Asymmetric Aza-Michael Reactions Catalyzed by Cinchona Alkaloids

The organocatalysed asymmetric aza-Michael addition of
hydrazones to cyclic enones has been achieved in good yield
and stereoselection using cheap and commercially available
cinchona alkaloids as catalysts. A systematic study of the
influence of the structure of the enone on the stereoselectivity
was carried out, leading to optically active products with up
to 77% ee. The products can be recrystallized to give nearly
enantiopure products, and furthermore it was shown that the
products could be reduced to the corresponding 1,3-benzylidenehydrazino alcohol derivatives with high diastereoselectivity.