Theoretical study of a derivative of chlorophosphine with aliphatic and aromatic Grignard reagents: S N 2@P or the novel S N 2@Cl followed by S N 2@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.