A process for the synthesis of a hydrocarbylvinyl-1-phosphonic acid hydrocarbyl ester, such as a 1-phenylvinylphosphonic acid dialkyl ester, which utilizes: (a) the base catalyzed addition (preferably using a nonnucleophilic strong organic base) of a hydrocarbyl phosphite, such as a dialkyl phosphite containing no more than about eight carbon atoms in either of its alkyl groups, to an aldehyde or methyl ketone, such as a phenyl ketone, as exemplified by acetophenone, to form a hydrocarbyl 1-hydroxy-1-hydrocarbylphosphonate, such as a dialkyl 1-hydroxy-1-phenylalkylphosphonate compound; (b) the acid-catalyzed esterification (preferably acetylation) of the compound from (a) with an acid anhydride to form an acylated intermediate; and (c) the removal of carboxylic acid (preferably at a temperature of from about 50° C. to about 215° C. under reduced or atmospheric pressure) from the intermediate from (b) to form the desired hydrocarbylvinylphosphonic acid hydrocarbyl ester, such as a 1-phenylvinylphosphonic acid dialkyl ester.