Enamines, 1, prepared from cyclohexanones or cyclopentanones are reacted with acrylamide to give lactams, the condensed 2-piperidones, 2. Ethyl 2-(1-pyrrolidinyl)-2- cyclohexene-1-propanoate, 3, when treated with primary amines, produces the corresponding N-substituted 2-piperidones, 4. Ethyl 2-(1-pyrrolidinyl)-2-cyclohexene-1- ethanoates and ethyl 2-(1-pyrrolidinyl)-2-cyclopentene-1-ethanoate, 5, react with primary ...