Multicomponent Reactions of Phosphines, Enynedioates and Cinnamaldimines Give gamma-Lactams with a 1,3,5-Hexatriene Moiety for Facile 6 pi Electrocyclization: Access to Oxindoles, Isatins and Isoxazolinones

Abstract

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