ClC1C=NC=CN=1.NN.[NH:10]([C:12]1[CH:17]=[N:16][CH:15]=[CH:14][N:13]=1)[NH2:11].[F:18][C:19]([F:24])([F:23])[C:20](O)=O.[OH-].[NH4+]>>[NH:10]([C:12]1[CH:17]=[N:16][CH:15]=[CH:14][N:13]=1)[NH2:11].[F:18][C:19]([F:24])([F:23])[C:20]1[N:13]2[CH:14]=[CH:15][N:16]=[CH:17][C:12]2=[N:10][N:11]=1A sample of 2-hydrazinopyrazine was prepared from 2-chloropyrazine and hydrazine using a procedure analogous to that described in the literature [P. J. Nelson and K. T. Potts, J. Org. Chem., 27, 3243 (1962)], except that the crude product was extracted into 10% methanol/dichloromethane and filtered, and the filtrate was concentrated and purified by flash chromatography on silica gel, eluting with 100% ethyl acetate followed by 10% methanol in dichloromethane. A mixture of 2-hydrazinopyrazine (820 mg, 7.45 mmol), trifluoroacetic acid (2.55 g, 22.4 mmol), and polyphosphoric acid (10 mL) was heated to 140° C. with stirring for 18 h. The solution was added to ice and neutralized by the addition of ammonium hydroxide. The aqueous solution was extracted three times with ethyl acetate, washed with brine, and dried over anhydrous magnesium sulfate. Concentration followed by flash chromatography (silica gel, 1:1 hexane:ethyl acetate, then 100% ethyl acetate) afforded the title compound as a solid.
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