Asymmetric synthesis of spirofuro[2,3-b]azepine-5,3′-indoline derivatives via cycloisomerization/[4 + 3] annulation process under Au/N-heterocyclic carbene relay catalysis†

Abstract

A variety of enantioenriched spirofuro[2,3-b]azepine-5,3′-indoline derivatives (dr > 20 : 1, up to 96% ee) were facilely synthesized through cycloisomerization/asymmetric formal [4 + 3] cycloaddition reactions of enyne-amides with isatin-derived enals under gold(i)/chiral N-heterocyclic carbene (NHC) relay catalysis. The method is practical and useful because of the convenient one-step procedure, high stereoselectivity, and good functional-group tolerance.