l-Isoleucine derived bifunctional phosphine catalyses asymmetric [3 + 2]-annulation of allenyl-esters and -ketones with ketimines

Abstract

The zwitterionic 1,3-dipoles generated by the addition of a bifunctional L-isoleucine derived N-acylaminophosphine to allenic esters as well as ketones were successfully trapped with isatin derived ketimines in a [3 + 2]-annulation reaction to deliver 3,2′-dihydropyrrolyl spirooxindoles in high yields (up to 88%) and with excellent enantioselectivities (up to >99%). The asymmetric annulation reaction provides a facile access to biologically relevant small molecules embodying the natural product spirocyclic core.