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

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).