Formal [4+2] annulation of enaminones and cyanomethyl sulfur ylide: one-pot access to polysubstituted pyridin-2(1H)-ones

A facile and efficient one-pot synthesis of polysubstituted pyridin-2(1H)-ones from readily available enaminones and the cyanomethyl sulfonium bromide salt in the presence of cesium carbonate is developed, and a mechanism involving sequential nucleophilic vinylic substitution (S(N)V), intramolecular nucleophilic cyclization and dealkylation reactions is proposed.