O[C:2]1[C:3]2[N:4]([C:12]([C:15]([F:18])([F:17])[F:16])=[N:13][N:14]=2)[C:5]2[C:10]([N:11]=1)=[CH:9][CH:8]=[CH:7][CH:6]=2.P(Cl)(Cl)([Cl:21])=O.C(N(CC)CC)C>C(Cl)(Cl)Cl>[Cl:21][C:2]1[C:3]2[N:4]([C:12]([C:15]([F:18])([F:17])[F:16])=[N:13][N:14]=2)[C:5]2[C:10]([N:11]=1)=[CH:9][CH:8]=[CH:7][CH:6]=2In a flame-dried reaction flask under a dry nitrogen atmosphere, there were placed 3.0 g. (0.0118 mole) of 4-hydroxy-1-trifluoromethyl-[1,2,4]triazolo[4,3-a]quinoxaline and 30 ml. of phosphorus oxychloride in 2.38 g. (0.0236 mole) of triethylamine (3.3 ml.). The reaction mixture was then heated at 100° C. for a period of approximately 16 hours (i.e., overnight). Upon completion of this step, the spent mixture was cooled to room temperature, concentrated in vacuo and then partitioned between ice, water and ethanol, followed by extraction with ethyl acetate. The latter extract was next washed with saturated brine and dried over anhydrous magnesium sulfate. After removal of the drying agent by means of filtration and the solvent by means of evaporation under reduced pressure, there was obtained a residue which was subsequently dissolved in hot chloroform and filtered. The latter filtrate was then allowed to stand overnight at room temperature and filtered again. The final filtrate was then concentrated in vacuo to ultimately afford 1.4 g. of 4-chloro-1-trifluoromethyl[1,2,4] triazolo[4,3-a]quinoxaline in the form of a brownish-colored solid.
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