Palladium-catalyzed three-component coupling reactions of 2-(cyanomethyl)phenol, aryl halides, and carbon monoxide

Three-component coupling reactions of 2-(cyanomethyl)phenol, aryl halides, and carbon monoxide (CO) in orthogonal-tandem catalysis were investigated. In the reactions, 2-(cyanomethyl)phenyl esters, which are produced through Pd(PPh3)(4)-catalyzed alkoxycarbonylation of aryl halides with 2-(cyano-methyl)phenol, undergo cycloisomerization in situ catalyzed by Pd(PCy3)(2) as a co-catalyst to give 3-acyl-2-aminobenzofurans. Palladium species with homoleptic tertiary phosphines, such as Pd(PPh3)(4) and Pd(PCy3)(2), can catalyze the mechanistically distinct reactions in an orthogonal tandem manner without interference. By switching the base used in this reaction, 3-acyl-2-(N-acylamino)benzofurans were obtained as major products instead of 3-acyl-2-aminobenzofurans. Given that 2-(cyanomethyl)phenols can be synthesized from commercially available salicylic acid derivatives in two steps, the present method thus provides facile access to synthetically useful 3-acyl-2-aminobenzofurans. (C) 2015 Elsevier Ltd. All rights reserved.