Synthesis of functionalized diarylbenzofurans via Ru-catalyzed C–H activation and cyclization under air: rapid access to the polycyclic scaffold of diptoindonesin G

Abstract

An efficient method was developed for synthesis of 2,3-diarylbenzofuran-4-carboxylic acids from m-hydroxybenzoic acids and alkynes via Ru-catalyzed C–H alkenylation and aerobic annulation, in which air was employed as a mild oxidant. This method is compatible for various substrates with high regioselectivity for the C–H bonds. The obtained products can be transformed to polycyclic compounds via intramolecular Friedel–Crafts acylation. This protocol was successfully applied for total synthesis of diptoindonesin G, a natural product with a benzofuran-containing tetracyclic scaffold and potent biological activities.