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Author: Subject: Catechol preparation
Chemi Pharma
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[*] posted on 12-3-2018 at 09:17


Reading this topic I remembered a study I've saw, telling about formylation of phenols with 80% yields.

They used anhydrous MgCl2, EtN3 and Paraformaldehyde in THF at reflux and this is described at orgsyn.

From the salicylaldehyde formed is easy to get cathecol by using H2O2 in basic media. This is also described at orgsyn.

The both synthesis is attached below:

Attachment: formylation of phenols - MgCl2 + Et3N + paraformaldehyde in THF.pdf (535kB)
This file has been downloaded 43 times

Attachment: CATECHOL from Salicylaldehyde or guayacol.pdf (168kB)
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[Edited on 13-3-2018 by Chemi Pharma]
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Magpie
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[*] posted on 1-4-2018 at 13:27


Does anyone know the reaction mechanism for this overall reaction?


Catechol chemsketch equation gif.gif - 3kB

Attachment: catechol chemsketch equation.sk2 (2kB)
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[Edited on 1-4-2018 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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Sigmatropic
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[*] posted on 1-4-2018 at 15:07


Protonation of the phenol methyl ether and substitution with bromide giving methyl bromide which off gasses, and cathechol. Pretty similar to phenol demethylation by boron tribromide just under much harsher conditions.
http://commonorganicchemistry.com/Rxn_Pages/O_Demethylation/...
Edit: on clicking some more here is the actual mechanism :
http://commonorganicchemistry.com/Rxn_Pages/O_Demethylation/...

[Edited on 1-4-2018 by Sigmatropic]

O-Demethylation_BBr3_Mech.png - 20kB
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Magpie
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[*] posted on 1-4-2018 at 17:47


Thanks very much!



The single most important condition for a successful synthesis is good mixing - Nicodem
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JJay
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[*] posted on 1-4-2018 at 21:56


I was actually just reading about this reaction in Preparative Organic Chemistry (in the SM library) yesterday. Apparently, a very wide range of acids can be used, but boron tribromide will dealkylate phenyl alkyl ethers if added at dry ice temperatures and allowed to warm to room temperature.



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