Squaramide-Catalyzed Asymmetric Michael/Cyclization Cascade Reaction of Unsaturated Thiazolidinones and 3-Isothiocyanato Oxindoles: Synthesis of New Bispirocyclic Heterocycles

Abstract

A highly efficient method for the construction of oxindole-pyrrolidone-thiazolidinone bispirocyclic heterocycles bearing three contiguous chiral centers including two quaternary one via a Michael/cyclization cascade reaction has been developed. Using bifunctional cinchona-derived squaramide as catalyst, the reactions of 3-isothio­cyanato oxindoles with unsaturated thiazolidinone derivatives proceeded smoothly under mild reaction conditions to afford a series of complex chiral oxindole-pyrrolidone-thiazolidinone bispirocyclic heterocycles in high yields (up to 99%) with excellent diastereo- and enantioselectivities (up to >99:1 dr, >99% ee).