COC([C:5]1[N:6]([NH:14][C:15]([NH:17][C:18](=[O:25])C2C=CC=CC=2)=[S:16])[C:7]2[C:12]([CH:13]=1)=[CH:11][CH:10]=[CH:9][CH:8]=2)=O.[OH-].[Na+].O.C(O)(=O)C>>[S:16]=[C:15]1[NH:17][C:18](=[O:25])[C:5]2=[CH:13][C:12]3[C:7]([N:6]2[NH:14]1)=[CH:8][CH:9]=[CH:10][CH:11]=3Into a 1 L beaker, 1-(3-benzoyl-thioureido)-1H-indole-2-carboxylic acid methyl ester (24.27 g, 0.07 mol) and a 2 M solution of sodium hydroxide in water (140 mL, 0.28 mol) were added. The mixture was heated at 85° C. for 75 minutes. The reaction was cooled to room temperature. Acetic acid (16.7 mL, 0.29 mol) was added at 0° C. and the mixture was stirred for 30 minutes. The solid was filtered and dried on filter overnight to afford a white solid, which was further dried under vacuum overnight. NMR indicated about 1:1 molar ratio of product to benzoic acid. Trituration and filtration from hot benzene removed the benzoic acid and afforded 2-thioxo-2,3-dihydro-1H-[1,2,4]triazino[1,6-a]indol-4-one (14.50 g, 96%), which was used in the next step without further purification. 1H-NMR (DMSO-d6) δ 10.29 (br s, 1H), 7.76 (d, J=8.4 Hz, 1H), 7.66 (d, J=8.1 Hz, 1H), 7.3 (br s, 1H), 7.27 (m, 1H), 7.12 (m, 1H), 6.88 (s, 1H).
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