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Benzofurans, Indoles, and Isoquinolones via Castro-Stephens and Heck Reactions
R. Álvarez*, C. Martínez, Y. Madich, J. G. Denis, J. M. Aurrecoechea*, Á. R. de Lera*
Universidade de Vigo and Universidad del País Vasco, Bilbao, Spain
21 December 2010 (online)
Reported is the synthesis of benzofurans A, indoles B, and isoquinolones C via a Sonogashira coupling and subsequent sequential Castro-Stephens and Heck strategy. In the case of the benzofuran synthesis, a detailed screen of catalyst, additives, base, temperature, and equivalents of alkene is described, which led to the optimum conditions as shown above. Substrate scope is examined, particularly the effects of varying the alkyne (R¹) and amide (R5) substituents, which shows good tolerance to modification.