Dithiophosphinylation of Allenyl Acetates: Access to 1,2-Bis(diphenylphosphino)ethane-Type Bidentate Ligands.

1,2-Bis(diphenylphosphino)ethanes (DPPEs) are versatile and immensely important ligands in transition metal catalysts. Here we report the dithiophosphinylation of readily available allenyl acetates to give DPPEs in high yields and regioselectivity. This protocol features a broad substrate scope and mild conditions, avoiding the use of transition metals and air-sensitive sources of phosphorus. Mechanism studies indicate that the reaction was accomplished via an S N 2'-type addition-elimination followed by a 1,4-addition step.