[NH2:1][C:2]1[N:3]=[C:4]([S:9][CH3:10])[S:5][C:6]=1[C:7]#[N:8].S(=O)(=O)(O)O.[OH2:16].[CH:17](O)=O>>[CH3:10][S:9][C:4]1[S:5][C:6]2[C:7](=[O:16])[NH:8][CH:17]=[N:1][C:2]=2[N:3]=1To a solution of 4-amino-2-(methylthio)thiazole-5-carbonitrile (800 mg) in formic acid (8 mL) was added concentrated sulfuric acid (3.2 mL) dropwise for 15 min. The reaction mixture was stirred at 90-100° C. for 1 h and allowed to rt. The reaction mixture was poured into ice cooled water and stirred for 15 min. The precipitated solid was filtered, washed with water and dried to give the product as a white color solid (820 mg, 88%), mp 260-262° C. 1H NMR (400 MHz, DMSO-d6): δ 12.83 (1H, br s), 8.25 (1H, s), 2.80 (3H, s); LC-MS (negative ion mode): m/z 198 (M−H)−.
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