[NH:1]([C:3]1[CH:8]=[N:7][CH:6]=[CH:5][N:4]=1)[NH2:2].ClC1C=NC=CN=1.NN.[C:18](O)([C:20]([F:23])([F:22])[F:21])=O.[OH-].[NH4+]>>[F:21][C:20]([F:23])([F:22])[C:18]1[N:4]2[CH:5]=[CH:6][N:7]=[CH:8][C:3]2=[N:1][N:2]=1A mixture of 2-hydrazinopyrazine (820 mg, 7.45 mmol), 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. 1962, 27, 3243, 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), TFA (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 with ethyl acetate (3×), 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 (861 mg). 1H NMR (500 MHz, CDCl3) δ 8.17˜8.20 (m, 2H), 9.54 (s, 1H). LC/MS (M+1) 189.
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