General procedure for the synthesis of diethyl carbamoylmethylphosphonate from chloroacetamide and triethyl phosphite: 2-chloroacetamide (5.01 g, 53.6 mmol) and triethyl phosphite (9.19 mL, 53.6 mmol) were dissolved in o-xylene (14 mL), and heated and refluxed for 3.5 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure to give a dark brown tarry residue. The residue was dissolved in dichloromethane and filtered through a short silica gel column. The filtrate was concentrated and the resulting solid was recrystallized with ethyl acetate/pentane mixed solvent to afford diethyl carbamoylmethylphosphonate (3.42 g, 33% yield) as light brown crystals. The structure of the product was analyzed by 1H NMR (200 MHz, DMSO-d6) δ 7.35 (br s, 1H), 7.02 (br s, 1H), 4.02 (dq, 4H, J = 7.1 Hz, JPH = 1.1 Hz), 2.80 (d, 2H, JPH = 21.4 Hz), 1.23 (t, 6H, J = 7.0 Hz); 13C NMR (50 MHz, DMSO-d6) δ 166.0 (d, 2JCP = 5.1 Hz), 61.5 (d, 2JCP = 6.0 Hz), 34.5 (d, 1JCP = 131.6 Hz), 16.2 (d, 3JCP = 6.0 Hz); 31P NMR (81 MHz, DMSO-d6) δ 23.8 confirmed. Mass spectrometry results: ESIMS m/z 218 [M + Na]+; high resolution mass spectrometry (HRMS) calculated value C6H14NO4P [M]+ 195.0655, measured value 195.0653.
