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26th March 2012 @ 01:10
Product obtained in 74% yield.

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Hydrolysis of pyrazole core ester to the acid in basic conditions.



Reaction Start Time: 11.30 26/03/12
PMY 43-1 (3.46 g, 15.0 mmol, 1 equiv.) was dissolved in EtOH (20 mL). 5M sodium hydroxide (20 mL, 100 mmol, 6.7 equiv.) was added and the mixture heated to reflux. After 165 mins, reaction not complete by TLC. After approx 4 hours, reaction not complete by TLC. After 6 hours, reaction was allowed cooled to room temperature. lab cooling water shutdown Reaction not complete after 16 hours at room temperature. Heated to reflux. After a further 3 hours at reflux, the reaction was cooled in ice, then acidified with 6M HCl (pH 1). The resulting amber precipitate was allowed to ripen for 20 minutes at 0 °C and then filtered and dried under reduced pressured. The amber product was recrystalled from Et2O (approx 50 mL) to obtain the product as colourless plates (1.08 g, 36%). Mpt. (Et2O) 167-168 °C (literature 169 °C doi:10.1002/jhet.5570190620 they ref: 167-168 L. Claisen, Ann. Chem., 295, 1897 301.) The aqueous layer and recrystallisation mother liquours were concentrated under reduced pressure. The resulting residue was refluxed in EtOH then filtered hot. The filtrate was cooled and the precipitate filtered to obtain further product (1.18 g, 39%; 74% total).

TLC (30% EtOAc/hexane) visualised with UV and vanillin:
TLC 4 hours
TLC 165 mins


NMR:
1H NMR


See also:
Synthesis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate (PMY 43-1)

Risk and Hazard Assessment:
As for: Hydrolysis of Ethyl 1-(4-fluorophenyl)-2,5-dimethyl-1H-pyrrole-3-carboxylate (PMY 8-1)

InChi:
Starting materials: InChI=1S/C13H14N2O2/c1-3-17-13(16)12-9-14-15(10(12)2)11-7-5-4-6-8-11/h4-9H,3H2,1-2H3
Product: InChI=1S/C11H10N2O2/c1-8-10(11(14)15)7-12-13(8)9-5-3-2-4-6-9/h2-7H,1H3,(H,14,15)
Linked Posts
Attached Files
Scheme
TLC 165 mins
TLC 4 hours
1H NMR