Oxidative N-heterocyclic carbene-catalyzed [3 + 3] annulation reaction of enals with benzofuran-3-ones: efficient access to benzofuran-fused δ-lactones

Abstract

A facile route to benzofuran-fused δ-lactones was developed via an N-heterocyclic carbene-catalyzed [3 + 3] annulation reaction, giving the expected products in high yields (up to 99%) with excellent enantioselectivities (up to 98% ee). It should be noted that benzofuran-fused pyrones can be obtained stepwise in one pot with excellent yields (up to 96%) by using this methodology.