Organocatalytic Michael/cyclization cascade reactions of 3-isothiocyanato oxindoles with 3-trifluoroethylidene oxindoles: an approach for the synthesis of 3 '-trifluoromethyl substituted 3,2 '-pyrrolidinyl-bispirooxindoles

摘要

An efficient asymmetric Michael/cyclization cascade reaction of 3-isothiocyanato oxindoles with 3-trifluoroethylidene oxindoles has been revealed. Under bifunctional organocatalysis with a cinchona alkaloid derived squaramide catalyst, a series of novel 3'-trifluoromethyl substituted 3,2'-pyrrolidinyl-bispirooxindoles were conveniently constructed in a highly stereoselective manner (up to 96% yield, 20 : 1 dr and 99% ee). The reaction leads to the formation of three contiguous stereogenic centers and two spiro quaternary stereocenters.