General procedure for the synthesis of 4-bromo-1-methyl-1,2,3-triazole from 4,5-dibromo-1-methyl-1,2,3-triazole: 2.0 g (8.30 mmol) of 1-methyl-4,5-dibromo-1H-1,2,3-triazole was dissolved in 15 mL of tetrahydrofuran and cooled to -10°C. 4.77 mL (9.55 mmol) of 2.0 M isopropylmagnesium chloride/tetrahydrofuran solution (commercially available, concentration 2.0 M). Upon completion of the reaction, the reaction was quenched by the addition of 15 mL of hydrochloric acid. The reaction mixture was extracted with 20 mL of methyl tert-butyl ether, the organic phases were combined and dried over anhydrous magnesium sulfate. The organic phase was concentrated under reduced pressure to about 5 mL and cooled to 0-5°C to crystallize. The crystals were collected by filtration and dried under vacuum at 40°C to give 1.55 g of 4-bromo-1-methyl-1H-1,2,3-triazole in 90% yield.
