The first step in this reaction is the formation of an imine, followed by a hydrophosphonylation step where the phosphonate P-H bond across the C=N double bond.[5] The starting carbonyl component is usually an aldehyde and sometimes a ketone. The reaction can be accelerated with a combination of dehydrating reagent and Lewis acid.
Enantioselective variants of the Kabachnik-Fields reaction have been developed, for example employing α-methylbenzylamine provides a chiral, non-racemic α-aminophosphonate.[6]
^Gilmore, F.; McBride, A. (1972). "Synthesis of an optically active -aminophosphonic acid". J. Am. Chem. Soc. 94 (12): 4361. doi:10.1021/ja00767a065. PMID5036657.