[CH3:1][S:2][C:3]1[N:8]=[C:7]([CH:9]([CH:12]=O)[C:10]#[N:11])[CH:6]=[CH:5][N:4]=1.[NH2:14][NH2:15].O.Cl>C(O)C>[CH3:1][S:2][C:3]1[N:8]=[C:7]([C:9]2[CH:12]=[N:14][NH:15][C:10]=2[NH2:11])[CH:6]=[CH:5][N:4]=1A suspension of 2-(2-(methylthio)pyrimidin-4-yl)-3-oxopropanenitrile (5) (100 g, 0.52 mol), NH2NH2—H2O (85%, 31.2 g, 0.62 mol) and conc. HCl (60 mL) in ethanol (1 L) was stirred at reflux for 5 h. After cooled to room temperature, the mixture was concentrated in vacuum, and the residue was washed with ether (200 mL×3) and suspended in H2O (200 mL). The mixture was basified with saturated aq. Na2CO3 to pH 9 and the precipitate was collected. The solid was washed with H2O (100 mL×3) and ether (200 mL×3), then dried in vacuum to give 4-(2-(methylthio)pyrimidin-4-yl)-1H-pyrazol-5-amine (6) (56.8 g, 51.8%) as a yellow solid. 1H NMR (400 MHz, CD3CN): δ 8.295 (d, 1H), 7.826 (s, 1H), 7.101 (d, 2H), 5.800 (d, 1H), 2.586 (s, 3H).
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