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Topic: Selectively reducing polyfunctional compounds  (Read 1458 times)

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Offline Altered State

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Selectively reducing polyfunctional compounds
« on: September 18, 2013, 02:19:45 PM »
I'm interest in knowing what is the best way to reduce selectively some insaturated functional groups in a molecule.
The example that I have in mind is one compound with one alkene group and an aldehyde carbonyl.
What's the best way of just hydrogenating the alkene? Do I need to protect carbonyl with, for example, ethylenglycol + TsOH, then reduce double bond (with H2/Pd), and then recover aldehyde in acid media?
Or is there any reagent that allow to do this reduction selectively in one step?

I know that LiAlH4 wont hydrogenate alkene, just will reduce aldehyde, but H2/Pd will reduce both. Is there any easy way to do exactly the opposite?

Offline discodermolide

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Re: Selectively reducing polyfunctional compounds
« Reply #1 on: September 18, 2013, 02:24:30 PM »
I think that mild hydrogenation should be ok for reduction of the C=C.
If the catalyst is a bit too active you can always change to one of the poisoned catalysts which are less active.
Or do the reaction in the presence of traces of pyridine, or other tertiary amines.
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Offline Altered State

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Re: Selectively reducing polyfunctional compounds
« Reply #2 on: September 18, 2013, 02:42:34 PM »
Ok, so there is no point in protecting, just H2 and poisoned catalyst (0ÂșC?, don't know what exactly you mean by "mild") will hydrogenate the olefin and leave carbonyl.
Thank you very much.

Offline discodermolide

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Re: Selectively reducing polyfunctional compounds
« Reply #3 on: September 18, 2013, 02:47:20 PM »
Mild means normal pressure and temperature.
If the carbonyl partially reduces, use the less active catalyst.
Houben-Wehyl had a volume(s) on hydrogenation, if you have access have a look.

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