Palladium-catalyzed Tsuji–Trost-type reaction of benzofuran-2-ylmethyl acetates with nucleophiles

Abstract

The palladium-catalyzed benzylic-like nucleophilic substitution of benzofuran-2-ylmethyl acetate with N, S, O and C soft nucleophiles has been investigated. The success of the reaction is dramatically influenced by the choice of catalytic system: with nitrogen based nucleophiles the reaction works well with Pd₂(dba)₃/dppf, while with sulfur, oxygen and carbo-nucleophiles [Pd(η³-C₃H₅)Cl]₂/XPhos is more efficient. The regiochemical outcome shows that the nucleophilic substitution occurs only on the benzylic position of the η³-(benzofuryl)methyl complex. The high to excellent yields and the simplicity of the experimental procedure make this protocol a versatile synthetic tool for the preparation of 2-substituted benzo[b]furans.