Highly efficient synthesis of spiro[oxazolidine-2-thione-oxindoles] with 3-isothiocyanato oxindoles and aldehydes via an organocatalytic cascade aldol-cyclization reaction

A highly efficient method for the construction of a family of spiro[oxazolidine-2-thione-oxindoles] with 3-isothiocyanato oxindoles and aldehydes via a cascade aldol-cyclization process has been developed. This method provides access to spiro[oxazolidine-2-thione-oxindole] derivatives bearing two vicinal quaternary/tertiary stereocenters in up to 95% yield, 98:2 dr, and 89% ee with a chiral bifunctional thiourea–tertiary amine organocatalyst based on DPEN scaffold. Good reactivity was observed and the reaction could be completed within 1.0 min.