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

Abstract

The formation of phosphate diesters (RO)₂P(X)OH (R = Et, Prⁱ or Prⁱ₂CH) by phosphorylation of ROH with ROP(X)(NPrⁱ₂)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_N2(P) mechanism when X = O.