, Chapter 5.
(16) (a) Negishi, E.; Hata, M.; Xu, C. Org. Lett. 2000, 2, 3687-3689.
(b) Godt, A. J . Org. Chem. 1997, 62, 7471-7474. (c) Kitamura, T.;
Tanaka, T.; Taniguchi, H.; Stang, P. J . J . Chem. Soc., Perkin Trans. 1
1991, 2892-2893. (d) Wityak, J .; Chan, J . B. Synth. Commun. 1991,
21, 977-979. (e) Amatore, C.; Blart, E.; Geneˆt, J . P.; J utand, A.;
Lemaire-Audoire, S.; Savignac, M. J . Org. Chem. 1995, 60, 6829-6839.
(f) Kende, A. S.; Smith, C. A. J . Org. Chem. 1988, 53, 2655-2657. (g)
Miller, J . A.; Zweifel, G. Synthesis 1983, 128-130.
(17) (a) Bell, M. L.; Chiechi, R. C.; J ohnson, C. A.; Kimball, D. B.;
Matzger, A. J .; Wan, W. B.; Weakley, T. J . R.; Haley, M. M. Tetrahedron
2001, 57, 3507-3520. (b) Heuft, M. A.; Collins, S. K.; Yap, G. P. A.;
Fallis, A. G. Org. Lett. 2001, 3, 2883-2886.
(24) For a preliminary account of these results, see: Chernick, E.
T.; Eisler, S.; Tykwinski, R. R. Tetrahedron Lett. 2001, 42, 8575-8578.
1340 J . Org. Chem., Vol. 68, No. 4, 2003

Synthesis of 1,3-Butadiynes and 1,3,5-Hexatriynes
SCHEME 1a
TABLE 1. Isola ted Yield s for Com p ou n d s 5-8
a
Reagents and conditions: (a) Et2O, -78 °C; (b) PCC, Celite,
molecular sieves (4 Å), CH2Cl2, rt; (c) PPh3 (2 equiv), CBr4, CH2Cl2
at rt or C6H6 at reflux; (d) n-BuLi, -78 to -40 °C, hexanes.
aryl or vinyl aldehydes and carboxylic acids (or acid
chlorides), these polyynes are achieved in four facile
steps, with the carbenoid rearrangement proceeding
under mild conditions and generally in good to excellent
yields. As this method has not been successfully executed
in all cases, however, the scope and limitation of this
protocol are also discussed.
Resu lts a n d Discu ssion
The synthetic sequence toward unsymmetrically sub-
stituted 1,3-butadiynes begins with condensation of a
slight excess of the appropriate lithium acetylide with
an aryl carboxaldehyde in Et2O at -78 °C (Scheme 1).25
As a result of the slight excess of the acetylide, complete
reaction with the aldehyde can generally be effected, and
the resultant alcohols 5 can be isolated pure and in high
yield following aqueous workup (Table 1).
Oxidation from alcohol 5 to ketone 6 is normally
accomplished with PCC at rt in CH2Cl2. Reaction times
are less than 1 h for most derivatives, and concentration
of the reaction mixture, followed by filtration through a
short plug of silica, affords the crude ketone. The ketone
is normally of sufficient purity to be carried on to the
subsequent dibromoolefination step. The ketones can,
however, be isolated pure by column chromatography, as
demonstrated for a number of the examples in Table 1.
The oxidation of several alcohols was particularly difficult
with PCC (e.g., 5k , 5n , 5o). As a result, BaMnO4 was
employed as the oxidant,26 with more satisfactory results.
As this reaction is done in CH2Cl2, filtration of the
reaction solution through Celite to remove the insoluble
barium salts affords a CH2Cl2 solution of the ketone
suitable to be carried on to the dibromoolefination step
without additional purification or manipulation. In two
cases, the aniline and pyridine derivatives 5g and 5j, we
were unable to successfully complete the oxidation pro-
cedure due to the chemical instability of these substrates.
a
Using PCC in CH2Cl2. b Using BaMnO4 in CH2Cl2. c Yield over
two steps from alcohol, without isolation of intermediate ketone.
d
(25) A similar route has been utilized by others; inter alia, see: (a)
Brown, R. F. C.; J ackson, W. R.; McCarthy, T. D. Tetrahedron 1994,
50, 5469-5488. (b) Baldoli, C.; Del Buttero, P.; Licandro, E.; Maiorana,
S.; Papagni, A.; Torchio, M. Tetrahedron Lett. 1993, 34, 7943-7946.
(26) Lange, T.; van Loon, J .-D.; Tykwinski, R. R.; Schreiber, M.;
Diederich, F. Synthesis 1996, 537-550.
Dibromoolefination reaction in CH2Cl2 at rt. e Dibromoolefination
reaction in C6H6 at 80 °C.
The well-established dibromoolefination method using
PPh3/CBr4 was employed to provide derivatives 7.27 For
J . Org. Chem, Vol. 68, No. 4, 2003 1341

Shi Shun et al.
SCHEME 2a
sterically unhindered ketones, the dibromoolefinations
can generally be completed at rt in CH2Cl2 in 1-2 h. For
ketones 6b, 6f, and 6k , however, reactions were sluggish
at rt in CH2Cl2 and were therefore carried out in benzene
under reflux. In all cases, the dibromoolefinic products
are considerably less polar than the ketone precursors,
as well as any byproducts of the reaction, and can
therefore be quickly and easily purified by column
chromatography.
During the course of this study, it became apparent
that the dibromoolefination step is the weakest link in
this synthetic sequence. The first 1,3-butadiyne deriva-
tives that we targeted were terminated at one end with
a trimethylsilyl group (entries a -m , Table 1) since this
alkyne protecting group nicely allows for further syn-
thetic elaboration of the resultant diynes. In these cases,
reasonable to good yields of the desired dibromoolefinic
products could be achieved, whether beginning with
either the pure ketone or the crude product directly from
the oxidation reaction. As it turns out, however, the
presence of the trimethylsilyl group also appears to play
a significant role in the success of the dibromoolefination
reactions. In cases where this group has been replaced
by either an alkyl or aryl moiety, the yields from the
dibromoolefination reaction are dramatically reduced
(e.g., 7p -r ), and in some cases we have been unable to
effect this transformation at all (entries 7n and 7o). To
date, this remains the predominant limitation of our
methodology.28
The conversion of the dibromoolefins to the desired
diynes 8 has been consistently more successful in hex-
anes, as opposed to more polar solvents such as Et2O or
THF.29,30 Thus, diyne formation is effected by the drop-
wise addition of n-BuLi to a hexanes solution of 7 cooled
to -78 °C. The mixture is subsequently warmed to ca.
-20 °C over 0.5-1 h to ensure complete rearrangement
of the carbenoid intermediate31 and then quenched by the
addition of an aqueous NH4Cl solution. If strictly anhy-
drous reaction conditions have been maintained during
the rearrangement, the diyne is generally the sole
product as observed by TLC analysis.32 The diynes can
thus be isolated pure, in good to excellent yields, by
passing the concentrated reaction mixture through a plug
of silica to remove any polar baseline material. As
a
Reagents and conditions: (a) Me3SiCtCSiMe3, AlCl3, CH2Cl2,
0 to 25 °C; (b) PPh3 (2 equiv), CBr4, CH2Cl2; (c) n-BuLi, hexanes,
-78 to -40 °C.
demonstrated in Table 1, the carbenoid rearrangement
process allows a range of pendant groups to be appended
to the diyne skeleton, including aromatic hydrocarbon
(8a ,b), electron-rich and -poor aryl (8c-f,k ,p ),33 het-
eroaryl (8h ,i,q,r ), alkyl (8p -r ), and vinyl (8l,m ) func-
tionalities.
