Ring chain transformation of γ-keto-δ-crotonolactones: A convenient synthesis of 1,4-piperazinones, 1,4-thiazinones and 1,4-diazepinones

A new procedure for the efficient synthesis of 1,4-piperazinones, 1,4-thiazinones and 1,4-diazepinones is presented. The reaction is based on a ring chain transformation of γ-keto-δ-crotonolactones induced by 1,2- or 1,3-diamino- (or thiamino-) binucleophiles. The reaction sequence of this transformation is also discussed.