ChemInform Abstract: Organocatalytic Tandem Enantioselective Michael—Cyclization of Isatin‐Derived β,γ‐Unsaturated α‐Ketoesters with 3‐Hydroxy‐4H‐chromen‐4‐one or 2‐Hydroxy‐1,4‐naphthoquinone Derivatives.

Abstract

The enantioselective formal [3 + 3] annulation reaction of isatin-derived β,γ-unsaturated α-ketoesters with 3-hydroxy-4H-chromen-4-ones or 2-hydroxy-1,4-naphthoquinone was successfully implemented under catalysis of quinine-derived bifunctional tertiary amine-thiourea catalysts. The efficient tandem Michael-cyclization has provided facile access to optically active spiro[oxindole-pyrano[3,2-b]chromenone] and spiro[oxindole-benzo[g]chromene-dione] derivatives in high yields with excellent diastereo- and enantioselectivities.