Scheme 2 outlines an alternate pathway to aryl 1,3-
diynes that exploits readily available carboxylic acid
chlorides. Friedel-Crafts acylation of aryl or vinyl acid
chlorides with bis(trimethylsilyl)acetylene easily afforded
ketones 9a -f in good to excellent yields (Table 2).34
Dibromoolefination of 9a -f under standard conditions
generated 10a -f. Subjecting dibromides to n-BuLi at -78
°C according to the standard protocol described above
afforded 11a -e in good to excellent yields. This route
allowed formation of functionalized diacetylenes such as
the azo diyne 11c, trimethoxyarene 11d , and thienyl-
terminated enediyne 11e. Frustratingly, rearrangement
of butadienyl derivative 11f was unsuccessful, regardless
of the conditions employed. For this substrate, unreacted
dibromoolefin 10f was recovered, along with the product
derived from protonation of the intermediate carbenoid
species, but no diyne could be detected in the reaction
mixture. In view of the facile rearrangement of vinyl
dibromides 7l, 7m , and 10e, the inability to effect an
analogous rearrangement on 10f is surprising and re-
mains unexplained.
(27) (a) Corey, E. J .; Fuchs, P. L. Tetrahedron. Lett. 1972, 3769-
3772. (b) Posner, G.; Loomis, G. L.; Sawaya, H. S. Tetrahedron Lett.
1975, 1373-1376. (c) Ramirez, F.; Desai, N. B.; McKelvie, N. J . Am.
Chem. Soc. 1962, 84, 1745-1747. (d) Neidlein, R.; Winter, M. Synthesis
1998, 1362-1366. (e) Anthony, J .; Boldi, A. M.; Rubin, Y.; Hobi, M.;
Gramlich, V.; Knobler, C. B.; Seiler, P.; Diederich, F. Helv. Chim. Acta
1995, 78, 13-45.
(28) A recent report offers one potential solution to this problem;
see: Rezaei, H.; Normant, J . F. Synthesis 2000, 109.
(29) Ko¨brich had extensively studied solvent effects in aryl- and
alkyl-substituted alkylidene carbenes; see: Ko¨brich, G.; Buck, P. In
Chemistry of Acetylenes; Viehe, H. G., Ed.; Marcel Dekker: New York,
1969; Chapter 2.
The traditional difficulties encountered in the synthesis
of unsymmetrical triacetylenes led us to extend our
general protocol in this direction, as outlined in Scheme
3. Friedel-Crafts acylation of the appropriate acyl chlo-
ride with 1,4-bis(trimethylsilyl)-1,3-butadiyne provided
diynones 12a -f (Table 3). Ketones 12a -c, with pendant
aryl functionality, showed somewhat limited stability.
Although they could be isolated, decomposition was
(30) A full investigation of the mechanistic aspects of these reactions
is under way and will be published in due course. Preliminary evidence
suggests that collapse of the carbenoid intermediate is consistent with
that expected on the basis of the results of Curtin and Bothner-By,
which is to say that the group that is trans to the bromide atom in the
intermediate 2 is the one that migrates; see: Curtin, D. Y.; Flynn, E.
W.; Nystrom, R. F. J . Am. Chem. Soc. 1958, 90, 4599. Bothner-By, A.
A. J . Am. Chem. Soc. 1955, 77, 3293. See also ref 20a.
(31) Using TLC to monitor these reactions is problematic, as
warming of the sample in the capillary tube used for TLC application
can lead to the inaccurate observation that the reaction has reached
completion.
(32) Experimental evidence suggests that lithium-halogen exchange
is faster than quenching of the BuLi by adventitious water in the
reaction medium. As a result, any water that is present results in
protonation of the carbenoid intermediate, which severely complicates
purification due to very similar retention times on chromatographic
supports.
(33) The low yield for 8c results from the presence of the o-alkoxy
substituent; see: Ko¨brich, G.; Trapp, H. Chem. Ber. 1966, 99, 680-
688.
(34) (a) Walton, D. R. M.; Waugh, F. J . Organomet. Chem. 1972,
37, 45-56. (b) Suzuki, R.; Tsukuda, H.; Watanabe, N.; Kuwatani, Y.;
Ueda, I. Tetrahedron 1998, 54, 2477-2496.
1342 J . Org. Chem., Vol. 68, No. 4, 2003

Synthesis of 1,3-Butadiynes and 1,3,5-Hexatriynes
TABLE 2. Isola ted Yield s for Com p ou n d s 9-11
TABLE 3. Isola ted Yield s for Com p ou n d s 12-14
a
Yield over two steps from acid chloride, without isolation of
intermediate ketone.
SCHEME 3a
SCHEME 4a
a
Reagents and conditions: (a) Me3SiCtCsCtCSiMe3, AlCl3,
CH2Cl2, 0 to 25 °C; (b) PPh3 (2 equiv), CBr4, CH2Cl2; (c) n-BuLi,
hexanes, -78 to -40 °C.
a
Reagents and conditions: (a) PCC, Celite, molecular sieves
(4 Å), CH2Cl2, rt; (b) PPh3 (2 equiv), CBr4, CH2Cl2, rt; (c) n-BuLi,
hexanes, -78 to -40 °C.
always observed when manipulations were carried out
under ambient conditions. Thus, these compounds were
expeditiously carried on to the dibromoolefination step
in CH2Cl2 at rt, following workup. Although the dibro-
moolefinic products 13a -c are relatively stable, overall
yields for these derivatives remained low for the two-step
process. Conversely, enediynones 12d -f were consider-
ably more stable and could be isolated in good yields and
characterized in all cases. The enhanced stability of
12d -f also afforded increased yields for dibromoolefins
13d -f, which were isolated in 40-75% yield. Carbenoid
rearrangement of 13a -f to triynes 14a -f was accom-
plished in the same manner as outlined for diyne forma-
tion above. Yields from these rearrangements were
moderate to excellent, with olefinic derivatives consis-
tently formed in higher yields. It should be noted that
unlike the formation of azo diyne 11c, which proceeded
without isomerization of the azo moiety, triyne 14c was
isolated and characterized as a mixture of its E- and
Z-stereoisomers.
PCC, followed by dibromoolefination, gave the tetrabro-
mide 17 in 57% yield over the two steps from 15. Subject-
ing 17 to 2.4 equiv of n-BuLi afforded 1,4-bis(4-trimeth-
ylsilyl-1,3-butadiynyl)benzene (18) in 87% yield as a
colorless, quite stable, crystalline solid. The formation of
18 nicely demonstrates the ability to scale-up the rear-
rangement protocol: this reaction produced nearly 2 g
of 18.
Single crystals of 18 were easily grown from a concen-
trated solution in hexanes at 4 °C. X-ray crystallographic
analysis of 18 shows the butadiynyl segments to be
nearly linear, as expected for an sp-hybridized carbon
system (Figure 1). The most notable feature of the solid-
state structure is the parallel solid-state alignment of
neighboring molecules, in a manner potentially suitable
for topochemical polymerization. Analysis of the packing
parameters shows that the stacking angle between
neighboring molecules is θ ) 49°, near the optimal value
of 45° required for a 1,4-polymerization process.35 The
stacking distance at d ) 5.9 Å and distance between
reacting atoms R ) 4.4 Å (C7 to C4 of the neighboring
molecule), however, are both outside the ideal values of
This general sequence of reactions is applicable to the
assembly of larger, extended polyyne systems as outlined
in Scheme 4. Diol 15 is easily produced in 88% yield as
a mixture of stereoisomers via the condensation of Lis
CtCsSiMe3 with terephthaldehyde. Oxidation with
J . Org. Chem, Vol. 68, No. 4, 2003 1343

Shi Shun et al.
