Author Topic: Vanillin Demethylation with Pyridine and AlCl31  (Read 2386 times)

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9873468096

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Vanillin Demethylation with Pyridine and AlCl31
« on: April 01, 2004, 07:06:00 PM »
When doing a vanillin demethylation, what other chemicals can one substitute the Pyridine, triethylamine? Can I use aniline?

I understand microwaving is the way to go on demethylation.

Can one microwave the following methylation with DCM+base, or will MW* have a disruptive effect on the methylation like it does on the Vilsmeier?

https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html#pyralcl3



Anhydrous AlCl3 (9.7 g, 0.0724 mol) was suspended in a solution of 10g (0.0658 mol) of vanillin in 100 ml of methylene chloride in an apparatus protected from atmospheric moisture. While stirring briskly and cooling to maintain the temperature at 30-35°C, 22.9g (0.290 mol) of pyridine was added slowly. The reaction was vigorous; the resulting clear light orange solution of the reaction complex was heated to reflux (45°C) and maintained at that temperature with stirring for 24 hours. The solution, which had darkened only slightly during the reflux period, was cooled to 25°C and the product was hydrolyzed, while stirring and maintaining the temperature at 25-30°C, by the addition of dilute (15-20%) HCl until the mixture was definitely acidic to congo red indicator. Of the two phases present at this time, the lower methylene chloride layer contained most of the small amount of the unchanged vanillin, and essentially no protocatechuic acid, the latter was dissolved in the aqueous phase. Evaporation of the methylene chloride yielded 0.8 g of vanillin. Extraction of the aqueous phase with ether followed by evaporation of the ether left 7.9 g (87%) of pale yellow crystals of protocatechualdehyde melting at 153-154°C.

Using the cheaper triethylamine in place of pyridine lowered the yield to 61.5%

BieneMaya

  • Guest
I don´t know if it works with vanilin but the...
« Reply #1 on: April 01, 2004, 07:17:00 PM »
I don´t know if it works with vanilin
but the demethylation fo opiates can be done
with HBr, HF as well as with BBr3 and BCl3.

Of course BBr3 and BCl3 is harder to get.

Maybe some other more experienced bee can help
but my clue could be a good idea for further research.

Rhodium

  • Guest
Pyr*HCl
« Reply #2 on: April 01, 2004, 08:04:00 PM »
You have this pyridine hydrochloride procedure:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html#pyrhcl



It is exemplified for eugenol, but I assume you can see the obvious similarities to vanillin.


9873468096

  • Guest
Vanillin Demethylation with Pyridine and AlCl31
« Reply #3 on: April 01, 2004, 09:19:00 PM »
I don´t know if it works with vanilin
but the demethylation fo opiates can be done
with HBr, HF as well as with BBr3 and BCl3.

Thank you for the thought, but I am trying to figure out what other amines I can use instead of pyridine.

Anybody?

Rhodium

  • Guest
triethylamine is the only other reasonable option
« Reply #4 on: April 01, 2004, 09:23:00 PM »
I'd say that triethylamine is the only other reasonable option, and that you are guaranteed a lower yield using that. How much lower is unknown until you have tried.


9873468096

  • Guest
Methylation with DCM and Base
« Reply #5 on: April 02, 2004, 06:47:00 PM »
Can one microwave the following methylation of protocatechualdehyde with DCM + base without disruptive effects?

Rhodium

  • Guest
I'd say the DCM would evaporate too fast for...
« Reply #6 on: April 02, 2004, 08:26:00 PM »
I'd say the DCM would evaporate too fast for such a trial to be useful.


9873468096

  • Guest
Knoevenagel vs Methylation
« Reply #7 on: April 02, 2004, 10:33:00 PM »
A lot of bees have been talking about great results after leaving the Knoevenagel with Piperonal + Nitroethane + Amine of choice sitting for 3 weeks or so. Claiming almost perfect yields.

How about applying that strategy to methylation of protocatechualdehyde with DCM + Base? Just mix together and let is sit for like 3 weeks. Better idea than MW*?

Rhodium

  • Guest
very different
« Reply #8 on: April 03, 2004, 01:06:00 AM »
Those reactions are unrelated, so you cannot generalize like that.

I suggest you UTFSE for "methylenation" to see what procedures has been published and shown to work, before you start to throw around wild guesses.