Sulfuric Acid → 1-[4-chloro-2-fluoro-5-(4-hydroxyphenoxy)phenyl]-4-difluoromethyl-4,5-dihydro-3-methyl-1,2,4-triazol-5(1H)-one

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Reaction Conditions

Reaction Steps

While maintaining a temperature of 20° to 25° C., 4.4 g (0.011 mole) of 1-[5-(4-aminophenoxy)-4-chloro-2-fluorophenyl]-4-difluoromethyl-4,5-dihydro -3-methyl-1,2,4-triazol-5(1H)-one was added to 4.0 mL of stirred, concentrated sulfuric acid. To this was added a solution of 0.89 g (0.13 mole) of sodium nitrite dissolved in 6.0 mL of water, while continuing to maintain a temperature of about 20° C. After complete addition, the mixture was stirred at 20° C. for 30 minutes. This mixture was added through a glass tube to the bottom of a stirred, refluxing mixture of 32.0 g (0.13 mole) of copper (II) sulfate pentahydrate, 80 mL of water and 30 mL of xylene. After complete addition the mixture was refluxed for one hour. The mixture was cooled, and the organic phase was separated from the aqueous phase. The organic phase was extracted with an aqueous, sodium hydroxide solution (6.0 g of sodium hydroxide pellets dissolved in 250 mL of water). The basic extract was neutralized with concentrated hydrochloric acid, causing a precipitate to form. The solid was collected by filtration to yield 2.3 g of 1-[4-chloro-2-fluoro-5-(4-hydroxyphenoxy)phenyl]-4-difluoromethyl-4,5-dihydro-3-methyl-1,2,4-triazol-5-(1H)-one, m.p. 162°-162° C., Compound 2 of Table 1.

Provenance & Evidence