10.0 g (44.1 mmol) of 4,5-dibromo-2H-1,2,3-triazole (commercially available) was dissolved in 90 mL of tetrahydrofuran, 6.1 g (44.2 mmol) of potassium carbonate was added as a base, and the reaction mixture was cooled to -10 °C. Subsequently, 7.5 g (53 mmol) of iodomethane was slowly added. The reaction system was warmed to 35-40 °C with continuous stirring until the reaction was complete. Upon completion of the reaction, the reaction was quenched by the addition of 50 mL of water and the tetrahydrofuran (~90 mL) was removed by distillation. Extraction was carried out with methyl tert-butyl ether and the organic phase was dried with anhydrous magnesium sulfate. Concentrated to dryness under reduced pressure, 10 mL of methyl tert-butyl ether was added to the residual solid, and 70 mL of hexane was added slowly and dropwise to induce precipitation of the solid. After addition, stirring was continued for 1 to 2 hours at room temperature. The solid was collected by filtration to give 5.8 g of pure 4,5-dibromo-1-methyl-1H-1,2,3-triazole in 57% yield.
