Reactions of O,O'-dialkylthiophosphoric acids with acrylates provide a direct synthetic route to beta-carboxylated thiolophosphates. This Michael addition, without solvent, is quantitative at 90degreesC in 1 h for the 2/1 thiophosphoric acid/acrylate ratio. Moreover, this excess of thiophosphoric acid can be reused for further reactions. (C) 2003 Elsevier Ltd. All rights reserved.