Base promoted regio- and stereoselective hydrophosphinylation of allenes

A novel and transition-metal-free hydrophosphinylation of allenes with secondary phosphine oxides was developed. In the presence of the cheap and commercially available cesium carbonate, various hydrophosphinylation products were synthesized with exclusive regio- and stereoselectivity under mild conditions. This methodology provides simple and efficient access to (<i>E</i>)-alkenylphosphine oxides in moderate to excellent yields with a relatively broad substrate scope.