goldberg
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Syringol from pyrogallol
Has anybody tried to synthetise syringol from pyrogallol?
In theory this is typical synthesis of phenyl ehters but how to selectivly methylate only two OH groups?
How about slow addition of MeI + NaOH to solution of pyrogallol?
OH groups at positions 1 and 3 should be more vulnerable to methylation due to steric effect if my reasoning is correct.
I'm also thinking how to separate syringol from trimethoxypyrogallol.
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karlos³
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Syringol is a phenol so it should be easy to separate it from the fully trimethoxylated compound by forming a phenolate salt.
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goldberg
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Right, thanks for reminding me that. In theory there is also possibility to get 2,3dimethoxy phenol and it will also form salt with NaOH.
Any tips about exact conditions to maximise yield?
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TheMasterOfTheInternet
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Quote: Originally posted by karlos³  | | Syringol is a phenol so it should be easy to separate it from the fully trimethoxylated compound by forming a phenolate salt. |
When you methylate pyrogallol will end up with a mix several products
1) 1,2,3-trimethoxybenzene
2) 1,2-dimethoxy-3-hydroxybenzene
3) and Syringol
and some crap
1) can be seperated by adding a strong base
2 and 3) and crap can be seperated fractionated vacuum-destillation.
Though I guess the yield you be low as you're producing three components in the same reaction.
I would look for a more selevtive route unless you find literature about this particular synthesis.
Is syringol your final target or will be something attatchted at the para-position?? What about staring from 5-bromovanillin (very easy to make in
high yield from vanillin with basic chemicals, a very satisfying synthesis)
Check this using google translate http://www.lambdasyn.org/synfiles/bromovanillin.htm
Or Guajacol+Oxidant+KBr+EtOH?
[Edited on 18-7-2020 by TheMasterOfTheInternet]
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goldberg
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@TheMasterOfTheInternet: Finally i would like attach something to para position. Pyrogallol is cheap as photographic developer and that's why i'm
thinking about it.
I did not found any literature about synthesis of syringol.
Vanilin is much more expensive and less avaiable at least in places where i have looked for it.
How about steric effect in this methylation? Would they be important here?
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TheMasterOfTheInternet
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| Quote: Originally posted by goldberg | @TheMasterOfTheInternet: Finally i would like attach something to para position. Pyrogallol is cheap as photographic developer and that's why i'm
thinking about it.
I did not found any literature about synthesis of syringol.
Vanilin is much more expensive and less avaiable at least in places where i have looked for it.
How about steric effect in this methylation? Would they be important here? |
Maybe you have too look a little further 
I can find several synthesis routes for syringol
I think it's usually made from lignin
http://www.molbase.com/moldata/4396.html
Vanilin is a very common food additive, sold in drums and 20kg bags.
Where do you live? I almost can't believe that it's hard to find for you. Last time I bought 500g for less than 25€ incl. shipment from an
online-pharmacy.
I can even find it on Amazon and Ebay for less than 40€/kg
Food grade is usually 98%+ so very suitable for synthesis.
Vanillin+KBr+H2O2 or other Oxidant in acetic acid as solvent=5-Bromovanillin
5-Bromovanillin can be methoxylated by alkali-methanolate using Cu-salts (CuCl2 or Cu(I)Br)
Sodium methanolate can be made in situ by alkali + methanol OR alkali hydroxide + methanol + mol sieves in situ
Ethanol+CuBr+Base gives 3-Methoxy-4-Hydroxy-5-Ethoxybenzaldehyde
Syringaldehyde+ EtBr + K2CO3 in DMF gives 3,4-Dimethoxy-4-Ethoxy-benzlydehyde
5-Bromovanillin can be also be used quite easily to make 3,4-Dihydroxy-5-Methoxy-benzalhyde and from that 3,4-Methylendioxy-5-Methoxy-benzaldehyde and
maaaany other interesting aromas
A great basic material for hobby chemistry 
[Edited on 18-7-2020 by TheMasterOfTheInternet]
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goldberg
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@TheMasterOfTheInternet: thanks. i have looked again and have found better sources for vanilin.
I have no sodium nor alkoxides, could You please post here reference (even just DOI for paper will be very helpful) for using alkali hydroxide,
methanol and molecular sieves instead of sodium methanolate?
How about solubility of NaOH in MeOH? I have tried to prepare solution of NaOH in EtOH and iPOH as cleaning mixture and it never dissolved without
addition of water.
Idea with ligning sounds interesting, unfortunately on site You have posted link to i have to register to see details but i'll look for more
information on my own.
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monolithic
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What about USA? I'm not seeing anything less than $30 for ~500 g.
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deep_dreamer
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| Quote: Originally posted by goldberg | @TheMasterOfTheInternet: thanks. i have looked again and have found better sources for vanilin.
I have no sodium nor alkoxides, could You please post here reference (even just DOI for paper will be very helpful) for using alkali hydroxide,
methanol and molecular sieves instead of sodium methanolate?
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https://www.sciencemadness.org/whisper/viewthread.php?tid=70...
I think this is the thread where that idea originated from. It seems like this Ullmann variation is quite tricky, but if it works, yield seems to be
good (in the literature). You'll have to know how to work (almost) completely anhydrous.
User "Ullmann"'s preparation of OTC sodium methoxide 3N:
https://www.sciencemadness.org/whisper/viewthread.php?tid=99...
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