Synthesis of Phosphonates with Identical and Different Alkyl Groups by the Microwave-Assisted Alkylation of Phosphonic Ester-Acid Derivatives.

Monoalkyl phosphonic derivatives obtained by the microwave (MW)- and ionic liquid-promoted direct esterification of alkylphosphonic acids were converted to the corresponding dialkyl alkylphosphonates on reaction with alkyl halides in the presence of triethylamine, under solvent-free MW-assisted conditions. Derivatives with different alkoxy groups were also synthesized. A minor "disproportionation" side reaction was identified during the preparation of dialkyl alkylphosphonates with different alkoxy groups. All together 12 alkylphosphonates were prepared by the efficient method developed.