General procedure for the synthesis of 5-aminothiazole hydrochloride from tert-butyl thiazole-5-carbamate: To a stirred solution of tert-butyl thiazole-5-carbamate (379, 300 mg, 1.5 mmol) in methanol (5 mL), protected by argon at 0°C, a 1,4-dioxane solution (5 mL) in 4N HCl was slowly added. The reaction mixture was gradually warmed up to room temperature and stirring was continued for 3 hours. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the volatile solvent was removed under reduced pressure to give the crude product. The crude product was washed with n-pentane (2 × 5 mL) and subsequently dried under reduced pressure to afford 5-aminothiazole hydrochloride (380, 150 mg, HCl salt) as a light yellow solid.TLC conditions: 50% ethyl acetate/hexane (Rf 0.1); 1H-NMR (DMSO-d6, 500 MHz) data: δ 9.10 (s, 1H), 7.22 (s. 1H).
