Mechanism of Phosphorus-Carbon Bond Formation in the Amidoalkylation of Phosphonous Carboxylic Acids.

An unusual greater reactivity of phosphonous propionic acids was found in comparison with phosphonous propionic esters in carbamate version of Kabachnik-Fields reaction. Compounds of tricoordinated phosphorus generated during the amidoalkylation of hydrophosphorylic compounds in acetyl chloride/acetic anhydride mixture were found by P NMR analysis. A hypothesis is proposed about the generation of spirophosphoranes to explain the mechanism for the formation of the phosphorus-carbon bond in the reaction under study.