O=[C:2]1[N:7]=[CH:6][C:5]([C:8]2[CH:17]=[CH:16][C:11]([C:12]([O:14][CH3:15])=[O:13])=[CH:10][CH:9]=2)=[N:4][NH:3]1.P(Cl)(Cl)([Cl:20])=O>C(Cl)(Cl)Cl>[Cl:20][C:2]1[N:3]=[N:4][C:5]([C:8]2[CH:17]=[CH:16][C:11]([C:12]([O:14][CH3:15])=[O:13])=[CH:10][CH:9]=2)=[CH:6][N:7]=1A mixture of methyl 4-(3-oxo-2,3-dihydro-1,2,4-triazin-6-yl)benzoate (13.4 g, 0.0580 mol), phosphoryl chloride (30 mL, 0.3 mol) in chloroform (50 mL) was heated at reflux (oil-bath temperature about 100° C.) for 2 h. After cooling, the mixture was concentrated to remove excess phosphoryl chloride. The residue was dissolved in DCM. The solution was poured into ice-water, and carefully neutralized with K2CO3. The organic layer was separated. The aqueous solution was extracted with methylene chloride. The combined extracts were dried over Na2SO3. After filtration the filtrate was concentrated and further purified by flash column to afford the desired product (2.5 g, 17%). Analytical LCMS: (M+H)+=249.9. 1H NMR (300 MHz, CDCl3): 6 (ppm) 3.98 (s, 3H), 8.18 (d, 2H), 8.24 (d, 2H), 8.96 (s, 1H).
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