Synthesis of phosphonates from phenylphosphonic acid and its monoesters

Possibilities for the mono- and diesterification of phenylphosphonic acid were evaluated considering the microwave(MW)-assisted direct esterification, and the alkylating esterification. It was found that regarding the monoesterification, the reaction with 15-fold alcohol excess in the presence of [bmim][BF4] additive utilizing MWs is superior than the approach by alkylation. At the same time, for the conversion of the monoester intermediate to the diester, the reaction with alkyl halides in the presence of triethylamine as the base, again under MW irradiation, was found to be the method of choice. Phosphonates with both identical and different alkoxy groups were made available. [GRAPHICS]