Trifluoroacetic acid → (1-(4-[(7-Chloro-3-methylbenzofuran-2-carbonyl)amino]benzyl)-3,5-dimethyl-1H-pyrazol-4-yl)acetic acid

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Reaction Steps

To a solution of 7-chloro-3-methylbenzofuran-2-carboxylic acid (185 mg, 0.88 mmol) in 6 mL dichloromethane is added oxalyl chloride (0.123 mL, 1.14 mmol) and a drop of dimethylformamide. After stirring at room temperature for 1 hour the solvent is removed by evaporation in vacuo. The residue is dissolved in dichloromethane (5 mL) and dropped to a solution of [1-(4-aminobenzyl)-3,5-dimethyl-1H-pyrazol-4-yl]acetic acid tert-butyl ester (428 mg, 1 mmol) in form of the toluene sulfonate salt and diisopropylethylamine (0.39 mL, 2.27 mmol) in dichloromethane (5 mL). After addition of 4-dimethylaminopyridine (11 mg, 0.09 mmol) the solution is stirred at room temperature for 12 hours. The solution is extracted twice with hydrochloric acid (1 M), twice with water, twice with an aqueous solution of NaOH (1 M) and twice with water. The organic layer is dried over MgSO4, filtered and the solvent is evaporated in vacuo to yield 426 mg of (1-(4-[(7-chloro-3-methyl-benzofuran-2-carbonyl)amino]benzyl)-3,5-dimethyl-1H-pyrazol-4-yl)acetic acid tert-butyl ester (ESI mass spectrum: [M+H]+=508; Retention time HPLC: 1.60 min (method H)). b) To a solution of (1-(4-[(7-chloro-3-methyl-benzofuran-2-carbonyl)amino]benzyl)-3,5-dimethyl-1H-pyrazol-4-yl)acetic acid tert-butyl ester (426 mg, 0.84 mmol) in dichloromethane (10 mL) is added trifluoroacetic acid (400 mL, 5.2 mmol) and the mixture is stirred at room temperature for 3 days. The solvent is evaporated in vacuo, and the residue is suspended in water and treated with diethyl ether and the precipitating product is filtered off to yield 174 mg of the title compound (ESI mass spectrum: [M+H]+=452; Retention time HPLC: 1.39 min (method J)).

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