Keras
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p-Toluenesulphonic acid → 4-anisaldehyde
Folks,
now that I've successfully made phenethyl alcool using hydroboration, I’m turning to 4-anisaldehyde.
The path I thought of is this:
1. p-Toluenesulphonic acid + NaOH (fused) → p-Cresol
2. p-Cresol + Na (or NaOH?) → sodium p-Cresolate
3. Sodium p-Cresolate + Methyl iodide → 4-methylanisole
4. 4-methylanisole + (some oxidant) → 4-anisaldehyde
While 1. 2. and 3. are relatively straightforward, I wonder about 4. I've read various threads here about oxidation of toluene to benzaldehyde, the
most obvious way being Cr (VI), but I would like to avoid the use of chromium VI salts. Would Oxone (potassium peroxymonosulphate) work? Or ammonium
persulfate? I have potassium permanganate, but that would over-oxidise the aldehyde.
Any idea, anyone?
TIA!
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Bedlasky
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DMP oxidize alcohols to aldehydes without overoxidation.
https://en.m.wikipedia.org/wiki/Dess%E2%80%93Martin_periodin...
TEMPO and DMSO oxidations are another option.
https://en.m.wikipedia.org/wiki/Swern_oxidation
https://en.m.wikipedia.org/wiki/TEMPO
But that's just my teoretical knowledge, I don't have any practical experience with it.
[Edited on 29-9-2022 by Bedlasky]
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Keras
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DMSO is out of stock anywhere, due to COVID, I heard (well actually I have 1L of it, so I don’t care). TEMPO might be hard to get, and so is
probably the periodate compound.
But anyways, that’s not what I’m looking for. I’m looking for a way to oxidise the -CH₃ group into -COH, either directly or in two steps, but
preferably avoiding reducing from the carboxylic stage which permanganate would led me to (because I want to spare the use of my sodium borohydride
stock, although sodium sulphite might work?)
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clearly_not_atara
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Would suggest switching the order and use the CoCl2-catalyzed aerobic oxidation to convert p-cresol to p-hydroxybenzaldehyde from here:
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
and using Na2CO3 and dimethyl oxalate in methanol to methylate in the last step.
[Edited on 04-20-1969 by clearly_not_atara]
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Bedlasky
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Oh, sorry, I automatically think about aldehyde from alcohol  .
If you don't want work with chromyl chloride due to its volatility, maybe pyridinium chlorochromate will work. I am not telling that it will work, its
just guess based on similar composition.
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Keras
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Do you think Na₂CO₃ is basic enough to convert 4-hydroxybenzaldehyde to the 4-oxybenzaldehyde anion?
[Edited on 30-9-2022 by Keras]
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Keras
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Quote: Originally posted by Bedlasky  | Oh, sorry, I automatically think about aldehyde from alcohol .
If you don't want work with chromyl chloride due to its volatility, maybe pyridinium chlorochromate will work. I am not telling that it will work,
it's just guess based on similar composition. |
That’s still chromium something, and I’m not sure pyridinium chlorochromate would oxidise the methyl group into an aldehyde. Might happen, but I'd
check for it in the literature before attempting it.
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clearly_not_atara
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CoCl2 is catalytic, so there's gotta be a way to order a smaller amount. You shouldn't need 250 g!
[Edited on 04-20-1969 by clearly_not_atara]
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Keras
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Yes, you’re right. Other sources sell it in smaller, cheaper quantities, like 25 g.
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Lionel Spanner
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For what it's worth, the industrial process for producing 4-anisaldehyde from 4-methylanisole uses manganese dioxide as the oxidant.
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Keras
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| Quote: Originally posted by Lionel Spanner | | For what it's worth, the industrial process for producing 4-anisaldehyde from 4-methylanisole uses manganese dioxide as the oxidant.
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That’s right, but I’m a bit weary of industrial processes, because they often require high temperatures and impossibly high pressures. I’m not
sure manganese dioxide would work under mild conditions, and if it does, then what is the result of the oxidation?
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tyro
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How about the manganese ammonium alum or other elecrolytic methods mentioned in the toluene->benzaldehyde thread stickied in the organic section
and in a separate thread?
https://www.sciencemadness.org/whisper/viewthread.php?tid=22...
http://www.sciencemadness.org/talk/viewthread.php?tid=6882
Seems one a patent referenced in the second link mentions methoxytoluene, though I didn't notice any test or confirmations of that particular method
being done here.
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