Asymmetric Conjugate Addition of Unmodified Cyclic Ketones to Nitroolefins Using Aminophosphonate as the Organocatalyst

Abstract α ‐Aminophosphonates are an important class of compounds with diverse and useful biological activities. Despite that their structues are similar to that of proline, however, chiral cyclic α ‐aminophosphonates have found little applications in catalytic asymmetric synthesis. In this paper, an enantiopure α ‐aminophosphonate has been synthesized and was found to be effective as a chiral organocatalyst for the asymmetric conjugate addition of cycloketones to β ‐nitrostyrenes. With a catalyst loading of 20 mol% and in the presence of 10 mol% of CF 3 COOH as a cocatalyst, the Michael adducts could be obtained with varying degrees of diastereo‐ and enantioselectivities (up to 97:3 and 90% ee respectively) under solvent‐free conditions.