Dynamic Equilibria between Pentavalent Protonated Oxyphosphoranes and Their Isomeric Tetravalent Enol Phosphonium Ions via Inter- and Intramolecular Proton Transfer

Article abstract of DOI:10.1021/jo00314a010

Low-temperature NMR (1H, 13C, 31P) measurements of the reaction of several pentavalent oxyphosphoranes with FSO3H in CH2Cl2 are described.Rapid equilibria between the neutral oxyphosphoranes and the enol phosphonium ions involving an intermolecular proton transfer can be obtained by implying certain structural constraints on the system, which means that less entropy has to be expended in order to obtain the rigid closed form of the protonated oxyphosphorane.Moreover, in one case evidence is presented for an intramolecular proton-exchange process which is also controlled by an intermediary pentavalent protonated oxyphosphorane.These reactions may be regarded as a model for intramolecular (biological) phosphorylation processes.