p-Toluenesulfonic acid → 4-Acetyl-5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)pyrazole

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Reaction Steps

To a solution of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-ethynylpyrazole (0.318 g) in acetonitrile (10 ml) was added p-toluenesulphonic acid (0.455 g) and the mixture was stirred at room temperature for 1.5 hours and then evaporated to dryness. The residue was taken up in ether and washed with saturated aqueous sodium hydrogen carbonate solution (5 ml). The aqueous layer was twice extracted with ether. The combined organic layers were dried (Na2SO4) and evaporated. The residue was purified by column chromatography on silica gel eluted with hexane:ether (1:1). Combination and evaporation of suitable fractions gave a yellow solid which was further purified by reverse phase high performance chromatography on C18 silica eluted with acetonitrile:water:methanol (60:30:10). Appropriate fractions were combined and evaporated to give, after recrystallisation from propan-2-ol, the title compound as a white solid, m.p. 192.3-192.7° C.

Provenance & Evidence