Theoretical study of a derivative of chlorophosphine with aliphatic and aromatic Grignard reagents: SN2@P or the novel SN2@Cl followed by SN2@C?

The proposed S(N)2 reactions of a hindered organophosphorus reactant with aliphatic and aromatic nucleophiles [Ye et al., Org. Lett., 2017, 19, 5384-5387] were studied theoretically in order to explain the observed stereochemistry of the products. Our computations (using B3LYP as the functional) indicate that the reaction with the aliphatic nucleophile occurs through a backside S(N)2@P pathway while the reaction with the aromatic nucleophile proceeds through a novel S(N)2@Cl mechanism, followed by a frontside S(N)2@C mechanism.