Organocatalyzed Diastereo‐ and Enantioselective Conjugate Addition of Nitroalkanes to β‐Silylmethylene Malonates: Direct Access to Enantioenriched Organosilanes

Abstract

Cinchona‐alkaloid derived bifunctional thiourea catalyzed conjugate addition reaction of nitroalkanes to β‐silylmethylene malonates is reported for direct access of densely functionalized enantioenriched organosilanes in good yields (up to 86 %) with excellent stereoselectivities (up to 98:2 dr and 90 % ee). Using pseudoenantiomeric catalyst, both the enantiomers of the conjugate addition products were easily accessible. Preparative scale synthesis of two conjugate addition products confirmed the practical applicability of the current methods. Furthermore, the synthetic potential of these organosilanes was demonstrated by employing one of the products in the formal asymmetric synthesis of the nootropic drug (R)‐oxiracetam, the synthesis of sila‐analogue of PAR‐2 agonist AC‐264613, and the synthesis of (R)‐N‐benzyl‐4‐hydroxy‐pyrrolidin‐2‐one, intermediate for the synthesis of several pharmaceuticals.