Thionyl Chloride → 4-Bromothiazole-2-carbohydrazide

To a solution of 4-bromothiazole-2-carboxylic acid (2.0 g, 9.8 mmol) in methanol (10 mL) was added thionyl chloride (710 μL, 9.8 mmol) and the mixture was refluxed for 3 hours. The solvent was removed under reduced pressure, and the residue was suspended in ethanol (10 mL). To this suspension was added hydrazine hydrate (2.4 mL, 49 mmol), and the reaction was heated to reflux for 90 minutes. The solvent was removed under reduced pressure, and the residue suspended in acetonitrile, filtered, and the solids were washed with acetonitrile, diethyl ether, and dried under vacuum to afford 1.7 g (77%) of 4-bromothiazole-2-carbohydrazide as a yellow solid. M+1=222.1