Potassium Phosphate, Tribasic → 5-methyl-1-(4-vinylphenyl)-1H-pyrazole-4-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

Tetrahydrofuran (10 ml) was added to 1-(4-bromophenyl)-5-methyl-1H-pyrazole-4-carboxylic acid ethyl ester (1.5 g) described in Reference Example 26(1), palladium (II) acetate (108 mg), 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (S-Phos) (198 mg), vinylboronic acid pinacol ester (1.04 g) and tripotassium phosphate (2.6 g), and stirred at 100° C. for 7 hours. Water was added to the reaction solution, extracted with ethyl acetate, and the organic layer was washed with water and saturated brine, dried over anhydrous sodium sulfate and concentrated in vacuo. The resulting residue was purified with silica gel column chromatography (n-hexane/ethyl acetate). 4N Aqueous solution of sodium hydroxide (4 ml) and ethanol (10 ml) were added to the purified yellow oily product, stirred at 80° C. for two hours and the reaction solution was washed with ethyl acetate. 1N Hydrochloric acid aqueous solution was added to the aqueous layer at 0° C., and the precipitated solid was washed with diethyl ether and water to give 5-methyl-1-(4-vinylphenyl)-1H-pyrazole-4-carboxylic acid (508 mg).

Provenance & Evidence