Organophosphorus chemistry. Part 1. The synthesis of alkyl methylphosphonic acids

Abstract

Several alkyl hydrogen methylphosphonates of structure RO(HO)P(O)Me were synthesised by a three-stage route [R = i-Pr, n-Bu, i-Bu, s-Bu, pinacolyl Me₃C-CH(Me)-, cyclopentyl and cyclohexyl]. Trimethyl phosphite was transesterified with alcohols in the presence of sodium catalyst to give the mixed phosphites (MeO)₂POR in 6–64% yield. Treatment of these with methyl iodide gave alkyl methyl methylphosphonates RO(MeO)P(O)Me in 66–95% yield. Selective demethylation of these compounds by bromotrimethylsilane, followed by methanolysis of the phosphorus silyl esters RO(Me₃SiO)P(O)Me, gave the hydrogen phosphonates in 60–97% yield.