合成路线1

The reaction of 2-methyl-4-(trifluoromethyl)aniline (I) with ethoxalyl chloride (II) by means of triethylamine in ethyl acetate gives the oxamic ester (III), which is nitrated at the aromatic ring with KNO3 and H2SO4 yielding the intermediate (IV). The reductocyclization of (IV) by means of TiCl3 in acetone affords the quinoxalinedione (V), which is treated with PCl5 in refluxing POCl3 affording the dichloroquinoxaline (VI). The reaction of (VI) with sodium methoxide in refluxing methanol gives the dimethoxyquinoxaline (VII), which is brominated with NBS and AIBN in refluxing benzene yielding the bromomethyl quinoxaline (VIII). The condensation of (VIII) with dimethyl 1(S)-aminoethylphosphonate (IX) by means of NaHCO3 in DMF affords the phosphonate derivative (X), which is finally submitted to acid hydrolysis to provide the target compound.