4-tert-butylbenzoyl chloride, followed by dibromoolefina-
tion in CH3CN. Although the octyloxy side chains and
the tert-butyl end groups greatly enhanced the solubility
of 20, yields from the dibromoolefination step remained
frustratingly low (∼20%), regardless of the conditions
employed. Solubility did, however, have a dramatic effect
on the yield of the rearrangement step, and the highly
fluorescent, stable tetrayne 22 was produced in nearly
quantitative yield from tetrabromide 20.
F IGURE 1. ORTEP drawing (20% probability level) of 18
demonstrating solid-state packing. Selected bond lengths (Å)
and angles (deg): C(1)-C(4) 1.432(3), C(4)-C(5) 1.196(3),
C(5)-C(6) 1.377(3), C(6)-C(7) 1.208(3); C(1)-C(4)-C(5) 178.8-
(2), C(4)-C(5)-C(6) 178.7(2), C(5)-C(6)-C(7) 179.6(2), C(6)-
C(7)-Si 178.57(19).
Con clu sion s
In summary, the carbenoid rearrangement described
herein provides a facile route to a range of aryl diyne
and triyne systems. This synthetic route offers several
attractive features versus more commonly employed
palladium coupling methods including (1) the wide range
of commercially available aryl and vinyl aldehydes and
carboxylic acid precursors, (2) tolerance of a range of
chemical functionalities, and (3) generally rapid reaction
times and easy purification/isolation that often allow for
all four transformations of the di- or triyne synthesis to
be accomplished within a single day. The most significant
limitation of this method, to date, is the variability
encountered in the conversion of ynones into the requisite
dibromoolefinic precursors. Whereas this step generally
proceeds in good yield for derivatives of trimethylsilyl-
substituted substrates, other end groups are not as well
tolerated.
SCHEME 5
Exp er im en ta l Section
d ≈ 5 Å and R < 4 Å, respectively. Thus, the observed
stability of 18 in the solid state can be attributed, at least
in part, to the inability of the compound to undergo
topochemical polymerization.
Gen er a l In for m a tion . Reagents were purchased reagent
grade from commercial suppliers and used without further
purification. Et2O and benzene were distilled from sodium/
benzophenone ketyl, and hexanes and dichloromethane were
distilled from CaH2 immediately prior to use. 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 performed in standard,
dry glassware under an inert atmosphere of N2. For simplicity,
the coupling constants of the aryl protons for para-substituted
phenyl groups have been reported as pseudo-first-order, even
though they are second-order spin systems. For mass spectral
analyses, low-resolution data are provided in cases where M+
is not the base peak; otherwise, only high-resolution data are
provided.
Gen er a l P r oced u r e for Alcoh ol F or m a tion . To trim-
ethylsilylacetylene (1.23 g, 12.5 mmol, 1.25 equiv) in Et2O (50
mL) at -78 °C was added n-BuLi (2.5 M in hexanes, 4.8 mL,
12 mmol, 1.2 equiv). After the mixture was stirred for 30 min,
the appropriate aldehyde (10 mmol, 1 equiv) in Et2O (5 mL)
was added. The reaction mixture was slowly warmed to ca.
-10 °C until the reaction was judged complete by TLC
analysis. The reaction was quenched with saturated aq NH4-
Cl at -78 °C, and the organic layer was washed with brine (2
× 50 mL) and dried (MgSO4). The resulting alcohol could
generally be used without further purification.
The syntheses of two functionalized, extended polyyne
systems are described in Scheme 5. Tetrabromide 19
derives from the condensation of the bis(lithium) acetyl-
ide of 1,4-(diethynyl)benzene with 2-thiophene carbox-
aldehyde, followed by PCC oxidation and dibromoolefi-
nation under standard conditions. The tetrabromide 19
was isolated in 33% yield, over two steps from the diol,
with the moderate yield primarily the result of the
problematic isolation of the relatively insoluble solid 19
from the reaction mixture. Rearrangement of tetrabro-
mide 19 to tetrayne 21 was accomplished by the addition
of n-BuLi at -78 °C and then allowing the reaction
mixture to warm to approximately -10 °C to increase
the solubility of 19 and facilitate the rearrangement. The
rigid tetrayne 21 proved to be a nearly insoluble solid,
which hampered isolation and purification. Nonetheless,
it could be obtained in 24% yield as a yellow solid that
has been identified by its 1H NMR spectrum, which
demonstrates its symmetrical structure, and by mass
spectrometry, which shows the expected parent signal
at m/z 338.
Gen er a l P r oced u r e for Keton e F or m a tion via Oxid a -
tion Usin g P CC. To the appropriate alcohol (4 mmol) in CH2-
Cl2 (50 mL) were added sequentially Celite (equal amount by
mass to that of PCC), molecular sieves (4 Å, equal amount by
mass to that of PCC), and PCC (5 mmol, 1.25 equiv). After
being stirred at rt until the reaction was judged complete by
TLC analysis, the solution was filtered through a plug of silica
(CH2Cl2), and the solvent was evaporated to give the corre-
sponding ketone. The ketone was of sufficient purity to be
carried directly to the dibromoolefination step without further
The tetrabromide 20 is obtained as a stable oil via the
two-step sequence of the Friedel-Crafts acylation of 1,4-
di(octyloxy)-2,5-bis(trimethylsilylethynyl)benzene with
(35) Shirakawa, H.; Masuda, T.; Takeda, K. In The Chemistry of
Triple-bonded Functional Groups; Patai, S., Ed.; J ohn Wiley and
Sons: New York, 1994; Vol. 2, Suppl. 2, pp 992-994.
1344 J . Org. Chem., Vol. 68, No. 4, 2003

Synthesis of 1,3-Butadiynes and 1,3,5-Hexatriynes
purification, or could be isolated pure by column chromatog-
raphy (hexanes/CH2Cl2, 1:1).
[4-(2-Me t h oxyp h e n yl)-1,3-b u t a d iyn yl]t r im e t h ylsi-
la n e (8c). Dibromoolefin 7c (82.0 mg, 0.211 mmol) was reacted
with n-BuLi (0.10 mL, 2.5 M in hexanes, 0.25 mmol) as per
the general procedure to give diyne 8c (20.6 mg, 43%) as a
yellow oil: Rf ) 0.7 (hexanes/CH2Cl2, 1:1); IR (CH2Cl2 cast)
2959, 2836, 2204, 2103, 1594, 1273 cm-1; 1H NMR (500 MHz,
CDCl3) δ 7.43 (m, 1H), 7.30 (m, 1H), 6.86 (m, 2H), 3.86 (s, 3H),
0.21 (s, 9H); 13C NMR (125 MHz, APT, CDCl3) δ 161.6, 134.5,
130.7, 120.4, 110.6, 91.0, 88.1, 77.9, 73.3, 55.8, -0.2 (one
Gen er a l P r oced u r e for Keton e F or m a tion via Oxid a -
tion Usin g Ba Mn O4. To the appropriate alcohol (4 mmol) in
CH2Cl2 (50 mL) was added barium manganate (3 equiv). After
being stirred at rt until the reaction was judged complete by
TLC analysis, the solution mixture was filtered through a pad
of Celite. The solvent was evaporated to give the corresponding
ketone.
