Catalytic Asymmetric P-H Insertion Reactions

Albeit notable endeavors in enantioselective carbene insertion into X-H bonds (X = C, O, N, S, Si, B), the catalytic asymmetric P-H insertion reactions still stand for a long-lasting challenge. By merging transition-metal catalysis with organocatalysis, we achieve a scalable enantioselective P-H insertion transformation between diazo pyrazoleamides and H-phosphine oxides that upon subsequent reduction delivers a wide variety of optically active β-hydroxyl phosphine oxides in good yields with high enantioselectivity. The achiral copper catalyst fosters the carbenoid insertion into the P-H bond, while the chiral cinchona alkaloid-derived organocatalyst controls the subsequent enantioselective outcome. Density functional theory (DFT) calculations further reveal that the copper catalyst chelates to the organocatalyst, enhances its acidity, and accordingly promotes the enantioselective proton transfer. Our work showcases the potential of combining transition-metal catalysis with organocatalysis to realize elusive asymmetric reactions.