Reaction of phosphites with unsaturated acid chlorides: synthesis and reactions of dimethyl but-2-enoylphosphonate

Abstract

Dimethyl trans-but-2-enoylphosphonate has been prepared in moderate yield from the reaction of trimethyl phosphite with excess of trans-but-2-enoyl chloride. When the reaction is carried out using equimolar quantities of reactants the major products is the trans-but-2-enoyl ester (5). This ester is formed by the facile reaction of the trans-but-2-enoyl phosphonate with trimethyl phosphite to give the pentacovalent oxaphospholen (6) which is then attacked by trans-but-2-enoyl chloride. The reactions of trialkyl phosphites with 2-methylpropenoyl and propenoyl chlorides follow similar pathways but at different relative rates.