Potassium Hydroxide → 5-(2,4-Bis-benzyloxy-phenyl)-1H-pyrazole-3-carboxylic acid

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Reaction Steps

A solution of ethyl 3-(2,4-dibenzyloxyphenyl)-pyrazole-5-carboxylate (1.5 g) in methanol (20 mL) and THF(10 mL) is treated with aqueous 10% KOH (7.5 mL) and refluxed for 2 hours. The solution is evaporated, brought to pH 1 with 1 M HCl, and the precipitate filtered. The solid is purified by flash chromatography on silica, eluting with dichloromethane/methanol (98:2). Fractions homogeneous in the required product are combined and evaporated. The residue is recrystallized from ethyl acetate to give 3-(2,4-dibenzyloxyphenyl)-pyrazole-5-carboxylic acid as colourless crystals (0.13 g), m.p. 218-219° C. 1H NMR (CDCl3) 5.1 (2H,s), 5.2(2H,s), 6.68(1H,d), 6.72(1H,s), 7.3-7.5(11H,m), 7.7(1H,d).

Provenance & Evidence