The partial hydrolysis ot 2,3,4-trifluoronitrobenzene (I) with KOH in DMSO gives 2,3-difluoro-6-nitrophenol (II), which by condensation with chloroacetone (III) by means of K2CO3 - KI in refluxing acetone yields 2-acetonyloxy-3,4-difluoronitrobenzene (IV). The reductive cyclization of (IV) with H2 over Raney-Ni in ethanol affords 7,8-difluoro-2,3-dihydro-3-methyl-4H-benzoxazine (V), which is condensed with diethyl ethoxymethylenemalonate (VI) by heating at 145 C giving the malonic derivative (VII). The cyclization of (VII) by heating at 145 C with ethyl polyphosphate (PPE) yields ethyl 9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylate (VIII), which is hydrolyzed with HCl in refluxing acetic acid affording the corresponding free acid (IX). Finally, this compound is condensed with N-methylpiperazine (X) in DMSO at 110 C.

The partial hydrolysis ot 2,3,4-trifluoronitrobenzene (I) with KOH in DMSO gives 2,3-difluoro-6-nitrophenol (II), which by condensation with chloroacetone (III) by means of K2CO3 - KI in refluxing acetone yields 2-acetonyloxy-3,4-difluoronitrobenzene (IV). The reductive cyclization of (IV) with H2 over Raney-Ni in ethanol affords 7,8-difluoro-2,3-dihydro-3-methyl-4H-benzoxazine (V), which is condensed with diethyl ethoxymethylenemalonate (VI) by heating at 145 C giving the malonic derivative (VII). The cyclization of (VII) by heating at 145 C with ethyl polyphosphate (PPE) yields ethyl 9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylate (VIII), which is hydrolyzed with HCl in refluxing acetic acid affording the corresponding free acid (IX). Finally, this compound is condensed with N-methylpiperazine (X) in DMSO at 110 C.