Boron tribromide → 1-(4-chloro-2-fluoro-5-hydroxyphenyl)-3-difluoromethyl-4,5-dihydro-4-methyl-1,2,4-triazol-5(1H)-one

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Reaction Steps

To a stirred ice cold solution of 1.5 g (0.0048 mole) of 1-(4-chloro-2-fluoro-5-methoxyphenyl)-3-difluoromethyl-4,5-dihydro-4-methyl-1,2,4-triazol-5(1H)-one in 80 mL of methylene chloride was added dropwise 14.2 mL of a 1M solution of boron tribromide in methylene chloride. After complete addition the mixture was allowed to warm to room temperature and stir for approximately 18 hours. The mixture was poured into ice water and the resultant mixture stirred until the ice had melted. The organic phase was separated from the mixture and was washed with two portions of water. After washing, the organic phase was dried over anhydrous magnesium sulfate and filtered. Evaporation of the filtrate under reduced pressure yielded 1.2 g of 1-(4-chloro-2-fluoro-5-hydroxyphenyl)-3-difluoromethyl-4,5-dihydro-4-methyl-1,2,4-triazol-5(1H)-one (mp 153°-155° C.), Compound 23.

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