Gen er al P r ocedu r e for Keton e For m ation via Fr iedel-
Cr a fts Acyla tion . The formation of 9a -f and 12a -f was
accomplished as reported for similar derivatives.34 Com-
mercially available acid chlorides were used except for 4-phe-
nylazobenzoyl chloride, 3-(2-thienyl)acryloyl chloride, and
sorbyl chloride, which were made from the commercially
available carboxylic acid.
Gen er a l P r oced u r e for Acid Ch lor id e F or m a tion . To
the appropriate carboxylic acid (1 equiv) was added thionyl
chloride (6 equiv). After the mixture was stirred for 24 h, the
excess thionyl chloride was evaporated, and the acid chloride
was used directly in the next step without further purification.
Gen er a l P r oced u r e for Dib r om oolefin F or m a t ion .
Literature procedures were followed as referenced.27 In some
cases, and to date unexplained, reactions conducted under
reported conditions would fail to go to completion using the
normal amounts of PPh3 and CBr4. In these cases, an ad-
ditional equivalent of both PPh3 and CBr4 would be added to
force the reaction to completion.
Gen er a l P r oced u r e for Diyn e F or m a tion .36 Unless
otherwise noted, the following procedure was followed. To the
appropriate dibromoolefin (0.368 mmol) in dry hexanes (10
mL) at -78 °C was added dropwise over 10 min 1.1-1.2 equiv
of n-BuLi (0.15 mL, 2.5 M in hexanes, 0.38 mmol). The mixture
was warmed to approximately -40 °C for 30 min, recooled to
-78 °C, and quenched with a saturated aq solution of NH4Cl.
Et2O was added (∼50 mL), and the organic layer was sepa-
rated, washed with a saturated aq solution of NH4Cl, and dried
over magnesium sulfate. Solvent removal in vacuo and passing
the residue through a short plug of silica gel with the solvent
system detailed for each product afforded the desired diyne.
If necessary, additional purification could be achieved via flash
column chromatography.
coincident peak not observed); EI HRMS m/z calcd for C14H16
-
OSi (M+) 228.0971, found 228.0967.
[4-(3-Me t h oxyp h e n yl)-1,3-b u t a d iyn yl]t r im e t h ylsi-
la n e (8d ). Dibromoolefin 7d (152 mg, 0.392 mmol) was reacted
with n-BuLi (0.16 mL, 2.5 M in hexanes, 0.40 mmol) as per
the general procedure to give diyne 8d (67.3 mg, 75%) as a
colorless oil: Rf ) 0.8 (hexanes/CH2Cl2, 1:1); IR (CHCl3 cast)
3004, 2959, 2207, 2102, 1596, 1574, 1251 cm-1; 1H NMR (300
MHz, CDCl3) δ 7.20 (dd, J ) 8.2, 7.7 Hz, 1H), 7.07 (ddd, J )
1.1, 1.4, 7.7 Hz, 1H), 6.98 (dd, J ) 1.4, 2.6 Hz, 1H), 6.91 (ddd,
J ) 8.2, 2.6, 1.1 Hz, 1H), 3.77 (s, 3H), 0.22 (s, 9H); 13C NMR
(75 MHz, APT, CDCl3) δ 159.2, 129.5, 125.2, 122.3, 117.2,
116.1, 90.7, 87.7, 76.6, 73.9, 55.2, -0.4; EI HRMS m/z calcd
for C14H16OSi (M+) 228.0971, found 228.0966. Anal. Calcd for
C
14H16OSi: C, 73.63; H, 7.06. Found: C, 73.69; H, 6.99.
[4-(4-Me t h oxyp h e n yl)-1,3-b u t a d iyn yl]t r im e t h ylsi-
la n e (8e). Dibromoolefin 7e (139 mg, 0.358 mmol) was reacted
with n-BuLi (0.15 mL, 2.5 M in hexanes, 0.38 mmol) as per
the general procedure to give diyne 8e (67.2 mg, 82%) as a
yellow oil. Spectral data were consistent with those reported
by Haley.37
[4-(4-n -Bu t oxyp h e n yl)-1,3-b u t a d iyn yl]t r im e t h ylsi-
la n e (8f). Dibromoolefin 7f (200 mg, 0.464 mmol) was reacted
with n-BuLi (0.19 mL, 2.5 M in hexanes, 0.48 mmol) as per
the general procedure to give diyne 8f (99 mg, 79%) as a yellow
solid: mp 68-69 °C; Rf ) 0.9 (hexanes/Et2O, 4:1); IR (CH2Cl2
cast) 2956, 2940, 2871, 2203, 2101, 1602, 1508, 1257 cm-1; 1H
NMR (400 MHz, CDCl3) δ 7.42 (d, J ) 8.8 Hz, 2H), 6.83 (d, J
) 8.8 Hz, 2H), 3.96 (t, J ) 7.2 Hz, 2H), 1.76 (m, 2H), 1.48 (m,
2H), 0.96 (t, J ) 7.4 Hz, 3H), 0.22 (s, 9H); 13C NMR (100 MHz,
APT, CDCl3) δ 160.1, 134.3, 114.7, 113.0, 89.8, 88.2, 77.2, 73.0,
67.9, 31.2, 19.2, 13.8, -0.3; MS (EI, 70 eV) m/z 270.1 (M+, 78),
199.1 ([M - C4H8 - CH3]+, 100); EI HRMS m/z calcd for C17H22
-
OSi (M+) 270.1440, found 270.1436.
[4-(1-Naph th yl)-1,3-bu tadiyn yl]tr im eth ylsilan e (8a). Di-
bromoolefin 7a (757 mg, 1.85 mmol) was reacted with n-BuLi
(1.0 mL, 2.5 M in hexanes, 2.5 mmol) as per the general
procedure to give diyne 8a (430 mg, 93%) as a yellow oil: Rf
) 0.3 (hexanes); IR (CH2Cl2 cast) 3058, 2959, 2199, 2098, 1585,
[4-(2-F u r yl)-1,3-bu ta d iyn yl]tr im eth ylsila n e (8h ). Di-
bromoolefin 7h (126 mg, 0.362 mmol) was reacted with n-BuLi
(0.15 mL, 2.5 M in hexanes, 0.38 mmol) as per the general
procedure to give diyne 8h (37.1 mg, 54%) as a light yellow oil
that slowly decomposes, even if kept refrigerated: Rf ) 0.9
(hexanes/CH2Cl2, 1:1); IR (CH2Cl2 cast) 2960, 2201, 2104, 1251
cm-1; 1H NMR (300 MHz, CD2Cl2) δ 7.43 (dd, J ) 2.0, 0.1 Hz,
1H), 6.77 (dd, J ) 3.3, 0.7 Hz, 1H), 6.43 (dd, J ) 3.3, 0.7 Hz,
1H), 0.23 (s, 9H); 13C NMR (75 MHz, APT, CD2Cl2) δ 145.4,
136.5, 119.1, 111.6, 94.6, 87.2, 79.2, 66.4, -0.4; MS (EI, 70
eV) m/z 188.1 (M+, 44), 173.0 ([M - CH3]+, 100); EI HRMS
m/z calcd for C11H12OSi (M+) 188.0658, found 188.0662.
