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Ethylbromopyruvate (7.1 mL, 56.8 mmol) was added to a slurry of ammonium dithiocarbamate (6.25 g, 56.8 mmol) in EtOH (35 mL). The solution was stirred at rt 18 h, then heated at 70°-80° C. for 2 h. The solution was cooled to 10° C. and water (70 mL) was added. The resulting precipitate was recrystallized from EtOH to give 0.7 g of 4-carboethoxy-2-mercapto thiazole. NCS (0.42 g, 3.17 mmol) was added to a solution of 4-carboethoxy-2-mercapto thiazole (0.15 g, 0.79 mmol) in CH2Cl2 (3.2 mL) and the solution layered with water (1.6 mL) and stirred for 2 h. The layers were separated and the water layer extracted with CH2Cl2. The combined extracts were concentrated and the residue dissolved in acetone (1 mL) and NH4OH (1.6 mL) added. After 5 min the acetone was removed in vacuo and the residue taken up in water and extracted with EtOAc (6×5 mL). The combined extracts were dried (MgSO4), filtered, concentrated and purified by chromatography using 35% EtOAc/hexane to give 0.1 g (54%) 4-carboethoxy-2-thiazole sulfonamide as a pale yellow solid.

1. temperatureheated at 70°-80° C. for 2 h
2. temperatureThe solution was cooled to 10° C.
3. customThe resulting precipitate was recrystallized from EtOH