I. Lukeš, M. Borbaruah, L. D. Quin:
"Direct Reaction of Phosphorus Acids with Hydroxy of a Silanol and on the Silica Gel Surface."
J. Am. Chem. Soc. 116, (1994) 1737-41
► DOI: 10.1021/ja00084a014, ► PDF
Several phosphorus acids (methyl- and phenylphosphonic, diphenylphosphinic, and Et phosphoric acids) were found to give esters on reaction with
tert-butyldimethylsilanol.The reactions occurred simply on heating the reactants in an inert solvent (hexane or toluene). The reaction is reversible, and yields of esters were improved by continuous water removal. The dibasic acids gave either mono- or disilyl esters: the latter were more easily purified and characterized. The OH groups on the surface of silica gel were also found to react with various phosphorus acids under similar conditions to give surface-bonded esters. Products were characterized by CP/MAS 31P and 29Si NMR.In the case of phenylphosphonic acid and Et phosphoric acids, the products were spectrally identical with those obtained by phosphorylation of the surface OH groups with the highly reactive 3-coordinateanhydrides of these acids when generated in the presence of silica gel.