Studies on aryl H-phosphonates. 3. Mechanistic investigations related to the disproportionation of diphenyl H-phosphonate under anhydrous basic conditions

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Diphenyl H-phosphonate undergoes under anhydrous reaction conditions a base-promoted disproportionation to triphenyl phosphite and phenyl H-phosphonate. On the basis of 31P NMR data the most likely mechanism for this transformation was proposed. In order to substantiate these findings and to get a deeper insight into the chemistry of aryl H-phosphonate esters, we carried out also some studies on activation of phenyl and diphenyl H-phosphonates with various condensing agents. We found that aryl vs alkyl esters of phosphonic acid often follow different reaction pathways during the activation, and this can most likely be traced back to higher electrophilicity of the phosphorus centre and to higher reactivity of the P-H bonds in aryl H-phosphonate derivatives.