beeology
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Piperonal from Ethylvanillin
The aim of this work was to develop a simple yet reproducible method for the synthesis of piperonal using readily available, only slightly toxic or
untoxic chemicals. The synthesis takes place in two steps, each carried out in a home-built autoclave at comparatively low temperatures
(70–85 °C) in a water bath. The setup is simple: just add the reagents to the reactor, seal it, and leave it in the water bath for a calculated
amount of time - minimal workup required.
1. Ethyl vanillin (32.2 g, 200 mmol) was added with stirring to concentrated sulfuric acid (196.6 g, 106 mL, 2000 mmol) in a PVDF-lined
stainless steel autoclave. The autoclave was purged with argon, sealed, and placed in a water bath at 70 °C for 4 hours under continuous stirring.
After completion of the reaction, the mixture was cooled to room temperature and poured onto 420 g of crushed ice in a 1000 mL Erlenmeyer flask.
Stirring was continued until a solid precipitate formed. The supernatant was decanted, and the solids were collected by filtration. The crude product
was obtained as a light gray crystalline mass. It was recrystallized twice from hot water (approximately 80 mL at 60 °C). During the second
recrystallization, the still-hot saturated aqueous solution was subsequently washed with 30 mL of xylene. After separation and cooling, pure
protocatechualdehyde crystallized from the aqueous phase. Yield after drying: 17.4 g, 65%; melting point: 152 °C. This product was used in the
subsequent step without further purification.
2. Protocatechualdehyde (11.7 g, 85 mmol) and tetrabutylammonium bromide (2.7 g) were added to a cooled solution of sodium hydroxide (10.2 g,
225 mmol) in water (85 mL) in the autoclave. After complete dissolution, dichloromethane (85 mL) was added. The autoclave was filled with argon,
sealed, and kept in a water bath at 85 °C for 6 hours with continuous stirring. After this period, the reaction mixture was cooled to room
temperature, and the excess dichloromethane was recovered by simple distillation.
The product was isolated by steam distillation; a total of 500 mL was collected. The distillate was saturated with NaCl and extracted with a total
of 40 mL of dichloromethane. 3.8 g of crude piperonal was obtained after evaporation (30% yield).
Production of protocatechualdehyde, Patent JPH10265428A
High Selectivity in the Oxidation of Mandelic Acid Derivatives and in O-Methylation of Protocatechualdehyde
 
the autoclave and crude protocatechualdehyde settled down in the ice water
 
crude and twice recrystallized protocatechualdehyde
 
steam distillate and crude piperonal after dichloromethane evaporation
[Edited on 30-9-2025 by beeology]
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Niklas
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Great to actually see this methenylation method being attempted here, unfortunately not the 70% yield stated in the patent (unsurprisingly honestly),
but still a good comparison to have as without a pressure vessel using DMF / potassium carbonate / TBAB I also only managed to achieve 40% at most so
far, although I should soon be doing some more work in that regard in hopes of improving this value (though at this point I really do start
to believe it’s much easier and cheaper to just buy some piperonal acetals as perfume substances and then hydrolize them).
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DraconicAcid
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I've been wanting to try this, but don't have TBAB or a pressure vessel.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Mateo_swe
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Very nice.
Have you tried with plain vanillin as starting material and if so what was the yield of the first stage?
If one reads the papers related to this they state that the pressure developed is quite low.
So one can use a glass pressure bottle or a DIY solution if you dont own a hydrothermal reactor vessel.
If i remember correctly the pressure rised to 2.4 atmospheres.
I hope the last stage can be improved so that more than 30-40% yield can be had.
There are many variations of this procedure that one can try.
Substituting the dichloromethane for the dibromo variant is said to improve yields but unfortunatley its not so easily found as DCM.
Very intresting, plz continue the experimentation.
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beeology
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Thank you for your feedback.
So far, I have only worked with ethylvanillin, as it is relatively straightforward and requires only sulfuric acid for the conversion. Working with
protocatechualdehyde is a bit delicate and consistently yields variable results, even under seemingly identical reaction conditions. Unfortunately,
commercially available protocatechualdehyde is quite expensive.
According to the paper cited above, an effective yield of 37.5% was achieved in the methylenation step, which is likely the upper limit using this
method. My current approach is to add the reagents in stages to the autoclave, as described in the patent. A pressure gauge would be a useful
addition.
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Niklas
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Demethylating vanillin is significantly more difficult and expensive unfortunately, either methods just genuinely suck like using pyridine
hydrochloride, don’t seem to work at all, or are just pretty expensive if you need a decent amount (I found Pyridine and aluminum chloride to work
pretty well (I got up to about an 80% yield in one run iirc) but at that point at least for me it’s cheaper to just buy protocatechulic aldehyde).
Deethylation on the other hand just needs sulfuric acid, you don’t even need an autoclave as has been reported here before (https://www.sciencemadness.org/whisper/viewthread.php?tid=15... , yields stated there are a bit lower, but I personally found the amount of water
Diachrynic is stating for the recryst to just be somewhat excessive). Also bourbonal isn’t that much more expensive than vanillin as it’s also
widely used as a perfume and flavoring substance.
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