Direct access to spirooxindole dihydropyrrole fused pyrazolones and bis-spiropyrazolone derivatives

Abstract

A highly regio- and diastereo-selective [3 + 2] annulation of Morita–Baylis–Hillman carbonates of isatins/pyrazolones with pyrazolone derived ketimines has been developed to access spiroheterocycles. The protocol worked effectively to construct spirooxindole dihydropyrrole fused pyrazolone and bis-spiropyrazolone dihydropyrrole derivatives bearing two vicinal quaternary spirocentres in good to excellent yields with very high diastereoselectivities under mild catalytic condition at room temperature. The protocol proved to be efficient with diverse MBH carbonates and ketimine derivatives. The method has successfully demonstrated the utility of DMAP as the commercially viable catalyst for this transformation.