Abstract
| - A new catalytic enantioselective conjugate addition of nitroalkanes to acyclic α,β-unsaturated enonescatalyzed by novel organic catalysts has been developed. A series of chiral amines has been testedas catalysts for the addition of 2-nitropropane to benzylideneacetone, and it is found that a novelimidazoline catalyst, prepared from phenylalanine, can catalyze a highly enantioselective 1,4-addition reaction. The reaction of various acyclic and cyclic nitroalkanes was found to proceed wellwith enantioselectivities up to 86% ee, and enantiopure products can be obtained by recrystallization.The potential of the reaction is documented by the reaction of a series of substituted α,β-unsaturatedenones with different nitroalkanes. Furthermore, the synthetic applicability of the reaction isdemonstrated by the formation of optically active functionalized pyrrolines and pyrrolidines byreductive amination of the products. On the basis of the absolute configuration of the conjugateaddition products, the mechanism for the reaction is discussed and a transition state proposed.
|