[NH2:1][C:2]1[C:7](Cl)=[N:6][CH:5]=[CH:4][N:3]=1.O(CC)[C:10]([S-:12])=[S:11].[K+].CN1CCCC1=O.C(O)(=O)C>O>[S:12]1[C:7]2[C:2](=[N:3][CH:4]=[CH:5][N:6]=2)[NH:1][C:10]1=[S:11]To a mixture of 2-amino-3-chloropyrazine (5.0 g, 38.6 mmol) and potassium ethyl xanthate (9.28 g, 57.9 mmol) was added 1-methyl-2-pyrrolidinone (68 mL). The solution was stirred and heated at 150° C. for 16 h. After cooling to rt, glacial acetic acid (10 mL) and water (1500 mL) were added to the solution. The solid precipitate was filtered. The solid was suspended in 1:1 EtOH/water (500 mL) and sonicated. The solid was once again filtered, washed with water, and dried with CaSO4 in vacuo for 16 h to yield the product (4.36 g, 67%). 1H NMR (500 MHz, DMSO-d6): 14.69 (br s, 1H), 8.42 (d, J=2.8, 1H), 8.39 (d, J=2.8, 1H). MS (ESI): mass calcd. for C5H3N3S2, 168.98; m/z found, 170.00 [M+H]+.
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