Author Topic: Benzaldehyde + MEK acid catalyzed aldol  (Read 11816 times)

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bio

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B/V recycling
« Reply #40 on: October 14, 2004, 06:05:00 AM »
Another good batch of reading material you found, psychokitty.

I have been intending to try the "distill direct" method for the MePhBuO, after mechanical HCl removal, from the article you posted.  Also extracting with PhMe or Hexane from the start helps minimize emulsions and the washings go fast. But why even wash if it's not needed.

I've gone straight to the oxidation w/o crystallizing (fractionate only) but yields suffered somewhat. You can crystallize w/o distilling with good results but it is much easier and faster to just distill it.  Also it does help to keep the condensation mixture cold to avoid tar formation and process it right away if it sets solid faster than usual. Had one batch setup in 6 hours (11 hours from gassing).

Regarding your statement...............

All the authors are trying to say is that because the use of sodium perborate is so exceptionally selective, there won't be any byproducts to the reaction, and whatever starting materials are left over--in this case, the intermediate aldol condensation product of benzaldhyde and MEK--can be reused in another sodium perborate Baeyer-Villiger reaction................

Yes, this is also my understanding. My request for suggestions was >>>>>WHERE>>>>>> do you think would be the best place in the procedure? The unreacted unsaturated ketone could be isolated before the hydrolysis step in pure form by fractionating, but perhaps this would not be necessary. The ester made it through once (the oxidation) why not just run it again. Water removal might be the sticking point here though.

Ever wonder why they call them LABORatories? I think you know what I mean. Not enough hours in the day,  without the technicians and assistants, to do it all.

indole_amine

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?
« Reply #41 on: November 07, 2004, 04:14:00 PM »
What was the final yield of purified propanone with the described procedure?


indole_amine

bio

  • Guest
Results
« Reply #42 on: November 07, 2004, 09:22:00 PM »
Glad to hear it's working, abacus. I had just about given up hope that anyone was going to try the method.

You must be in favor with the  Aromatic Butenone Gods, not experiencing the "tar from hell" yet. Any theories why? Using RA ingredients I always had varying amounts especially after it sat more than 24 hours at ambient before workup.

Your DCM extraction right up front is good. I have been using Hexane and also washing with base before water to minimize emulsions but the brine wash is at the end to remove water. Hexane or Petroleum Ether seem to be the best for crystallization.

However, this is history now per my previous post. Surprisingly when fractionated after using the  JACS 54, 336 condensation method the MePhBuO came over a tighter range than ever before (about 8 degrees) and crystallized very nicely. Keeping at ice temp for the 16 hours was an idea from a previous run with better yield when the condensation mix was kept in the gassing ice bath (no stirring) for about 8 hours.

Am convinced there is a non-exotic catalyst to get the yield way up. Sulfuric Acid in varying concentrations is used in many similar Peracid oxidations but my sense is that it would tend to form the epoxide or hydroxy epoxide. The recycle method may well do that although requiring a lot of work. Am still researching Mn catalysts and the sulfates come out on top.

Please do post your continued findings or PM as I pretty much stopped posting as no one really seemed interested. Maybee there are other "closet" cases like you, LOL.

n00dle

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Of any use? Oxone/dioxirane is easy to come by.
« Reply #43 on: November 08, 2004, 06:25:00 AM »
On the Mechanism of the Bayer-Villiger Oxidation of Ketones by Bis(trimethylsilyl) Peroxomonosulfate. Intermediacy of Dioxiranes
Camporeale, M.; Fiorani, T.; Troisi, L.; Adam, W.; Curci, R.; Edwards, J.O., J. Org. Chem., 55, 93-98 (1990)

Dimethyldioxirane Epoxidation of ?,?-Unsaturated Ketones, Acids and Esters
Adam, W.; Hadjiarapoglou, L.; Nestler, B., Tetrahedron Lett., 31, 331-334 (1990)

Epoxidation of Silyl Enol Ethers, Phthalides, and Enol Esters by Dimethyldioxirane
Adam, W.; Hadjiarapoglou, L.; Wang, X., Tetrahedron Lett., 30, 6479-6500 (1989)

abacus

  • Guest
Bio I agree, washes were much easier when the...
« Reply #44 on: November 08, 2004, 11:01:00 AM »
Bio

I agree, washes were much easier when the organics were diluted in a suitable solvent.

