Mechanism of P-H insertion of α-imino copper carbenes: 1,1-Insertion or 1,3-insertion?

[Display omitted] •The P-H insertion of α-imino copper carbenes preferred to 1,3-insertion pathway.•The p-p and π-π packing interactions had positive effects for phosphinous acids.•The electron-withdrawing substituent of diphenylphosphinous acids were evaluated. The reaction mechanisms of P-H insertion of α -imino copper carbenes with H-phosphine oxides were theoretically investigated by the density functional theory (DFT). The results revealed that 1,3-insertion was the most preferred pathway due to the strong proton capture ability of the Schiff base, which lowered the energy barrier of P-H insertion. In addition, the effects of substituents on the reactivity of H-phosphine oxides were investigated. For phosphinous acids, the intermolecular p-p interaction and π-π packing interaction of phosphine oxide exhibited positive effects on the reactivity. For diphenylphosphinous acids, the electron-withdrawing substituent resulted in improving the reactivity of diphenylphosphinous acids.