Organo-catalyzed asymmetric cascade annulation reaction for the construction of bi-spirocyclic pyrazolone and oxindole derivatives

Abstract

A bifunctional organocatalyst catalyzed tandem annulation reaction between β,γ-unsaturated α-ketoesters with α-arylidene pyrazolinones was reported. The tandem Michael–aldol process allows access to optically active bi-spirocyclic pyrazolone and oxindole compounds in high yields with good to excellent enantioselectivity and diastereoselectivity. The resulting bi-spirocyclic compounds possess highly dense functionalized substituents, two all-carbon spiro quaternary stereocenters and one hemiketal stereogenic centers.