Differential reactivity of β-amino enones and 3-dimethylaminoacrylaldehyde towards α-amino derivatives

Unsubstituted β-amino enones react with α-amino derivatives by a well established route which implies a fast transamination process — 1,4-addition followed by elimination — and cyclodehydration of the intermediate to 3-functionalized pyrroles. In contrast, 3-dimethylaminoacrylaldehyde undergoes 1,2-addition followed by cyclization to give the final 2-substituted pyrroles. Isolation of the intermediates supports the proposed mechanism for each reaction.