ORGANIC
LETTERS
2005
Vol. 7, No. 2
343-345
Palladium-Catalyzed Inter- and
Intramolecular Coupling Reactions of
Aryl and Vinyl Halides Mediated by
Indium
Phil Ho Lee,* Dong Seomoon, and Kooyeon Lee
Department of Chemistry, Kangwon National UniVersity,
Chunchon 200-701, Republic of Korea
Received November 26, 2004
ABSTRACT
Treatment of aryl and vinyl halides with 50 mol % of 100 mesh indium, 2.5 mol % of Pd
−C, and 1.5 equiv of LiCl under mild conditions (DMF,
100 C, 1 3 h) could produce coupling products efficiently in good to excellent yields in which the Csp2−
°
−
Csp2 bond was formed. This reagent
worked equally well with both intermolecular and intramolecular coupling reactions, producing a variety of biaryls, 1,3-dienes, and cyclic
compounds.
The Csp2-Csp2 bond formation is one of the most useful
reactions in organic synthesis.1 Traditionally, copper-
catalyzed coupling reactions of aryl and vinyl halides have
been extensively used for the formation of biaryls and 1,3-
dienes.2 However, the use of high temperatures (neat, >200
°C), poor substrate scope, and the need to use stoichiometric
amounts of copper reagents have limited the utility of these
reactions in some cases.2 Ullmann reductive coupling reac-
tions of aryl, heteroaryl, and alkenyl halides proceeded with
copper(I) thiophene-2-carboxylate and substrates possessing
a coordinating ortho substituent at room temperature.3
Although nickel in the presence of reducing agents such as
zinc, LiH, and NaH has been applied in the Ullmann reaction,
excess use of reducing agents and additives makes functional
group tolerance narrow.4 Pd-mediated coupling reactions of
aryl and vinyl halides reported to date require inconvenient
reaction conditions to regenerate Pd(0) species, high tem-
perature, several specific ligands, and additives.5 Thus, over-
coming the harsh conditions typically required for Ullmann
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W., Eds.; Pergamon: Oxford, 1982; Vol. 8, pp 799-938. (c) Farina, V. In
ComprehensiVe Organometallic Chemistry II; Wilkinson, G., Stone, F. G.,
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Tsuji, J. Palladium Reagents and Catalyst; Wiley: Chichester, U.K., 1995;
Chapter 4. (e) Diederich, F., Stang, P. J., Eds. Metal-Catalyzed Cross-
couplings Reactions; Wiley-VCH: Weinheim, 1998. (f) Malleron, J.; Fiaud,
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1974, 9. (c) Cohon, T.; Cristea, I. J. Org. Chem. 1975, 40, 3649. (d)
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J. G.; Stauffer, R. D. J. Am. Chem. Soc. 1981, 103, 6460. (d) Chao, C. S.;
Cheng, C. H.; Chang, C. T. J. Org. Chem. 1983, 48, 4904. (e) Takagi, K.;
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10.1021/ol047567v CCC: $30.25
© 2005 American Chemical Society
Published on Web 12/23/2004