Synthesis of 3-Aryl- and 3-Alkynylbenzofurans in the Presence of a Supported Palladium Catalyst

Abstract

AbstractSuzuki and Sonogashira coupling reactions of 3-iodo-2-phenylbenzofuran, leading to the corresponding 3-aryl- and 3-alkynyl derivatives, respectively, were carried out using a silica supported pyridinium ionic liquid-based heterogeneous catalyst. Under optimized reaction conditions, arylboronic acids with either electron-withdrawing or -donating substituents as well as terminal alkynes with aromatic or aliphatic groups could be coupled to the benzofuran skeleton efficiently. The application of this catalyst made it possible to carry out the reaction under phosphine-free and, in the case of the Sonogashira coupling, under copper-free conditions. The catalyst retained its activity in at least 7 subsequent runs in both types of reactions. Palladium leaching of less than 1% of the original amount used in the catalytic reaction was observed under optimized conditions in most cases. The methodology was applied successfully to the synthesis of nine different 3-aryl- and ten different 3-alkynylbenzofuran derivatives in moderate to high yields.