Sulfuric Acid → ethyl 5-[3-(trifluoromethoxy)phenoxy]-2-[4-(trifluoromethyl)phenyl]-2H-1,2,3-triazole-4-carboxylate

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To a solution of ethyl 2-[2-amino-4-(trifluoromethyl)phenyl]-5-[3-(trifluoromethoxy)phenoxy]-2H-1,2,3-triazole-4-carboxylate (i.e. the product of Step G, 0.70 g, 1.5 mmol) in ethanol (20 mL) was added concentrated sulfuric acid (2 mL). The stirring mixture was cooled to −20° C., and then isopentyl nitrite (0.91 g, 8.8 mmol) was added dropwise over 5 min. The reaction mixture was stirred at −20° C. for 1 h, after which an aqueous solution of hypophosphorus acid (3.9 g, 29.4 mmol, 50% in water) was added. The solution was stirred at 23° C. for 14 h. The reaction mixture was diluted with saturated aqueous sodium chloride solution (20 mL), extracted with ethyl acetate (2×40 mL), and washed with saturated aqueous sodium bicarbonate solution (2×20 mL). The organic layer was dried (MgSO4) and concentrated under reduced pressure to afford the crude residue which was purified by chromatography on silica gel eluting with 0 to 15% ethyl acetate in hexanes to obtain the title compound (0.55 g) as a colorless solid.

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