Reactivity of Primary Phosphines and Primary Phosphine Sulfides towards Imines

Reactivity of primary phosphines with two stoichiometric equivalents of imine results in the formation of bis-alpha-aminophosphines (2 a-e), which can be subsequently oxidized in the presence of S-8 or H2O2 to generate air stable bis-alpha-aminophosphine sulfides (2 b-m(S/O)). To elucidate the mechanism of this three-component reaction, Hammett analysis, kinetic isotope effect (KIE), and trapping experiments were performed. Ultimately a P(V)-P(III) tautomerization is invoked, followed by nucleophilic attack by the P(III) species to generate the desired products.