Synthesis of Cyclohexanones via Double-Conjugate Addition of Dienones

Significance

Yan and co-workers report an asymmetric double-conjugate addition of malononitrile 2 to dienones 1. Using 9-amino-9-deoxy­epiquinine 3 as catalyst and TFA as a co-catalyst, a series of 3,4,4,5-tetrasubstituted cyclohexan­ones 4 were obtained in good yields and excellent enantioselectivities. Both electron-donating and -withdrawing substituents at the aryl group were well tolerated. However, monoalkyl-substituted or dialkyl dienones showed low or no reactivity under these reaction conditions. Takemoto’s bifunctional catalyst 5 could also promote the reaction, though with lower enantioselectivity (60% ee) and lower yield (25%), while its primary amine analogue 6 did not show any catalytic activity under the same ­reaction conditions.