[4-(2-Th ien yl)-1,3-bu ta d iyn yl]tr im eth ylsila n e (8i). Di-
bromoolefin 7i (582 mg, 1.60 mmol) was reacted with n-BuLi
(0.77 mL, 2.5 M in hexanes, 1.93 mmol) as per the general
procedure to give diyne 8i (298 mg, 91%) as a light brown oil
that slowly decomposes, even if kept refrigerated: Rf ) 0.9
(CH2Cl2/hexanes, 1:1); IR (CHCl3 cast) 3107, 2960, 2194, 2101,
1
1505, 1250 cm-1; H NMR (500 MHz, CDCl3) δ 8.31 (d, J )
8.1 Hz, 1H), 7.86 (d, J ) 7.8 Hz, 1H), 7.83 (d, J ) 8.1 Hz, 1H),
7.73 (dd, J ) 7.2, 1.1 Hz, 1H), 7.57 (ddd, J ) 8.3, 6.8, 1.4 Hz,
1H), 7.51 (ddd, J ) 8.1, 6.8, 1.4 Hz, 1H), 7.40 (dd, J ) 8.3, 7.2
Hz, 1H), 0.27 (s, 9H); 13C NMR (125 MHz, APT, CDCl3) δ 134.0,
133.0, 132.2, 129.7, 128.3, 127.1, 126.6, 126.0, 125.1, 119.0,
91.7, 88.0, 78.8, 75.1, -0.2; EI HRMS m/z calcd for C17H16Si
(M+) 248.1021, found 248.1019.
[4-(1-P yr en yl)-1,3-bu ta d iyn yl]tr im eth ylsila n e (8b). Di-
bromoolefin 7b (177 mg, 0.367 mmol) was reacted in hexanes
(20 mL) at -50 °C (rather than -78 °C due to decreased
solubility of dibromoolefin 7b) with n-BuLi (0.16 mL, 2.5 M
in hexanes, 0.40 mmol) to give 8b (92.8 mg, 79%) as a bright
yellow solid: mp 124-125 °C; Rf ) 0.8 (CH2Cl2/hexanes, 1:1);
1
1251 cm-1; H NMR (300 MHz, CD2Cl2) δ 7.31 (m, 2H), 7.10
1
IR (CHCl3 cast) 3046, 2195, 2095, 1250 cm-1; H NMR (300
(m, 1H), 0.17 (s, 9H); 13C NMR (75 MHz, APT, CD2Cl2) δ 134.7,
128.9, 127.2, 121.7, 93.0, 87.6, 78.3, 69.8, -0.4; MS (EI, 70
eV) m/z 204.0 (M+, 37), 189.0 ([M - CH3]+, 100); EI HRMS
m/z calcd for C11H12SSi (M+) 204.0429, found 204.0424.
(4-F er r ocen yl-1,3-bu ta d iyn yl)tr im eth ylsila n e (8k ). To
dibromoolefin 7k (153 mg, 0.373 mmol) in dry hexanes (10 mL)
at -78 °C was added dropwise over 10 min 1 equiv of n-BuLi
(0.16 mL, 2.5 M in hexanes, 0.40 mmol). The mixture was
MHz, CDCl3) δ 8.47 (d, J ) 9.0 Hz, 1H), 8.10 (m, 4H), 7.98 (m,
3H), 7.92 (t, J ) 9.0 Hz, 1H), 0.35 (s, 9H); 13C NMR (75 MHz,
CDCl3) δ 133.5, 131.8, 131.0, 130.8, 130.6, 128.8, 128.7, 127.0,
126.3, 125.9, 125.8, 125.1, 124.3, 124.1, 123.9, 115.4, 92.2, 88.4,
79.6, 76.3, -0.2; EI HRMS m/z calcd for
322.1178, found 322.1174.
C
23H18Si (M+)
(36) The general experimental details and characterization for all
alcohols, ketones, and dibromoolefin precursors are detailed in the
Supporting Information.
(37) Wan, W. B.; Haley, M. M. J . Org. Chem. 2001, 66, 3893-3901.
J . Org. Chem, Vol. 68, No. 4, 2003 1345

Shi Shun et al.
warmed to -20 °C and cooled to -78 °C, and an additional
1/4 equiv of n-BuLi (0.04 mL, 2.5 M in hexanes) was added.
Workup as per the general procedure and purification via
column chromatography (hexanes/CH2Cl2, 2:1) gave diyne 8k
(32 mg, 28%) as an orange oil: Rf ) 0.7 (hexanes/CH2Cl2, 1:1);
with n-BuLi (0.16 mL, 2.5 M in hexanes, 0.40 mmol) as per
the general procedure to give diyne 11a (76.1 mg, 70%) as a
colorless oil: Rf ) 0.6 (hexanes); IR (CHCl3 cast) 3029, 2958,
1
2204, 2103, 1251 cm-1; H NMR (400 MHz, CDCl3) δ 7.38 (d,
J ) 8.3 Hz, 2H), 7.10 (d, J ) 8.3 Hz, 2H), 2.57 (t, J ) 7.7 Hz,
IR (CH2Cl2 cast) 2925, 2205, 2102, 1249 cm-1; H NMR (300
2H), 1.57 (m, 2H), 1.27 (m, 6H), 0.86 (m, 3H), 0.21 (s, 9H); 13
C
1
MHz, CDCl3) δ 4.49 (t, J ) 1.8 Hz, 2H), 4.25 (s, 5H), 4.24 (t,
J ) 1.8 Hz, 2H), 0.23 (s, 9H); 13C NMR (75 MHz, APT, CDCl3)
δ 88.7, 87.6, 77.3, 72.3, 70.5, 70.2, 69.4, 62.5, -0.3; EI HRMS
m/z calcd for C17H18SiFe (M+) 306.0527, found 306.0530.
NMR (125 MHz, CDCl3) δ 144.7, 132.6, 128.5, 118.4, 90.1, 88.0,
77.1, 73.5, 36.0, 31.6, 31.1, 28.9, 22.5, 14.0, -0.4; MS (EI, 70
eV) m/z 282.2 (M+, 65), 267.2 ([M - CH3]+, 100); EI HRMS
m/z calcd for C19H26Si (M+) 282.1804, found 282.1796. Anal.
Calcd for C19H26Si: C, 80.78; H, 9.28. Found: C, 80.73; H, 9.54.
[4-(4-t er t -Bu t ylp h e n yl)-1,3-b u t a d iyn yl]t r im e t h ylsi-
la n e (11b). Dibromoolefin 10b (152 mg, 0.367 mmol) was
reacted with n-BuLi (0.15 mL, 2.5 M in hexanes, 0.38 mmol)
as per the general procedure to give diyne 11b (82.2 mg, 88%)
as a yellow crystalline solid. Spectral data were consistent with
those reported by Haley.37
(6-P h en ylh ex-5-en e-1,3-d iyn yl)tr im eth ylsila n e (8l). Di-
bromoolefin 7l (610 mg, 1.59 mmol) was reacted with n-BuLi
(0.76 mL, 2.5 M in hexanes, 1.9 mmol) as per the general
procedure to give diyne 8l (338 mg, 95%) as a yellow oil: Rf )
0.4 (hexanes); IR (CHCl3 cast) 3030, 2959, 2925, 2191, 2092,
1605, 1492, 1448 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.34 (m,
5H), 7.08 (d, J ) 16.2 Hz, 1H), 6.16 (d, J ) 16.2 Hz, 1H), 0.22
(s, 9H); 13C NMR (100 MHz, APT, CDCl3) δ 145.1, 135.6, 129.3,
128.8, 126.4, 106.3, 91.3, 88.0, 76.5, 76.3, -0.4; MS (EI, 70
eV) m/z 224.1 (M+, 50), 209.1 ([M - CH3]+, 100); EI HRMS
m/z calcd for C15H16Si (M+) 224.1021, found 224.1020. Anal.
Calcd for C15H16Si: C, 80.29; H, 7.19. Found: C, 80.06; H, 7.16.