Toluene extractions were favoured for the Baeyer Villager.

Indole

Yield P2P from experiments on stated scale were around 138g when using vacuum distillation.

Other experiments that involved steam distillation to isolate the post reaction P2P resulted in a bit less.

Thats about it from me.
Abacus

lugh

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P2P in +90% yields
« Reply #45 on: November 10, 2004, 02:26:00 AM »
In this article, p2p is synthesized by oxidation of trans beta methyl styrene in yields of over 90%  :)

On the Mechanism of the Bayer-Villiger Oxidation of Ketones by Bis(trimethylsilyl) Peroxomonosulfate. Intermediacy of Dioxiranes
Camporeale, M.; Fiorani, T.; Troisi, L.; Adam, W.; Curci, R.; Edwards, J.O., J. Org. Chem., 55 93-8 (1990)



8)


bio

  • Guest
epoxide/ester hydrolysis
« Reply #46 on: November 11, 2004, 10:33:00 PM »
Thanks for finding that , lugh. Any chance of locating the 3rd one nOOdle posted?

What I'm not entirely sure about is if the epoxide was made from the MePhBuO rather than the ester would it hydrolyse to the same product (2propanone)? Would try this if there is a known procedure similar enough to be adapted to the MPB.

 Am thinking of using chromics HCl  rearrangement procedure for the hydrolysis of the ester. Is this really adaptable as is to unsaturated ketonic ester hydrolysis? Having a hard time finding one that uses acid instead of base. Vogel mentions sulfuric acid in acetic acid for ketonic ester hydrolysis but no experimental except for many base examples.

Also in the 90% article,  J. Org. Chem., 55, 93-98 (1990),  the trans beta methyl styrene is also called propenyl benzene, correct?

Rhodium

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trans-?-methylstyrene propenylbenzene
« Reply #47 on: November 11, 2004, 11:57:00 PM »
trans-?-methylstyrene is also called propenylbenzene, correct?

Correct.


psychokitty

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New info . . .
« Reply #48 on: November 12, 2004, 02:36:00 AM »
First of all, the hydrolysis occurs in most publications that I've read using KOH, NOT NaOH.  Maybe that'll make the difference.

As for recommendations as to how the syntheses protocol can be modified to advantage, it would seem that using potassium (or perhaps sodium) acetate in the peracetic acid reaction is the ticket.  Apparantly, it allows the reaction to complete in shorter time (1 HOUR!), with fewer side-reactions, and overall better yields.   Also, use of a saturated acetate salt mixture allows substituted (as in methylenedioxy-substituted) a,B-unsaturated ketones to be used as precursors to ring-substituted enol-esters, which are produced in good yield. 

As for the dilution factor, in many of the articles that I've read (already mentioned), the percentage of acetic acid doesn't seem to impact the final yield of product, so my best guess is that Chromic's method should work well if not wonderfully.  The only catch is the use of a halohydrocarbon solvent as part of the biphasic peracid reaction mixture.  While this works wonders for making epoxides and diols out of alkenes, I wonder what it's effect will be when applied to the Baeyer-Villiger reaction.  DCM/performic acid has already been published as an effective reagent for the Baeyer-Villiger reaction using ketones as precursors.  But I have yet to find even one publication describing its use as  would be applied to a,B-unsaturated ketones.

Aside from the acetate salt issue, lowering the temperature of the reaction to about 0°C seems to be the only other factor which might merit modification.

Let me know if you have any additional questions, anyone.