Bromine → 2-Amino-5-methyl-4,5,6-trihydrobenzothiazol-7-one

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Reaction Steps

5-Methyl-cyclohexane-1,3-dione (70.0 g, 0.555 mol) and NaOAc (68.3 g, 0.832 mol) are suspended in AcOH (700 mL) and Br2 (88.7 g, 0.555 mol) is added drop-wise while maintaining the reaction temperature between 15 and 20° C. After complete addition, the reaction is stirred at RT overnight. Thiourea (42.2 g, 0.555 mol) is added in portions and the reaction mixture is heated to 100° C. for 1 h. After cooling to RT, the AcOH is removed in vacuo. The resulting crude product is diluted with water (1 L), adjusted to pH=7 with NaHCO3 solution (3 M) and the resulting mixture is extracted with EtOAc (3×1 L). The organic phase is washed with brine and dried over anhydrous Na2SO4. The solvent is evaporated in vacuo and the residue is recrystallized from hexane to give 2-amino-5-methyl-5,6-dihydro-4H-benzothiazol-7-one (87.2 g, 86% yield).

Provenance & Evidence