Hey all,
I wanted to gather expert input on the stability of dimethylformamide under basic conditions at reflux:
I want to reproduce the results of Michael G. Bell et al. in his patent
"Preparation of 3-phenylisoxazole derivatives for treatment of dyslipidemia
By Bell, Michael Gregory et alFrom PCT Int. Appl., 2007092751, 16 Aug 2007 "
They claim that the condensation reaction of 2-fluorobenzaldehyde with mercaptoacetic acid in refluxing DMF with KOH as base proceeds smoothly and with a yield of 78%.
EDIT: The product of said reaction is benzo[b]thiophene-2-carboxylic acid.
On the other hand it's been reported that KOH as a strong base readily catalyzes the decomposition of DMF to dimethylamine and potassium formate (presumably), as can be read in the EROS article (Chapter e-EROS Encyclopedia of Reagents for Organic Synthesis
).Now I want to ask you guys whether you've worked under these conditions before and whether you've experienced a disastrous decomposition of solvent or a pleasant reaction with pure products :)
Best regards
I deed reaction of benzyl alcohol derivative with 2-fluro toluene using KOH as a base and DMF as a solvent at 80-120°C. Reaction time was 5-12 hr. It was yielding 65-80% desired product. Reaction was almost clean on TLC observed under UV but reaction mass was thickened and darkened with time. What I am assuming is that DMF degradation is happening but with a lower rate than the desired reaction.
Dear Mr. Brown,
the "isoxazole" moiety is of less interest for me, since I strive for the "derivative" part of the invention, i.e. a benzo[b]thiophene moiety :)
The error was on my part as my question might have been stated ambigously. To clear up the question I edited it.
Nonetheless a nice evening to you from my part of the world.
DMF is poorly stable in aqueous alcaline solution. When we deal with concentrated alcali (say KOH over 20%) and temperatures over 50-60 deg, DMF will be completely unstable, it hydrolyses immediately, in seconds (NOTE!).
Meanwhile, this allows to construct very convenient laboratory device for generation of permanently strong stream of dimethylamine gas -
just add dropwise DMF to hot (80-90 deg) stirred solution of about 30-40% KOH, you will get up to 2 moles/hour stream of dimethylamine and this device could work for hours, requiring only minor control.
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