[4-(4-Tr im eth ylsilyl-1,3-bu ta d iyn yl)p h en yl]p h en yld ia -
zen e (11c). Dibromoolefin 10c (170 mg, 0.369 mmol) was
reacted with n-BuLi (0.15 mL, 2.5 M in hexanes, 0.38 mmol)
as per the general procedure to give diyne 11c (67.6 mg, 61%)
as a red solid: mp 103-104 °C; Rf ) 0.7 (hexanes/CH2Cl2, 2:1);
IR (CH2Cl2 cast) 2960, 2202, 2102, 1404, 1278, 1253, 842 cm-1
;
[4-(S)-(-)-P er illyl-1,3-bu ta d ien yl]tr im eth ylsila n e (8m ).
Dibromoolefin 7m (131 mg, 0.324 mmol) was reacted with
n-BuLi (0.16 mL, 2.5 M in hexanes, 0.40 mmol) as per the
general procedure to give diyne 8m (37 mg, 46%) as a pale
yellow oil which solidified into a yellow solid upon refrigera-
tion: mp 52-54 °C; Rf ) 0.3 (hexanes); IR (CH2Cl2 cast) 3082,
1H NMR (400 MHz, CDCl3) δ 7.91 (dd, J ) 8.3, 1.8 Hz, 2H),
7.86 (d, J ) 8.7 Hz, 2H), 7.62 (d, J ) 8.7 Hz, 2H), 7.50 (m,
3H), 0.24 (s, 9H); 13C NMR (100 MHz, CDCl3) 152.5, 152.3,
133.5, 131.4, 129.1, 123.9, 123.0, 122.9, 92.2, 87.7, 76.4, 76.4,
-0.2; MS (EI, 70 eV) m/z 302.1 (M+, 89), 297.0 ([M - C6H3N2]+,
100); EI HRMS m/z calcd for C19H18N2Si (M+) 302.1239, found
302.1245. Anal. Calcd for C19H18N2Si: C, 75.45; H, 6.00; N,
9.26. Found: C, 74.92; H, 5.92; N, 9.18.
2960, 2198, 2098, 1676, 1645 cm-1; [R]22 -17.2° (c ) 0.0029,
D
1
CH2Cl2); H NMR (400 MHz, CDCl3) δ 6.29 (m, 1H), 4.73 (m,
1H), 4.69 (m, 1H), 2.20 (m, 3H), 2.10 (m, 1H), 2.03 (m, 1H),
1.80 (m, 1H), 1.71 (s, 3H), 1.45 (m, 1H), 0.18 (s, 9H); 13C NMR
(100 MHz, APT, CDCl3) δ 148.8, 138.7, 119.1, 109.2, 89.4, 88.1,
78.5, 72.0, 39.8, 31.3, 28.9, 27.0, 20.6, -0.4; MS (EI, 70 eV)
m/z 242.1 (M+, 51); EI HRMS m/z calcd for C16H22Si (M+)
242.1491, found 242.1491.
1-(3-Meth oxyp h en yl)-1,3-octa d iyn e (8p ). Dibromoolefin
7p (121 mg, 0.325 mmol) was reacted with n-BuLi (0.23 mL,
1.6 M in hexanes, 0.37 mmol) as per the general procedure to
give diyne 8p (63.3 mg, 92%) as a yellow oil: Rf ) 0.6 (hexanes/
CH2Cl2, 2:1); IR (CH2Cl2 cast) 3072, 3002, 2958, 2242, 2152,
1601, 1594, 1574, 1489, 1427 cm-1; 1H NMR (400 MHz, CDCl3)
δ 7.19 (t, J ) 8.0 Hz, 1H), 7.05 (dd, J ) 1.0, 1.5 Hz, 1H), 6.98
(dd, J ) 2.6, 1.5 Hz, 1H), 6.87 (ddd, J ) 8.0, 2.6, 1.0 Hz, 1H),
3.77 (s, 3H), 2.35 (t, J ) 7.0 Hz, 2H), 1.55 (m, 2H), 1.45 (m,
2H), 0.92 (t, J ) 7.3 Hz, 3H); 13C NMR (100 MHz, APT, CDCl3)
δ 159.2, 129.5, 125.1, 123.1, 117.2, 115.7, 84.9, 74.6, 74.2, 65.0,
[4-(3,4,5-Tr im eth oxyp h en yl)-1,3-bu ta d iyn yl]tr im eth yl-
sila n e (11d ). Dibromoolefin 10d (255 mg, 0.569 mmol) was
reacted with n-BuLi (0.27 mL, 2.5 M in hexanes, 0.68 mmol)
as per the general procedure, and purification by column
chromatography (SiO2, hexanes/CH2Cl2, 4:1) gave diyne 11d
(83.1 mg, 51%) as a yellow solid: mp 75-78 °C; Rf ) 0.2
(hexanes/CH2Cl2, 1:1); IR (CHCl3 cast) 2959, 2203, 2095, 1249,
1130 cm-1; 1H NMR (400 MHz, CDCl3) δ 6.71 (s, 2H), 3.84 (s,
3H), 3.82 (s, 6H), 0.21 (s, 9H); 13C NMR (100 MHz, APT, CDCl3)
δ 153.0, 140.0, 116.1, 109.9, 90.6, 87.7, 76.8, 73.3, 60.9, 56.1,
-0.4; EI HRMS m/z calcd for C16H20O3Si (M+) 288.1182, found
288.1179. Anal. Calcd for C16H20O3Si: C, 66.63; H, 6.99.
Found: C, 66.73; H, 7.03.
[6-(2-Th ien yl)h ex-5-en e-1,3-diyn yl]tr im eth ylsilan e (11e).
Dibromoolefin 10e (679 mg, 1.74 mmol) was reacted with
n-BuLi (0.84 mL, 2.5 M in hexanes, 2.1 mmol) as per the
general procedure to give diyne 11e (221 mg, 55%) as a yellow
oil: Rf ) 0.3 (hexanes); IR (CH2Cl2 cast) 2959, 2188, 2093,
55.3, 30.3, 21.9, 19.3, 13.5; EI HRMS m/z calcd for C15H16
O
(M+) 212.1201, found 212.1200.
1
1593, 1425, 1250 cm-1; H NMR (400 MHz, CDCl3) δ 7.23 (d,
1-(2-Th ien yl)-1,3-octa d iyn e (8q). Dibromoolefin 7q (70.9
mg, 0.204 mmol) was reacted with n-BuLi (0.15 mL, 1.6 M in
hexanes, 0.24 mmol) as per the general procedure to give diyne
8q (32.9 mg, 86%) as a yellow oil: Rf ) 0.7 (hexanes); IR (CH2-
J ) 5.1 Hz, 1H), 7.16 (d, J ) 15.9 Hz, 1H), 7.05 (d, J ) 3.6 Hz,
1H), 6.99 (dd, J ) 5.1, 3.6 Hz, 1H), 5.95 (d, J ) 15.9 Hz, 1H),
0.21 (s, 9H); 13C NMR (100 MHz, APT, CDCl3) δ 140.8, 137.7,
128.0, 127.9, 126.4, 105.3, 91.6, 88.0, 76.7, 76.3, -0.4; MS (EI,
70 eV) m/z 230.1 (M+, 55), 215.0 ([M - CH3]+, 100); HRMS
m/z calcd for C13H14SSi (M+) 230.0586, found 230.0586. Anal.
Calcd for C13H14SSi: C, 67.77; H, 6.13. Found: C, 67.50; H,
6.27.
