All Notebooks | Help | Support | About
11th September 2012 @ 06:10
Hydrolysis of the pyrazole core ester to carboxylic acid under basic conditions.

3124.png

Reaction Start Time: 18.45 11/09/12
MJT 2-1 (0.842 g, 3.4 mmol, 1 equiv.), an orange oil, was dissolved in ethanol (4.5 mL) and sodium hydroxide (4.8 mL, 5M, 24 mmol, 7 equiv.) was added, the reaction mixture was left stirring over night at room temperature. After 14 hours stirring at room temperature TLC showed no reaction. 915am The mixture was set to reflux at 100˚C, after 1 hour TLC showed product formation and consumption of starting material. The reaction (yellow mixture) was left to cool at room temperature for 1 hour then cooled in ice and acidified with 6M HCl (pH1). The cream precipitate was then isolated and dried by filtration under reduced pressure. This crude solid (1.442 g) was recrystallised from diethyl ether (15 mL), some (estimate: a third) was lost due to bumping.
First crop gave the carboxylic acid (0.160 g, 0.73 mmol, 22%) as white needles which will be used for characterisation.
TLC showed that the aqueous run off contained no product.
The solvent was removed from the mother liquor and recrystallised from ether again. Not much solid precipitated out so solvent was removed and the solid recrystallised from the minimum amount of ethanol (~2 mL) to give a second crop of cream coloured powder (144 mg, 0.66 mmol, a further 20% making 42% in total).
A melting point of the pure sample gave 168-169 ˚C.

TLC (30% EtOAc/hexane) visualised with UV and vanillin:
TLC after 10 minutes of reflux
TLC after 1 hour of reflux
TLC 3-1 showing no product in aq layer
TLC of first crop of (pure) 3-1 showing it contains no starting material


IR:
IR 3-1


Reference
Hydrolysis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate (PMY 44-1)

Risk and Hazard Assessment:
HIRAC MJT 3-1
Linked Posts
Attached Files
HIRAC MJT 3-1
Scheme MJT 3-1
TLC after 10 minutes of reflux
TLC after 1 hour of reflux
TLC 3-1 showing no product in aq layer
TLC of first crop of (pure) 3-1 showing it contains no starting material
IR 3-1