Highly stereoselective synthesis of spiropyrazolones

Abstract

The synthesis of spiro compounds through a Michael-Michael-aldol reaction is reported. The reaction affords spiropyrazolone derivatives in good yields, in almost diastereo- and enantiopure form, and is catalyzed by diphenylprolinol derivatives. The reaction showed strong nonlinear effects. Remarkably, when a catalyst with 70 ee is used, the reaction still affords the final spiro compound in almost diastereo- and enantiopure form. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.