A systematic study of reaction of heterocyclic enamines with electrophilic alkynes: A simple and efficient synthetic route to 2- pyridinone-fused heterocycles

Article abstract of DOI:10.1016/S0040-4020(99)00937-0

The reaction of heterocyclic enamines with ethyl propiolate and diethyl acetylenedicarboxylate has been systematically studied. In contrast to their heterocyclic ketene aminal analogues, heterocyclic enamines reacted with electrophilic alkynes via the Michael addition pathway rather than the aza- ene reaction mechanism. In the presence of a strong base such as sodium ethoxide and sodium hydride, the resulting Michael addition products underwent cyclocondensation reaction readily to produce 2-pyridinone-fused heterocycles in good to excellent yield.