applications of this carboxylation reaction and the develop-
ment of a catalytic process are now in progress.
Table 3. Carboxylation of 1d with Functionalized Organozinc
Reagents
Acknowledgment. This work was supported by a Grant-
in-Aid for Scientific Research (Grant No. 12771345) from
the Japan Society for the Promotion of Science (JSPS).
Supporting Information Available: Information on
experimental procedures, spectral data for substrate 1d, and
spectral data for compounds 3a-d, 8-12, and 17-20. This
material is available free of charge via the Internet at
OL016585Z
(3) Recent reports of catalytic reactions involving a related coupling
process: (a) Inoue, Y.; Itoh, Y.; Kazama, H.; Hashimoto, H. Bull. Chem.
Soc. Jpn. 1980, 53, 3329. (b) Tsuda, T.; Morikawa, S.; Hasegawa, N.;
Saegusa, T. J. Org. Chem. 1990, 55, 2978. (d) De`rien, S.; Clinet, J.-C.;
Dun˜ach, E.; Pe`richon, J. J. Am. Chem. Soc. 1991, 113, 8447.
(4) Dun˜ach also reported a nickel-catalyzed electrochemical carboxylation
of terminal alkynes which afforded R-substituted-R,â-unsaturated acid in a
reverse regioselectivity. (a) Dun˜ach, E.; Pe`richon, J. J. Organomet. Chem.
1988, 352, 239. (b) Dun˜ach, E.; Pe`richon, J. J. Organomet. Chem. 1990,
385, C43. See also ref 3d.
(5) Transmetalation processes of structurally related oxanickelacycles
with organozinc reagents were already reported by Montgomery. (a)
Oblinger, E.; Montgomery, J. J. Am. Chem. Soc. 1997, 119, 9065. (b)
Montgomery, J. Acc. Chem. Res. 2000, 33, 467.
a Isolated yield based on Ni(cod)2.
(6) We recently reported a cross-coupling reaction of nickel complexes
generated from 1,3-diene and CO2 with organozinc reagents which was
based on a similar concept. Takimoto, M.; Mori, M. J. Am. Chem. Soc.
2001, 123, 2895.
(7) The actual yield based on used Ni(cod)2 was 110%, which exceeded
the amount of the limiting reagent. This result suggested that zero-valent
nickel species regenerated and that the reaction could proceed by a catalytic
amount of nickel complex. However, our initial attempt at a catalytic
experiment using 25 mol % of Ni(cod)2 was unsuccessful and 3a was
obtained in only 30% yield.
intermediate X. Reductive elimination of Ni(0) from X would
afford XI, which would be hydrolyzed to give 12. It was
very interesting that the use of butylzinc iodide 7 instead of
6 afforded the desired â-alkylated product 11 in good yield,
although the alkyl group of 7 possesses â-hydrogen atoms.
As documented in Table 3, various organozinc reagents
having an ester group as a functional group were also
applicable to this reaction.10 High yields were generally
obtained except for the case of Reformatsky reagent 14.14
Reactions using linear alkylzinc reagents 15 and 16 afforded
the desired products 19 and 20, respectively, in high yields
without the occurrence of â-hydride elimination.
In summary, we succeeded in the alkylative or arylative
carboxylation of terminal alkynes. The remarkable feature
of this reaction is that the reaction proceeds under very mild
conditions in a highly regio- and stereoselective manner. Not
only aromatic but also aliphatic terminal alkynes gave â,â′-
disubstituted unsaturated carboxylic acid in high yields.
Various organozinc reagents, including functionalized aryl-
or alkylzinc reagents, could be used. Further studies on
(8) For the preparation of benzylzinc bromide, see: Berk, S. C.; Knochel,
P.; Yeh, M. C. P. J. Org. Chem. 1988, 53, 5789.
(9) Butylzinc iodide was prepared from butyl iodide and metallic zinc
according to a method described in the following report. Knochel, P.; Yeh,
M. C. P.; Berk, S. C.; Talbert, J. J. Org. Chem. 1988, 53, 2390.
(10) Reviews for functionalized zinc reagents: (a) Knochel, P.; Singer,
R. D. Chem. ReV. 1993, 93, 2117. (b) Rieke, R. D. Aldrichimica Acta 2000,
33, 52. For the preparation of specific zinc reagents that appear in Table 3,
see refs 11-13.
(11) Arylzinc iodide 13: Zhu, L.; Wehmeyer, R. M.; Rieke, R. D. J.
Org. Chem. 1991, 56, 1445.
(12) Reformatsky reagent 14: (a) Cure´, J.; Gaudemar, M. Bull. Soc.
Chim. Fr. 1968, 8, 3224. (b) Cure´, J.; Gaudemar, M. Bull. Soc. Chim. Fr.
1969, 9, 2471.
(13) For the preparation of organozinc reagents 15 and 16, see ref 9.
(14) It is not clear yet why the yield of the reaction using 14 was low.
We have tentatively speculated that 14 was lost by the reaction with CO2,
since the nucleophilicity of 14 is higher than that of other organozinc
reagents.
Org. Lett., Vol. 3, No. 21, 2001
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