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Topic: Carboxylic acid - CH3 substitution  (Read 11876 times)

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Offline doof

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Carboxylic acid - CH3 substitution
« on: December 20, 2009, 11:39:56 PM »
What is the easiest way to substitute a carboxylic acid for a CH3 group? And preferably the safest way too

Offline Dan

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Re: Carboxylic acid - CH3 substitution
« Reply #1 on: December 21, 2009, 07:41:02 AM »
For R-COOH --> R-CH3 there are a number of approaches, here are some suggestions.

Aldehydes can be reduced to alkanes (RCHO --> R-CH3) by:

1. Wolff-Kishner - Basic
2. Clemmensen - Acidic
3. Mozingo (Raney Ni reduction of a corresponding thioacetal) - neutral

The aldehyde can be obtained from the acid by partial reduction via the ester or amide with DIBAL, or catalytic hydrogenation via the acid chloride, for example.

Alternatively, you could reduce the acid all the way down to the primary alcohol with LAH and substitute with, for example, a halide - which can then be removed by catalytic hydrogenolysis, or radically with Bu3SnH.
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Offline Schrödinger

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Re: Carboxylic acid - CH3 substitution
« Reply #2 on: December 21, 2009, 07:49:08 AM »
How about HI/P(red)  reduction?

It is one of those reductions of a carboxylic acid directly to CH3 group without destroying the Carbon of the COOH group like is done during decarboxylation.
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Offline doof

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Re: Carboxylic acid - CH3 substitution
« Reply #3 on: December 23, 2009, 08:43:22 PM »
thanks :)

Offline doof

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Re: Carboxylic acid - CH3 substitution
« Reply #4 on: January 20, 2010, 05:19:48 AM »
How about HI/P(red)  reduction?

It is one of those reductions of a carboxylic acid directly to CH3 group without destroying the Carbon of the COOH group like is done during decarboxylation.



Is HI/P(red) reactive enough to reduce a carboxylic acid?

Offline Schrödinger

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Re: Carboxylic acid - CH3 substitution
« Reply #5 on: January 20, 2010, 05:47:02 AM »
As far as I know, yes
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Offline orgopete

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Re: Carboxylic acid - CH3 substitution
« Reply #6 on: January 20, 2010, 10:06:43 AM »
I might be interested in that reaction also. Do you have a reference for HI/P to convert a carboxylic acid to a methyl group?
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Offline doof

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Re: Carboxylic acid - CH3 substitution
« Reply #7 on: January 27, 2010, 04:43:34 AM »
As far as I know, yes

and how far do you know exactly? have you read a journal article showing that is works? have you done the experiment yourself? read it on the net somewhere? or just having a guess? can you please elaborate on what convinces you that it will work?

Offline Schrödinger

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Offline doof

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Re: Carboxylic acid - CH3 substitution
« Reply #9 on: January 28, 2010, 03:51:16 PM »
cheers man :)

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