Stoichiometry-controlled cycloaddition of azomethine ylide with dipolarophiles: chemoselective and regioselective synthesis of bis- and tris-spirooxindole derivatives

A new series of bis- and tris-spirooxindole derivatives have been synthesized by controlling the molar equivalent of in situ generated azomethine ylides in [3+2]-cycloaddition reactions with dipolarophiles. The structural elucidation on the basis of IR, 1H NMR, 13C NMR, and mass spectral data of these compounds established the highly chemoselective and regioselective formation of spirooxindole derivatives. Single crystal X-ray analysis of compound 4g and 2D NMR analysis of compound 5a confirmed the structures of bis- and tris-spirooxindole derivatives.