Phosphoramidic acid monoesters as phosphorylating agents: steric effects and reluctance to form monomeric metaphosphate intermediates.

Abstract

The formation of phosphate diesters (RO)(2)P(X)OH (R = Et, Pr(i) or Pr(i)(2)CH) by phosphorylation of ROH with ROP(X)(NPr(i)(2))OH is insensitive to steric effects when X = S but not when X = O; this is consistent with a unimolecular mechanism and a thiometaphosphate (ROPOS) intermediate when X = S but a bimolecular S(N)2(P) mechanism when X = O.