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8th October 2012 @ 04:48
Hydrolysis of the pyrazole core ester to carboxylic acid under basic conditions.


Reaction Start Time: 1410, 08-10-2012
MJT2-2 (2.267 g, 9.1 mmol, 1 equiv.), a yellow oil, was dissolved in ethanol (14 mL) and sodium hydroxide (13 mL, 5M, 64 mmol, 7 equiv.) was added. The mixture was heated to reflux at 100 °C. TLC analysis showed reaction completed after 30 minutes. The reaction was left to cool to room temperature and then cooled in ice before HCl (8M) was added until pH1 was reached. The pale yellow solid precipitate was collected by filtration and recrystallised from Et2O (ca. 80 mL) to give MJT3-2 as white needles (1.26 g, 5.7 mmol, 63 %). The aqueous washing was concentrated to give MJT3-2 crude (ca. 400 mg) though this was not used in further reactions.

TLC (30% EtOAc/hexane) visualised with UV and vanillin:
TLC 50 minutes MJT3-2

Hydrolysis of Ethyl 1-(4-fluorophenyl)-5-methyl-1H-pyrazole-4-carboxylate (MJT 3-1). Hydrolysis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate (PMY 44-1)

Risk and Hazard Assessment:
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TLC 50 minutes MJT3-2