To 5-amino-1-methyl-4-(4-methylphenyl)-1H-pyrazol-3-ol (Preparation 3a) (5 g) in dimethylformamide (30 ml) at room temperature was added potassium carbonate (24.8 g) and 4-fluorophenoxyethylbromide (5.6 g), the mixture was stirred for 16 hrs. The reaction was partitioned between water (100 ml) and diethyl ether (100 ml). The aqueous layer was separated and extracted with further diethyl ether (4×100 ml). The organic fractions were combined, washed with water, then brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure azeotroping with xylene. The residue was purified by column chromatography on silica gel eluting with a solvent gradient, pentane:ethylacetate (7:3 to 0:1, by volume) to yield the title compound as a white solid (4.95 g).
