Theoretical Investigation on the Mechanism of Michael Addition of Malononitrile to α,β-unsatuated ketones Catalyzed by quinidine

초록

The mechanism of Michael addition of malononitrile to α,β-unsatuated ketones catalyzed by primary amines derived from quinidine was investigated by DFT method with 6-31+G* basis set. The computational results indicate that ketone substrates could be activated by generating reactive iminium ion intermediates through primary amine group of quinidine. The tertiary amine in quinidine could work as Lewis base to promote the activation of malononitrile and deprotonation. Two continued stages are involved in the overall reaction: (i) the formation of iminium ion intermediates; (ii) the addition reaction between iminium ion and Malononitrile. The step corresponding to the transfer of H atom from quinoline unite to C atom of ketone was predicted to be the rate-determining step.