Simple and effective synthesis of functionalized (hydroxymethylene)bis(phosphonic) acids

‘Technical’ tris(trimethylsilyl) phosphite, (Me₃SiO)₃P, as a mixture with (Me₃SiO)₂P(O)H and (Me₃SiO)₃P(O) (71 : 20 : 9) was obtained upon the action of (Me Si) NH on phosphorous acid H₃PO₃ in the presence of catalytic amount of Me₃SiCl. The action of this material on acid chlorides RC(O)Cl affords (hydroxymethylene)bis(phosphonic) acids RC(OH)[P(O)(OH)₂]₂ in preparative yields.