Acid-Catalyzed Solvolysis of Highly Reactive Phosphoramidates: A Stereochemical Study

Article abstract of DOI:10.1021/jo00385a019

Two 2-substituted-5-(chloromethyl)-1,3,2-dioxaphosphorinanes have been prepared in which the 2-substituent is either imidazole or benzimidazole.The two phosphoramidates in which the 2-substituent is axial have opposite configurations as determined by NMR and solvolysis studies.Acid-catalyzed methanolysis in both cases is extremely rapid and proceeds by 100percent inversion.However, with weak nucleophiles or a nucleophile kept in low concentration, an intermediate is formed which has enough lifetime to allow at least partial equilibration about the phosphorus atom.Although a completely free phosphacylium ion is unlikely, with aromatic solvents a similar product ratio from both isomers which may reflect a common intermediate is approached.