Hydrogen Bromide → 2-Bromo-5-(trifluoromethyl)-1,3,4-thiadiazole

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A solution of 69 g (1.0 mole) of sodium nitrite in 150 ml of water was added dropwise over the course of 1.5 hours, while stirring, to a solution, cooled to +5° C, of 84.5 g (0.5 mole) of 2-amino-5-trifluoromethyl-1,3,4-thiadiazole in a mixture of 400 ml of hydrogen bromide (48% strength) and 100 ml of water. Thereafter, the evolution of the nitrous gases and of the nitrogen was completed by stirring at 25° C (1 hour). The product separated out as a dark brown, heavy liquid and was abstracted from the reaction mixture by repeated extraction with a total of 500 ml of methylene chloride. After washing with 2 × 100 ml of water, drying over sodium sulfate and careful distillation of the solvent, the residue was fractionated in vacuo through a short column. 101 g (87% of theory) of 2-bromo-5-trifluoromethyl-1,3,4-thiadiazole of boiling point 55° C/10 mm Hg were obtained. ##STR80##

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