[C:1]([C:4]1[CH:9]=[CH:8][C:7]([NH:10][C:11]([NH:13][NH:14][C:15]([O:17]CC)=O)=[O:12])=[CH:6][CH:5]=1)(=[O:3])[CH3:2].C([O-])([O-])=O.[K+].[K+].Cl.O1CCOCC1>CO>[C:1]([C:4]1[CH:5]=[CH:6][C:7]([N:10]2[C:11](=[O:12])[NH:13][NH:14][C:15]2=[O:17])=[CH:8][CH:9]=1)(=[O:3])[CH3:2]To ethyl 2-(4-acetylphenylcarbamoyl)hydrazinecarboxylate (I-4a: 354 mg, 1.335 mmol) in MeOH (10 mL) was added K2CO3 (553 mg, 4.00 mmol). The mixture was stirred at 55° C. for 2 hours, cooled to room temperature, and then HCl 4N in dioxane (1.668 mL, 6.67 mmol) was added. The precipitate was filtered, and the filtrate was concentrated in vacuo. The resulting solid was triturated in CH2Cl2, filtered and dried giving 4-(4-acetylphenyl)-1,2,4-triazolidine-3,5-dione (I-4b: 125 mg, 43%) as a light yellow solid. LC-MS (M+1) 220.2, t=0.78 minute. 1H NMR (400 MHz, DMSO-d6) δ ppm 2.60 (s, 3 H) 7.68 (d, J=8.84 Hz, 2 H) 8.05 (d, J=8.59 Hz, 2 H) 10.65 (s, 2 H).
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