Cl2 cast) 3106, 2957, 2931, 2871, 2231, 2151, 1465, 1425 cm-1
;
1H NMR (400 MHz, CDCl3) δ 7.25 (dd, J ) 3.7, 1.1 Hz, 1H),
7.23 (dd, J ) 5.1, 1.1 Hz, 1H), 6.94 (dd, J ) 5.1, 3.7 Hz, 1H),
2.36 (t, J ) 7.0 Hz, 2H), 1.54 (m, 2H), 1.44 (m, 2H), 0.92 (t, J
) 7.3 Hz, 3H); 13C NMR (100 MHz, APT, CDCl3) δ 133.8, 127.9,
127.0, 122.5, 87.0, 78.5, 67.6, 64.9, 30.2, 21.9, 19.4, 13.5; EI
HRMS m/z calcd for C12H12S (M+) 188.0660, found 188.0662.
[6-(4-n -H e xylp h e n yl)-1,3,5-h e xa t r iyn yl]t r im e t h ylsi-
la n e (14a ). Dibromoolefin 13a (171 mg, 0.366 mmol) was
reacted with n-BuLi (0.15 mL, 2.5 M in hexanes, 0.38 mmol)
as per the general procedure to give triyne 14a (46.4 mg, 41%)
as a light yellow oil: Rf ) 0.7 (hexanes); IR (CH2Cl2 cast) 3029,
2957, 2928, 2856, 2176, 2075, 1604, 1509, 1251 cm-1; 1H NMR
(400 MHz, CDCl3) δ 7.41 (d, J ) 8.2 Hz, 2H), 7.12 (d, J ) 8.2
Hz, 2H), 2.59 (t, J ) 7.8 Hz, 2H), 1.60 (m, 2H), 1.28 (m, 6H),
0.87 (m, 3H), 0.21 (s, 9H); 13C NMR (75 MHz, APT, CDCl3) δ
145.4, 133.1, 128.7, 117.9, 88.8, 88.2, 77.4, 73.8, 66.6, 61.9, 36.1,
31.7, 31.1, 28.9, 22.6, 14.1, -0.4; MS (EI, 70 eV) m/z 306.2
(M+, 96), 291.2 ([M - CH3]+, 100); EI HRMS m/z calcd for
1-(2-Th ien yl)-1,3-p en ta d iyn e (8r ). Dibromoolefin 7r (76.6
mg, 0.250 mmol) was reacted with n-BuLi (0.12 mL, 2.5 M in
hexanes, 0.30 mmol) as per the general procedure to give diyne
8r (14.8 mg, 41%) as a colorless oil: Rf ) 0.5 (hexanes); IR
(CHCl3 cast) 3105, 2912, 2850, 2236, 2150, 1426 cm-1; 1H NMR
(400 MHz, CDCl3) δ 7.26 (dd, J ) 3.7, 1.2 Hz, 1H), 7.25 (dd, J
) 5.2, 1.2 Hz, 1H), 6.94 (dd, J ) 5.2, 3.7 Hz, 1H), 2.01 (s, 3H);
13C NMR (125 MHz, APT, CDCl3) δ 133.9, 128.0, 127.0, 122.4,
82.6, 78.6, 67.2, 64.3, 4.8; EI HRMS m/z calcd for C9H6S (M+)
146.0190, found 146.0188.
[4-(4-n -H exylp h en yl)-1,3-b u t a d iyn yl]t r im et h ylsila n e
(11a ). Dibromoolefin 10a (170 mg, 0.384 mmol) was reacted
C
C
21H26Si (M+) 306.1804, found 306.1817. Anal. Calcd for
21H26Si: C, 82.29; H, 8.55. Found: C, 81.82; H, 8.74.
1346 J . Org. Chem., Vol. 68, No. 4, 2003

Synthesis of 1,3-Butadiynes and 1,3,5-Hexatriynes
[6-(4-ter t-Bu tylp h en yl)-1,3,5-h exa tr iyn yl]tr im eth ylsi-
la n e (14b). Dibromoolefin 13b (80.6 mg, 0.184 mmol) was
reacted with n-BuLi (0.08 mL, 2.5 M in hexanes, 0.20 mmol)
as per the general procedure to give triyne 14b (50.0 mg, 98%)
as a yellow solid: mp 78-80 °C; Rf ) 0.9 (hexanes/CH2Cl2,
2:1); IR (CHCl3 cast) 2962, 2903, 2181, 2169, 2075, 1652, 1599,
CDCl3) δ 147.4, 135.9, 130.9, 106.3, 89.2, 88.3, 77.2, 76.0, 67.3,
62.0, 18.6, -0.4; MS (EI, 70 eV) m/z 212.1 (M+, 96), 197.1 ([M
- CH3]+, 100); EI HRMS m/z calcd for C14H16Si (M+) 212.1021,
found 212.1019.
1,4-Bis(4-t r im et h ylsilyl-1,3-b u t a d iyn yl)b en zen e (18).
Dibromoolefin 17 (4.12 g, 6.46 mmol) was reacted with n-BuLi
(6.2 mL, 2.5 M in hexanes, 15.5 mmol) as per the general
procedure to give tetrayne 18 (1.79 g, 87%) as colorless
crystals: mp 187-188 °C; Rf ) 0.4 (hexanes); IR (CHCl3 cast)
1
1504, 1462, 1407 cm-1; H NMR (400 MHz, CDCl3) δ 7.44 (d,
J ) 8.7 Hz, 2H), 7.33 (d, J ) 8.7 Hz, 2H), 1.30 (s, 9H), 0.21 (s,
9H); 13C NMR (75 MHz, APT, CDCl3) δ 153.5, 132.9, 125.6,
117.7, 88.8, 88.2, 77.3, 73.8, 66.6, 61.9, 35.0, 31.1, -0.4; MS
(EI, 70 eV) m/z 278.1 (M+, 49), 263.1 ([M - CH3]+, 100); EI
HRMS m/z calcd for C19H22Si (M+) 278.1491, found 278.1497.
[4-(6-Tr im eth ylsilyl-1,3,5-h exa tr iyn yl)p h en yl]p h en yl-
d ia zen e (14c). Dibromoolefin 13c (54.7 mg, 0.113 mmol) was
reacted with n-BuLi (0.04 mL, 2.5 M in hexanes, 0.10 mmol)
as per the general procedure to give triyne 14c (16.8 mg, 46%)
as a bright orange solid, a mixture of E- and Z-isomers: mp
88-89 °C; Rf ) 0.6 (hexanes/CH2Cl2, 4:1); IR (CH2Cl2 cast)
2959, 2167, 2075, 1248, 843 cm-1; 1H NMR (400 MHz, CDCl3)
δ 7.91 (dd, J ) 8.3, 2.1 Hz, 2H), 7.87 (d, J ) 8.8 Hz, 2H), 7.65
(d, J ) 8.8 Hz, 2H), 7.50 (m, 3H), 0.23 (s, 9H); 13C NMR (75
MHz, APT, CDCl3) δ (major isomer) 152.7, 152.6, 134.0, 131.6,
129.2, 123.3, 123.1, 123.0, 89.9, 88.0, 77.3, 76.5, 68.1, 61.4,
-0.5; MS (EI, 70 eV) m/z 326.1 (M+, 93), 221.1 ([M - C6H5N2]+,
100); EI HRMS m/z calcd for C21H18N2Si (M+) 326.1239, found
326.1241.
(8-P h en yloct-7-en e-1,3,5-tr iyn yl)tr im eth ylsila n e (14d ).
