Ethanol → [1-(5-Bromo-2-hydroxy-benzyl)-5-methyl-1H-pyrazol-4-yl]-acetic acid ethyl ester

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Reaction Steps

A suspension of N′-(5-bromo-2-hydroxy-benzyl)-hydrazinecarboxylic acid tert-butyl ester 1 1 g (3.1 mmol) in a mixture of CH2Cl2 (8 mL) and TFA (8 mL) was stirred at RT for 2 hours. The volatiles were removed in vacuo. The residue was dissolved in abs. EtOH (7 mL) and added to 3-[1-dimethylamino-methylidene]-4-oxo-pentanoic acid ethyl ester (4.8 mmol) at RT. The resulting mixture was stirred at RT for 1 hour, refluxed for 2 h, let cool down and stirred at RT for 16 h. The oily residue obtained after removing the volatiles in vacuo was purified by MPLC (10 g SiO2 cartridge, eluent 90% iso-hexane-10% EtOAc) to give 0.18 g of [1-(5-Bromo-2-hydroxy-benzyl)-5-methyl-1H-pyrazol-4-yl]-acetic acid ethyl ester, 2.

Provenance & Evidence