A new method for the preparation of tetraalkyl ethenylidenebis(phosphonates) has been developed. This two-step procedure involves the base-catalyzed reaction of a methylenebis(phosphonate) ester with paraformaldehyde followed by acid-catalyzed elimination of methanol. The effecta of variations in the reaction conditions of the first step of this process are described. Ethenylidenebis(phosph0nate) esters can be converted to the free acid by reaction with bromotrimethylsilane.Ethenylidenebis(phosph0nic acid) (1) and its esters have found utility as sequestering agents,' in the development of polymeric flame retardants,2 and in certain pharmaceutical application^.^ Currently, ethenylidenebis(ph0s-Registry No.

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The diol ditosylates (I) undergo ring closure reaction with tetraisopropyl methylenebisphosphonate (II) in toluene to give the tetraisopropyl cycloalkane‐1,1‐bisphosphonates (III) which are hydrolyzed with hydrochloric acid to form the cycloalkane‐1,1‐bisphosphonic acids (IV).

A two‐step procedure for the formation of the tetraesters (IV) from the bisphosphonates (I) and excess paraformaldehyde (II) in methanol is presented.