Dibromoolefin 13d (420 mg, 1.03 mmol) was reacted with
n-BuLi (0.49 mL, 2.5 M in hexanes, 1.2 mmol) as per the
general procedure to give diyne 14d (210 mg, 82%) as an
orange/yellow oil: Rf ) 0.3 (hexanes); IR (CHCl3 cast) 3030,
2959, 2162, 2073, 1601, 1448 cm-1; 1H NMR (400 MHz, CDCl3)
δ 7.36 (m, 5H), 7.15 (d, J ) 16.3 Hz, 1H), 6.18 (d, J ) 16.3 Hz,
1H), 0.24 (s, 9H); 13C NMR (100 MHz, APT, CDCl3) δ 146.5,
135.4, 129.6, 128.8, 126.6, 105.8, 89.4, 88.2, 76.8, 76.5, 67.5,
61.9, -0.5; MS (EI, 70 eV) m/z 248.1 (M+, 59), 233.1 ([M -
CH3]+, 100); EI HRMS m/z calcd for C17H16Si (M+) 248.1021,
found 248.1018. Anal. Calcd for C17H16Si: C, 82.20; H, 6.49.
Found: C, 82.19; H, 6.78.
2957, 2209, 2105, 1400 cm-1 1H NMR (400 MHz, CDCl3) δ
;
7.40 (s, 4H), 0.21 (s, 18H); 13C NMR (100 MHz, CDCl3) δ 132.6,
122.3, 92.4, 87.5, 76.7, 75.9, -0.5; MS (EI, 70 eV) m/z 318.1
(M+, 75), 303.1 ([M - CH3]+, 100); EI HRMS m/z calcd for
C
C
20H22Si2 (M+) 318.1260, found 318.1261. Anal. Calcd for
20H22Si2: C, 75.40; H, 6.96. Found: C, 75.01; H, 6.89.
1,4-Bis[4-(2-th ien yl)-1,3-bu ta d iyn yl]ben zen e (21). The
bis(dibromoolefin) 19 (37.6 mg, 0.057 mmol) was stirred in 7
mL of dry hexanes at -78 °C, and n-BuLi (0.24 mL, 2.5 M in
hexanes, 1.4 mmol) was added. The heterogeneous mixture
was then warmed to about -10 °C for several minutes and
then cooled to -78 °C before workup. Addition of CH2Cl2was
required to solubilize the product for workup. Recrystallization
(hexanes/CH2Cl2) yielded 21 (4.5 mg, 24%) as a shiny light-
brown solid: mp 261 °C dec; Rf ) 0.7 (hexanes/CH2Cl2, 1:1);
IR (microscope) 3101, 2202, 2143, 1663 cm-1 1H NMR (400
;
MHz, CD2Cl2) δ 7.48 (s 4H), 7.37 (d, J ) 4.4 Hz, 4H), 7.01 (m,
2H); 13C NMR (100 MHz, APT, CD2Cl2) δ 135.2, 132.8, 129.7,
127.7, 122.9, 121.9, 83.2, 77.8, 76.4, 76.3; EI HRMS m/z calcd
for C22H10S2 (M+) 338.0224, found 338.0220.
1,4-Bis[4-(4-ter t-b u t ylp h en yl)-1,3-b u t a d iyn yl]-2,5-b is-
(octyloxy)ben zen e (22). Dibromoolefin 20 (16 mg, 0.016
mmol) was reacted with n-BuLi (0.01 mL, 2.5 M in hexanes,
0.031 mmol) as per the general procedure to give tetrayne 22
(10.7 mg, 98%) as a yellow waxy solid: mp 118-119 °C; Rf )
0.8 (hexanes/EtOAc, 9:1); IR (CH2Cl2 cast) 2924, 2209, 2143,
1603, 1467, 1262, 1221 cm-1 1H NMR (400 MHz, CDCl3) δ
;
7.44 (d, J ) 8.6 Hz, 4H), 7.34 (d, J ) 8.6 Hz, 4H), 6.94 (s, 2H),
3.96 (t, J ) 6.6 Hz, 4H), 1.80 (quint, J ) 6.8 Hz, 4H), 1.47 (m,
4H), 1.30 (s, 18H), 1.27 (m, 16H), 0.85 (m, 6H); 13C NMR (100
MHz, CDCl3) δ 154.8, 152.7, 132.3, 125.5, 118.8, 117.7, 113.6,
83.5, 79.7, 77.6, 73.6, 69.8, 34.9, 31.8, 31.1, 29.3, 29.26, 29.1,
[8-(2-Th ien yl)oct -7-en e-1,3,5-t r iyn yl]t r im et h ylsila n e
(14e). Dibromoolefin 13e (459 mg, 1.11 mmol) was reacted
with n-BuLi (0.53 mL, 2.5 M in hexanes, 1.3 mmol) as per the
general procedure to give triyne 14e (209 mg, 74%) as a yellow
solid: mp 55-56 °C; Rf ) 0.3 (hexanes); IR (CH2Cl2 cast) 2959,
26.0, 22.7, 14.1; EI HRMS m/z calcd for
C
50H62O2 (M+)
694.4750, found 694.4742.
2898, 2161, 2083, 2061, 1589, 1425, 1311, 1288, 1250 cm-1
;
Ack n ow led gm en t. We gratefully acknowledge the
University of Alberta, the Natural Sciences and Engi-
neering Research Council of Canada (NSERC), and
PetroCanada (Young Innovator Award to R.R.T.) for
financial support, NSERC for a summer undergraduate
research scholarship provided to E.T.C., and Dr. Michael
Ferguson for the crystal structure determination of
compound 18.
1H NMR (400 MHz, CDCl3) δ 7.25 (d, J ) 5.7 Hz, 1H), 7.23 (d,
J ) 15.6 Hz, 1H), 7.07 (d, J ) 3.6 Hz, 1H), 7.00 (dd, J ) 5.7,
3.6 Hz, 1H), 5.95 (d, J ) 15.9 Hz, 1H), 0.20 (s, 9H); 13C NMR
(100 MHz, APT, CDCl3) δ 140.6, 139.0, 128.5, 128.0, 126.9,
104.7, 89.6, 88.1, 76.9, 76.5, 67.8, 61.8, -0.5; MS (EI, 70 eV)
m/z 254.1 (M+, 80), 239.0 ([M - CH3]+, 100); EI HRMS m/z
calcd for C15H14SSi (M+) 254.0586, found 254.0590.
(Un d eca -7,9-d ien e-1,3,5-tr iyn yl)tr im eth ylsila n e (14f).
Dibromoolefin 13f (104 mg, 0.279 mmol) was reacted with
n-BuLi (0.13 mL, 2.5 M in hexanes, 0.34 mmol) as per the
general procedure to give diyne 14f (45.0 mg, 76%) as a pale
yellow solid: mp 48-49 °C; Rf ) 0.5 (hexanes); IR (CHCl3 cast)
2958, 2924, 2853, 2162, 2074 cm-1; 1H NMR (300 MHz, CDCl3)
δ 6.74 (dd, J ) 15.6, 10.8 Hz, 1H), 6.11 (dd, J ) 14.7, 10.8 Hz,
1H), 5.90 (dq, J ) 14.7, 6.3 Hz, 1H), 5.46 (d, J ) 15.6 Hz, 1H),
1.79 (d, J ) 6.3 Hz, 3H), 0.18 (s, 9H); 13C NMR (75 MHz, APT,
Su p p or tin g In for m a tion Ava ila ble: General experimen-
tal and spectroscopic details for precursor alcohols, ketones,
and dibromoolefins, 1H and 13C NMR spectra for all unpub-
lished products, and X-ray crystallographic data for compound
18. This material is available free of charge via the Internet
at http://pubs.acs.org.
J O026481H
J . Org. Chem, Vol. 68, No. 4, 2003 1347