Organocatalytic Asymmetric Michael Addition of Pyrazolin‐5‐ones to Nitroolefins with Bifunctional Thiourea: Stereocontrolled Construction of Contiguous Quaternary and Tertiary Stereocenters

The first organocatalytic diastereo‐ and enantioselective Michael addition reaction of 4‐substituted‐pyrazolin‐5‐ones to nitroolefins has been developed with a chiral bifunctional thiourea as organocatalyst. A wide variety of desired multi‐substituted pyrazolin‐5‐one derivatives with contiguous quaternary and tertiary stereocenters are smoothly obtained in very good yields (up to 98%) with excellent enantioselectivities (up to>99% ee ) and acceptable diastereoselectivities (up to 80:20). This experimentally simple process facilitates the access to various enantioenriched, multiply substituted pyrazolin‐5‐one derivatives, potential biologically active molecules, starting from readily available starting materials.