Bifunctional N-heterocyclic carbene catalyzed [3 + 4] annulation of enals with azadienes: enantioselective synthesis of benzofuroazepinones†
Abstract
The bifunctional N-heterocyclic carbene catalyzed [3 + 4] annulation of acyclic enals with aurone-derived azadienes was reported. The challenging β,β-disubstituted enals and β-monosubstituted enals reacted well to afford the corresponding benzofuroazepinones in good yields with excellent stereoselectivities. The bifunctional carbene with a free hydroxy group is the key factor for success.