[S:1]1[C:13]2[C:12]3[CH:11]=[CH:10][CH:9]=[CH:8][C:7]=3[N:6]=[CH:5][C:4]=2[N:3]=[C:2]1S.[OH-].[Na+].OO>O.[OH-].[Na+]>[S:1]1[C:13]2[C:12]3[CH:11]=[CH:10][CH:9]=[CH:8][C:7]=3[N:6]=[CH:5][C:4]=2[N:3]=[CH:2]1Thiazolo[4,5-c]quinoline-2-thiol (8.7 g, 0.04 mole) was suspended in a solution of sodium hydroxide (1.4 g, 0.04 mole) in water. A few drops of 50% sodium hydroxide were added to the suspension until most of the solid dissolved. Hydrogen peroxide (13.5 mL of 30%, 0.08 mole) was added dropwise over a period of 30 minutes while maintaining the temperature of the reaction mixture at 25-35° C. with a cold water bath. The bath was removed and the reaction mixture was stirred for 15 minutes. Sulfuric acid (2.5 g of 95.98%) was added dropwise to the reaction mixture. After 30 minutes the reaction was made basic (pH 9-9.5) with 50% sodium hydroxide. The reaction mixture was acidified (pH 2.5) with hydrochloric acid, a tan solid precipitated. The mixture was then heated on a steam bath for 15 minutes and the precipitate dissolved. The solution was allowed to cool to ambient temperature and a precipitate formed. The mixture was made basic (pH 9) with 50% sodium hydroxide. The resulting oily product was extracted with ethyl acetate. The extracts were combined, washed with water, dried over magnesium sulfate and then concentrated under vacuum to provide 3.3 g of thiazolo[4,5-c]quinoline as a tan solid, m.p. 104.4-105° C. Analysis: Calculated for C10H6N2S: %C, 64.19; %H, 3.25; %N, 15.04; Found: %C, 64.15; %H, 3.26; %N, 14.9.
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