April 26, 2024, 04:10:06 PM
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Topic: Organic synthesis  (Read 4786 times)

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Offline portugal

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Organic synthesis
« on: April 26, 2008, 05:03:51 AM »
To synthesise 1-phenyl-1,4-butanediol from the lactone of 4-hydroxybutanoic acid i would use these reagants in this order = (i) K2CO3 in dimethylformamide followed by (ii) PhMgBr with an aqueous acid workup


Offline portugal

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Re: Organic synthesis
« Reply #1 on: April 26, 2008, 09:29:45 AM »
I am not really sure about this could anyone tell me if this is a good way to synthesise it

Offline macman104

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Re: Organic synthesis
« Reply #2 on: April 26, 2008, 05:09:00 PM »
To synthesise 1-phenyl-1,4-butanediol from the lactone of 4-hydroxybutanoic acid i would use these reagants in this order = (i) K2CO3 in dimethylformamide followed by (ii) PhMgBr with an aqueous acid workup
Why are you doing K2CO3 in DMF?

Offline miraculix

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Re: Organic synthesis
« Reply #3 on: April 27, 2008, 06:07:33 AM »
I'd say it's not a good way to synthezise 1-phenyl-1,4-butanediol, because with the sequence you've mentioned, you will not end up with the desired product.


best regards

miraculix

Offline Dan

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Re: Organic synthesis
« Reply #4 on: April 27, 2008, 07:39:48 AM »
To synthesise 1-phenyl-1,4-butanediol from the lactone of 4-hydroxybutanoic acid i would use these reagants in this order = (i) K2CO3 in dimethylformamide followed by (ii) PhMgBr with an aqueous acid workup



Is the purpose of K2CO3 to open the lactone to the carboxylate? Grignards don't react (in textbooks) with carboxylates, and there will be issues using a Grignard in the presence of a free hydroxyl.

Personally, I would start by adding 1 eq PhMgBr to the lactone. At low T the intermediate hemiketal should be stable enough to slow a second addition to the product relative to the first addition. This is true for sugar lactones, for which single addition of MeMgBr works very well.

Next I would reduce with sodium borohydride.

The other obvious strategy is to reduce to the aldehyde first with DIBAL, then add Ph to the aldehyde. However, in this case the free hydroxyl may cause some problems with strongly basic reagents such as Grignards.
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