Dual Behavior of Isatin-Based Cyclic Ketimines with Dicarbomethoxy Carbene: Expedient Synthesis of Highly Functionalized Spirooxindolyl Oxazolidines and Pyrrolines

A highly stereo-, regio-, and chemoselective method has been devised for the synthesis of a wide range of spirooxindolyl oxazolidines via an intermolecular 1,3-dipolar cycloaddition of carbonyl ylides generated from dimethyl diazomalonate and aromatic aldehydes, with cyclic ketimines using 5 mol % of Rh₂(OAc)₄ under mild conditions. Similarly, highly functionalized spirooxindolyl pyrrolines have also been prepared through 1,3-dipolar cycloaddition of azomethine ylides generated from dimethyl diazomalonate and cyclic ketimines, with dimethyl acetylenedicarboxylate