Facile high yielding synthesis of symmetric esters of methylenebisphosphonic acid

The 1H-tetrazole catalyzed coupling of methylenebis(phosphonic dichloride), CH2(POCl2)2, with primary alkyl, cyclic secondary alkyl, aromatic, and silicon- and fluorine-containing alcohols selectively affords symmetric P,P′-dialkyl partial esters as well as homoleptic and mixed tetraesters. Two partial ester intermediates, methylenebis(2-ethylhexyl phosphonic chloride) and 2-ethylhexyl methylenebisphosphonic trichloride, were observed by 1H- and 31P NMR spectroscopy in the esterification of CH2(POCl2)2 with 2-ethyl-1-hexanol.