underground
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Double bond ox. cleavage to aldehyde with CuO
From the patent US2516412A
https://patentimages.storage.googleapis.com/23/db/8f/1e3b03d...
Quote: | EXAMPLE VII: Syringaldehyde from the isolated intermediate
Syringaldehyde may also be prepared by oxidizing the isolated 3,5-dimethoxy-4-hydroxypropenylbenzene of Example V with nitrobenzene in alkali or other
low potential oxidizing agents.
Thus 195 parts 3,5-dimethoxy-4-hydroxypropenylbenzene are added to a cupric oxide mixture freshly prepared from 1000 parts hydrated copper
sulfate, 660 parts sodium hydroxide, and 8000 parts of water and the resulting mixture is heated to boiling under reflux for eight hours. The
separated red cuprous oxide is filtered and washed with water. The alkaline filtrate and washings are acidified and extracted with ether. Bisulfite
purification of the ether extract should yield approximately 155 parts or 90% syringaldehyde.
Other alkaline copper oxidizing agents such as Fehling's Solution, Benedict’s Solution, may be used with the same results.
An alkaline copper oxidizing agent is particularly advantageous for replacing the propenyl group with the aldehyde group because the strength
of its action in changing from a cupric to a cuprous compound is definitely adequate to oxidize to the aldehyde, and at the same time insufficient to
continue the oxidation to the acid further or to destruction.
However, in large scale operation, it will be obvious that oxidizing agents having no such automatic action may be employed for reasons of economy,
and the extent of the reaction controlled by controlling the amount of the reagent. |
So if Cuo is able to ox. cleavage 3,5-dimethoxy-4-hydroxypropenylbenzene to syringaldehyde, i do not see the reason why it wont work with other
propenyl group. For example:
styrene-->benzaldehyde
cinnamic acid-->benzaldehyde
piperic acid-->piperonal
3bromocinnamic acid-->3bromobenzaldehyde
2hydroxy cinnamic acid-->salicylaldehyde
and so on
The procedure looks super simple and high yielding
[Edited on 17-1-2025 by underground]
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Texium
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Sounds nice, but patents can sometimes be complete bunk, so you’ll have to try it out to see if it actually works. I’d suspect that freshly
prepared CuO is essential, so if you try it, prepare it the way they described, don’t just use CuO off the shelf, as it probably won’t have the
same activity, just as freshly prepared MnO2 can do a lot more than junk from a pottery store.
There’s a couple other reasons the reaction may not be so general, though. The electron donating groups on the syringaldehyde precursor might also
help to activate the alkene for oxidation, so it may be that it will work on electron rich aromatics only. The propenyl double bond is also going to
be easier to oxidize than the one in a cinnamic acid. So while the molecules you list are superficially similar in structure, there’s a decent
chance they won’t react the same way. Still, it wouldn’t hurt to try.
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6dthjd1
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Quote: Originally posted by Texium ![](images/xpblue/lastpost.gif) | Sounds nice, but patents can sometimes be complete bunk, so you’ll have to try it out to see if it actually works. I’d suspect that freshly
prepared CuO is essential, so if you try it, prepare it the way they described, don’t just use CuO off the shelf, as it probably won’t have the
same activity, just as freshly prepared MnO2 can do a lot more than junk from a pottery store.
There’s a couple other reasons the reaction may not be so general, though. The electron donating groups on the syringaldehyde precursor might also
help to activate the alkene for oxidation, so it may be that it will work on electron rich aromatics only. The propenyl double bond is also going to
be easier to oxidize than the one in a cinnamic acid. So while the molecules you list are superficially similar in structure, there’s a decent
chance they won’t react the same way. Still, it wouldn’t hurt to try. |
What could underlie the activity present in freshly prepared CuO?
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