Multicomponent Reactions Initiated by the Michael Reaction

The first multicomponent reaction initiated by a Michael addition combining enamine and iminium ion activations was reported by j0rgensen et al., in 2005 

The mechanism proposed by the authors is depicted in this scheme. A first equivalent of a,fS-unsaturated aldehyde was activated as its corresponding iminium ion by chiral diphenylprolinol trimethylsilyl ether and then underwent the first nitromethane Michael addition to afford a nitroalkane enamine intermediate. Subsequent hydrolysis generated a nitroaldehyde intermediate and the catalyst, which could promote a second Michael addition with a second equivalent of iminium, furnishing an enamine intermediate. This enamine reacted via an intramolecular aldol cyclization to give a novel iminium intermediate. After hydrolysis, the catalyst was regenerated, and the intermediate alcohol could be dehydrated to afford the final products. 

2 Michael Reactions of Other x,P-Unsaturated Carbonyl Compounds 

---