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4th October 2012 @ 07:36
Synthesis of ethyl 5-methyl-1-phenyl-1H-pyrazole-4-carboxylate from ethylacetoacetate, dimethylformamidedimethylacetal and phenylhydrazine.

5-methylpyrazoleester.png


Reaction Time: 24-08-2012 (10.55 IST)

Experimental Procedure: Dimethylformamidedimethylacetal (2.7 mL, 1 equiv, 28 mmol) was added with stirring to ethylacetoacetate (4.5 mL, 1.21 equiv, 34 mmol), the mixture turned yellow then it was heated to reflux for 2 hours at 100 oC. TLC showed consumption of ethylacetoacetate. The generated enamineketone was taken up in ethanol (60 mL) and phenylhydrazine (4.3 mL, 1.21 equiv, 34 mmol) was added to it. The reaction mixture was heated at 80 oC (reflux). After 1 hour TLC showed consumption of phenylhydrazine. The reaction mixture was evaporated under vacuum and to it was added water (50 mL) followed by extraction with EtOAc (3 X 30 mL). The organic layers were combined and washed with brine (40 mL), dried with anhydrous Na2SO4 and concentrated under reduced pressure to afford the crude product which was purified by column chromatography (EtOAc/hexanes, 10:90, v/v) to obtain the product as yellowish oil (5.41, 84 %).


TLC after 2 hour (20% ethyl acetate in hexane) visualised using UV and I2:
2012-08-24 19.17.12.jpg


TLC after 3 hour (20% ethyl acetate in hexane) visualised using UV and I2:
2012-08-24 19.44.40.jpg


1 NMR Spectra:
SBHK-486-H1.JPG
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2012-08-24 19.17.12.jpg
2012-08-24 19.44.40.jpg
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Comments
Re: Synthesis of ethyl 3-methyl-1-phenyl-1H-pyrazole-4-carboxylate (SBHK-486) by Paul Ylioja
17th October 2012 @ 06:46
I'm just wondering if that is the correct product from the reaction? Your NMR spectra matches mine for the same reaction (http://malaria.ourexperiment.org/uri/c0) conditions and the literature NMR for the 5-methyl isomer (http://dx.doi.org/10.1016/j.jfluchem.2011.07.014). I haven't done any 2D NMR on the pyrazole so I can't be certain.
Re: Synthesis of ethyl 3-methyl-1-phenyl-1H-pyrazole-4-carboxylate (SBHK-486) by B.Harikrishna
18th October 2012 @ 06:59
After cheking NMR and literature, i realised that what i am getting is not 3-methyl isomer(thanks for ur comment). i will be correcting it to 5-methyl isomer in my blog soon.