Sulfuric Acid → 1-(2-Fluoro-4-chloro-5-bromophenyl)-3-methyl-4-(difluoromethyl)-1H-1,2,4-triazol-5(4H)-one

Participants

Reaction Steps

To a 250 mL roundbottom flask equipped with a mechanical stirrer and a thermometer was added 6 mL of 20% fuming sulfuric acid (oleum) (% wt/vol. triazole to solvent—23.3%), 1.4 grams (0.0051 mole—1.0 equiv.) of 1-(4-chloro-2-fluorophenyl)-4-difluoromethyl-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole, and 0.85 gram (0.0053 mole—1.03 equiv.) of bromine crystals. The reaction mixture stirred at ambient temperature for two hours. After this time TLC analysis of the reaction mixture indicated that the reaction was almost complete. The reaction mixture was stirred at ambient temperature for an additional 16 hours. At the conclusion of this period a second TLC analysis of the reaction mixture indicated the reaction was essentially completed. The reaction mixture was poured into 300 grams of ice, and the resulting mixture was extracted with two 50 mL portions of methylene chloride. The organic extracts were combined and washed with an aqueous 10% potassium carbonate solution, an aqueous 5% sodium bisulfite solution, and an aqueous saturated sodium chloride solution. The organic layer was dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure yielding a white solid, which was dried to a constant weight, yielding 1.6 grams of 1-(4-chloro-2-fluoro-5-bromophenyl)-4-difluoromethyl4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole (90.1 % yield) . The NMR spectrum was consistent with the proposed structure.

Provenance & Evidence