Synthesis of Chiral Allylic Phosphine Oxides

Significance

In the presence of arylboronic acids and a Rh(OH)(R-BINAP) catalyst system, a variety of phosphinylallenes were converted into chiral allylic phosphine oxides in good to excellent yields and enantioselectivities. The enantioselectivity is not affected by the electronic nature of the boronic acid; however, the steric bulk of R has a profound effect on both enantioselectivity and the yield of the desired product. Where R = t-Bu, no desired product was formed, and only achiral vinyl phosphine oxide was obtained. Addition occurs at the central carbon of the allene, followed by regio- and enantioselective protonation.