A general reagent for O-phosphonomethylation of phenols

Abstract

Diethyl 4-chlorophenylsulfonyloxymethylphosphonate, ClC₆H₄SO₂OCH₂P(O)(OEt)₂, has been established as the reagent of choice for conversion of phenols via alkali phenoxides into phenoxymethylphosphonates. With other leaving groups (iodide, methanesulfonate, toluene-4-sulfonate), or with the dimethyl instead of the diethyl ester, concomitant formation of alkyl phenyl ethers reduced the yields. The reactions proceeded easily in polar aprotic solvents, usually at room temperature, and yields were excellent. The products were easily converted by mild alkaline hydrolysis into monoesters, or into phosphoric acids via cleavage with iodotrimethylsilane. Some phenols were also converted into diethyl aryloxymethylphosphonates by incorporation into mixed formals by reaction with 2,4-dichlorophenoxymethyl chloride, followed by Lewis acid-catalysed transfer of an aryloxymethyl group to triethyl phosphite.