INVESTIGATIONS OF THE NUCLEOPHILIC DISPLACEMENT AT THE TETRAHEDRAL PHOSPHORUS - KINETIC EFFECTS OF THE NUCLEOPHILE FOR A GIVEN STEREOCHEMISTRY.

Article abstract of DOI:10.1016/S0040-4020(01)88163-1

A kinetic study of alcoholysis and aminolysis of 2-chloro-2-oxo-1,3,2-dioxaphospholane, 1, shows a rate levelling effect of the nucleophile, where the stereochemistry is retention at phosphorus.On the other hand, the substitutions with inversion of the 2-chloro-2-oxo-1,3,2-dioxaphosphorinane 2, or the diethylchlorophosphate, 3, show a marked influence of the nucleophile upon the reactivity.Furthermore, the large rate increase which has been observed for the hydrolysis of the five-membered ring phosphorus esters compared to phosphates (an oxygen always displaces an oxygen) is not reproduced when the leaving group is different of the nucleophile.We suggest that the mechanistic implications, established in the case of phosphate esters hydrolysis cannot be directly extended to the general case of S^N2(P).The mechanism of nucleophilic substitution of P(4) species is better interpreted in terms of HOMO-LUMO interactions between the nucleophile and the substrate, a process now well established in silicon chemistry.