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Niklas
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So I just rewatched Sam‘s Lugduname video (https://youtu.be/YdGalCuJ96Q?si=G7DkvF4hivI_6Eki), where he made the ortho isomer of piperonal as an intermediate, and to make it he used the
rather interesting approach of catalyzing the methylenedioxy-synthesis with copper(II)-oxide, I presume to achieve an Ullmann-condensation kind of
mechanism.
Literature claims 90%, and while it is using dibromomethane, I now wonder how well this procedure could be applied to protocatechulic aldehyde using
DCM, as it‘s definitely a lot more accessible than any of the quaternary ammonium catalysts I‘m personally trying to employ.
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underground
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Quote: Originally posted by Niklas  | So I just rewatched Sam‘s Lugduname video (https://youtu.be/YdGalCuJ96Q?si=G7DkvF4hivI_6Eki), where he made the ortho isomer of piperonal as an intermediate, and to make it he used the
rather interesting approach of catalyzing the methylenedioxy-synthesis with copper(II)-oxide, I presume to achieve an Ullmann-condensation kind of
mechanism.
Literature claims 90%, and while it is using dibromomethane, I now wonder how well this procedure could be applied to protocatechulic aldehyde using
DCM, as it‘s definitely a lot more accessible than any of the quaternary ammonium catalysts I‘m personally trying to employ.
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What is also interesting is that he is also using Glacial AA and 48% HBr for the cleavage reaction in inert atmosphere with 48% yields. No pyridine,
no ALCL3. Just distill some HBr from a Br salt + drain cleaner and you are ready.
[Edited on 20-1-2025 by underground]
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Niklas
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| Quote: Originally posted by underground |
What is also interesting is that he is also using Glacial AA and 48% HBr for the cleavage reaction in inert atmosphere with 48% yields.
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Indeed, definitely wouldn’t have expected much more than maybe 20% with that approach.
I honestly can’t believe it would work this well for normal vanillin as well, like logically it should, but it can’t be that nobody tried that one
and we are still rather using stuff like the AlCl3 / Py demethylation..
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underground
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| Quote: Originally posted by Niklas | | Quote: Originally posted by underground |
What is also interesting is that he is also using Glacial AA and 48% HBr for the cleavage reaction in inert atmosphere with 48% yields.
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Indeed, definitely wouldn’t have expected much more than maybe 20% with that approach.
I honestly can’t believe it would work this well for normal vanillin as well, like logically it should, but it can’t be that nobody tried that one
and we are still rather using stuff like the AlCl3 / Py demethylation.. |
LoL i was editing but you was faster 
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Niklas
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Haven‘t yet had the time to continue with figuring out this synthesis, but while browsing Lamdasyn I came across a mention of a procedure making
myristic aldehyde from 5-hydroxyvanillin by the reaction with DCM in DMF with simple KF catalysis in a reasonably impressive 63,4% considering it used
neither nucleophilic nor phase-transfer catalysis.
So I guess KF may be a lot more suitable than K2CO3 for the Williamson ether synthesis using bad electrophiles like DCM.
Attachment: Structure and Synthesis of (+-)-Wuweizisu C - J. Org. Chem.; 1981; 46(14); 2969-2971.pdf (135kB)
This file has been downloaded 11 times
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clearly_not_atara
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| Quote: Originally posted by Niklas | | Quote: Originally posted by underground |
What is also interesting is that he is also using Glacial AA and 48% HBr for the cleavage reaction in inert atmosphere with 48% yields.
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Indeed, definitely wouldn’t have expected much more than maybe 20% with that approach.
I honestly can’t believe it would work this well for normal vanillin as well, like logically it should, but it can’t be that nobody tried that one
and we are still rather using stuff like the AlCl3 / Py demethylation.. |
Everybody thinks you can skip the inert atmosphere and then they get bad yields and blame the method
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Niklas
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Yeah that seems like a fair assumption, protocatechulic aldehyde is reasonably oxygen sensitive, and especially in such harsh conditions with such
lengthy reaction times it will most definitely cause some problems.
But yeah I guess that’s good to keep in mind, if anyone decides to give things a shot make sure to report on it.
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