Ethanol → 1-(5-Bromo-2-hydroxy-benzyl)-5-methyl-1H-pyrazole-4-carboxylic acid methyl ester

Participants

Reaction Steps

A suspension of N′-(5-bromo-2-hydroxy-benzyl)-hydrazinecarboxylic acid tert-butyl ester 1 2 g (6.3 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 2-[1-Dimethylamino-meth-(Z)-ylidene]-3-oxo-butyric acid methyl ester (12 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 0.38 g of 1-(5-Bromo-2-hydroxy-benzyl)-5-methyl-1H-pyrazole-4-carboxylic acid methyl ester, 5 and 1-(5-Bromo-2-hydroxy-benzyl)-3-methyl-1H-pyrazole-4-carboxylic acid methyl ester 6 as a mixture.

Provenance & Evidence