Organocatalytic Asymmetric Synthesis of Tetrasubstituted Axially Chiral Allenylphosphines

Albeit notable endeavors in enantioselective allenyl C–X bond formation reactions (X = C, O, S, Si, etc.), the catalytic asymmetric synthesis of tetrasubstituted axially chiral allenylphosphines via C–P bond formation still stands for a long-lasting challenge. Herein, we report an intriguing chiral phosphoric acid (CPA)-catalyzed asymmetric 1,8-addition reaction between tertiary propargylic alcohol derivatives and H-phosphine oxides, which enables the synthesis of a series of tetrasubstituted axially chiral allenylphosphines through the construction of C–P bonds in good yields with high stereoselectivity. Avoiding the use of transition metals, this method represents a unique example of organocatalytic asymmetric axially chiral allenyl C–P bond formation, showcasing the extraordinary potential of the organocatalytic asymmetric synthesis of fully substituted allenes. Control experiments and density functional theory calculations suggested that the process involves the in situ generation of imine methide intermediate and efficient remote control of regioselectivity and enantioselectivity by a bifunctional CPA catalyst.