Multicomponent reactions of phosphines, enynedioates and cinnamaldimines give γ-lactams with a 1,3,5-hexatriene moiety for facile 6π electrocyclization: Access to oxindoles, isatins and isoxazolinones

Abstract

Multicomponent reactions of phosphines, enynedioates and cinnamaldimines generated 3-phosphorus ylide γ-lactams having a 1,3,5-hexatriene moiety with low activation energy barrier for 6π electrocyclization, through initial formation of 1,3-dipoles from the α(δ')-Michael addition of phosphines to enynedioates. The reactive 1,3-dipoles underwent addition to cinnamaldimines, lactamization, 6π electrocyclization and oxidation to give 3-phosphorus ylide oxindoles as platform molecules toward isatins and isoxazolinones. The key step, 6π electrocyclization, was further examined by a kinetic and a computational study.