Dope Amine
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Benzyllic Ketone Catalytic Transfer Deoxygenation (paper request)
Hi all! I am searching for a way to completely remove a benzyllic ketone (deoxygenation) which will not also affect ethers (like
methylendioxyphenyl). I'm not sure how relevant this also might be but there is also a non-aromatic secondary amine group alpha to the ketone. I
should also mention that high pressure reactions such as hydrogenations are not an option for me.
Raney Nickel and Raney Cobalt would be options but my fear is that they would also reduce the ethers.
I know that thionyl chloride would convert the ketone to O-Cl but I'm not sure how much easier that would be to reduce to an alkane. Might it also
react with the secondary amine?
A longer way about it would be to reduce the ketone to an alcohol, swap it out with a chlorine, and then remove the chlorine.
Here is the one promising lead I have for a direct route: catalytic transfer reduction using Pd/C, a Lewis acid such as FeCl3, and lemonene
or cyclohexene.
Could someone please help me with acquiring this article:
Catalytic transfer reduction of carbonyl compounds
Gottfried Brieger and Tzuu-Heng Fu
J. Chem. Soc., Chem. Commun., 1976, 757a-757a
DOI: 10.1039/C3976000757A
If this is the best viable route then my one question would be if potassium formate and water (1:3 ratio is supposedly optimal) would be an acceptable
substitution or even an improvement over lemonene or cyclohexene. I believe formates are most commonly used in CTH reactions with Pd/C.
Help with the article is greatly appreciated! Thank you in advance!
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tetrahedron
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here's some sample replies you'll get: https://www.sciencemadness.org/whisper/viewthread.php?tid=76...
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jon
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that's on rhodium's page, boy you sure like CTH.
it is done in acetic acid at higher temps
i don't feel like running through it all to find it atm but i've seen examples and those are the conditions: ammonium formate acetic acid, Pd/C 10%
and 110C for 3 hours i think if memory serves.
i never was to motivated to do that i was just examining the conditions that reduction of benzylic alcohols/ketones take place, and they always
involve high temps and acetic acid.
under catalytic transfer methodology you know as a warm up to the last bit of fun we had because our substrate had a tertiary alcohol i did'nt want to
see get snipped off.
here is what you want
http://www.erowid.org/archive/rhodium/chemistry/cth.carbonyl...
and see table 1
http://www.erowid.org/archive/rhodium/chemistry/pictures/cth...
[Edited on 10-11-2012 by jon]
[Edited on 11-11-2012 by jon]
[Edited on 11-11-2012 by jon]
Give me librium or give me meth!
Patrick Henry....
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Nicodem
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Thread Moved
11-11-2012 at 00:53 |
Dope Amine
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I absolutely DO love CTH's because I don't have the $5,000+ to pay for a safe hydrogenation setup. Oxygenations and reductions tend to be very useful
for the organic chemist.
Now that you mentioned that you mentioned it, Jon, I hadn't considered removal of the hydroxy group at the same time as the aryl dehalogenation. Not
only was that a tertiary alcohol, it was a benzylic tertiary alcohol! Aye-aye-aye!!! Who knows whether that propionyl chloride got wasted cuz the
hydroxyl had already left the building.
From what been able to find. It appears that benzylic ketones/alcohols are easier to reduce than normal ketones. I know that potassium formate
should deoxygenate that benzylic ketone. Not sure whether a Lewis acid is needed or if it would help spell doom for the ether linkages. FYI I always
had to reduce a certain imine in an ice bath. Otherwise, I would get a darkening of the reaction solution from unwanted byproducts. So I would be
trying the reduction cold, hoping that potassium formate dooes the trick. Potassium formate with a little AlCl3, appropriate water to
formate ratio and a looooong cold reaction time would be my bet.
Here's another promising paper that reports to be highly selective (gentle). It would be exceedingly helpful if only someone would be so kind as to
share it:
Reductive deoxygenation of aryl aldehydes and ketones and benzylic, allylic, and tertiary alcohols by zinc iodide-sodium cyanoborohydride
J. Org. Chem., 1986, 51 (15), pp 3038–3043
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