Enantio- and diastereoselective synthesis of spiropyrazolones via an organocatalytic [1 + 2 + 3] multicomponent reaction.

An asymmetric catalytic multicomponent reaction of malononitrile, benzaldehyde, and α-arylidene pyrazolinones to produce spiropyrazolones has been reported. The [1 + 2 + 3] multicomponent reaction was catalyzed by chiral cinchona alkaloids to provide spiropyrazolones in high yields, with excellent enantioselectivities and good diastereoselectivities. We also performed control experiments and proposed a plausible catalytic cycle based on the observed experimental results to explain the reaction process and stereoselectivity of the asymmetric multicomponent reaction.