Rhodium (Chief Bee)
07-20-01 19:43
No 192174
      High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

I have found a synthesis with an apparently high yield of 3,4,5-trimethoxybenzaldehyde (with 5-bromovanillin as intermediate) from vanillin. It is in russian, but I hope Antoncho can help us with the translation. The information on vanillin dimerization is uninteresting, but all the preparation details from vanillin to 3,4,5-trimethoxybenzaldehyde is desired. If possible, I'd like to know the rationale behind the addition of a Cu2+ salt (usually a Cu(I) salt is used), and if there is any point in making iodovanillin as they describe, and how that is done.

The PDF file of the article can be found here: ../rhodium/bromovanillin.pdf

The Hive - Clandestine Chemists Without Borders
(Stranger / Eraser)
07-21-01 18:15
No 197898
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Hello Rhodium,
this Russian paper describes separation of vanillin and syringaldehyde from their mixture. The authors state that the separation is very hard and they suggest to make less soluble derivative of vanilline first and then separate the mixture. The authors showed that dimerization and bromination of vanillin affords good results. The scheme, which describes synthesis of trimethoxybenzaldehyde from vanillin, is there only for illustration of use of prepared bromovanillin. I think the only valuable information from this paper is citations #10 and #11 and maybe details of bromination of vanillin.
(Official Hive Translator)
07-22-01 12:01
No 198026
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Yes, i'm afraid this article isn't much of a news, but still has a couple of new tidbits of information. It's another purification procedure of syringaldehyde(SA) from vanillin. The first suggested route is via dimerization of vanillin and the second one is through bromination of its mxtr w/SA. The article says that "we found the optimal amount of Br2 used to be 1,2 mole per 1 mole of vanillin....with yields of bromoV 92-95%... The reaction is most conveniently carried out in a 3-component mxtr of aqua/alcohol or aqua/acetic acid with up to 10% polyatomic alc. (glycerin, ethyleneglycol, diethyleneglycol, propyleneglycol) added, under which cond's the resulting bromovanillin precipitates and SA stays in the soln." The SA is then precip'd in cold water, dissolved  in AcOH, the residual bromoV filtered out, SA re-precip'd in cold water (purity 99,0-99,4%, yield 95-97%)

The article has no mention of copper 2+ and doesn't have anything else on prep'n of TMBAfrown  Quite possible, it was a misprint... What about that ref,  Rao D., Stuber S.A. A convenient synthesis of 3,4,5-trimethoxybenzaldehyde from vanillin // Synthesis (BDR). 1983.4. S. 308. ? I bet they took it from there as there's no other ref related to the subj in the article.

Hope the improved bromination proc. will be useful to Some People I Never Met :)


P.S. Karel, do i know you? winkwinkwink If not, take a look here if you care: http://www.voy.com/12987/
07-22-01 22:01
No 198111
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Karel: This user is no longer in our database. That's fast. Overly cautious?
Do you speak and write Russian, besides Dutch? Do I know you also, and do you have now a russian (girl)friend to translate? If yes, that's funny and handy. cool LT/
PS: I miss Assholium also, that russian?(many former EastGermans, Polish and other eastblock nationals speak russian) guy KNEW his chemistry, and also how to stay free, hope he still is.

(Stranger / Eraser)
07-23-01 20:37
No 198382
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Nice to meet you, Antoncho. Really interesting forum.smile
Best regards, LaBTop. Although I'm not Russian, I can speak
and write this language. I am prepared to help with

07-26-01 17:46
No 199075
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Rationale to add Cu2+  is that copper ion chelatizes with free phenolic OH group and aids to hydrolyse the neighboring halogen (this trick is working with iodovaniline too, maybe even a bit easier)

But now another question - do one really need to hack off that halogen, or in other words - how useful are 3-bromo-4,5-dimetoxy-A or PEA (or iodo instead of bromo, or ethoxy in 4 place - all made very easy)?  I quickly scanned over PIHKAL, seems that these compounds are not described there. Are they complete crap, or have just somewhat fallen through cracks?

(Hive Bee)
07-26-01 18:46
No 199090
      Re: High-yield 3,4,5-TMB synth from vanillin (Russ  Bookmark   

Probably also active. But if you do reductions with LAH, use one equivalent of LAH or LAH will chew off the halogen.
07-30-01 03:33
No 199892
      Re: High-yield 3,4,5-TMB synth from vanillin (Russ  Bookmark   

I doubt that under mild conditions (like ether as solvent) LiAlH4 will debrominate the ring. If you want to play safe use AlH3 as the reducing agent, prepared from LiAlH4 and AlCl3 in situ.
08-18-01 02:37
No 205524
      Re: High-yield 3,4,5-TMB synth from vanillin (Russian)  Bookmark   

Can you post the method you cited, please?

I dunno, but I been told ... You never slow down, you never grow old!