October 17, 2019, 03:03:57 PM
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Topic: Enolates formation  (Read 171 times)

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Offline xshadow

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Enolates formation
« on: July 18, 2019, 02:56:57 PM »
Hi!
Can I use RO- in order to create an enolate?

Because I've seen using it somewhere ...but RO- can:

- deprotonate C-H   in α position to C=O (enolate ion formation)

-  can attack the C=O of a keton giving a R1-C-(OH)R2
Or an ester (ester -OR go away and we have carboxylic acid)


So I think is better using LDA ,that is bulky and more basic..mpr if we want an RO- base we should use Tert-butoxy??

Is it correct?
Thanks!!!!!


Offline hollytara

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Re: Enolates formation
« Reply #1 on: July 18, 2019, 04:16:13 PM »
It depends. 

If it is an enolate based reaction that uses an ester - like a Claisen condensation or malonic ester reaction - you can use the alkoxide that is the same as the ester - then if their is any reaction at the ester the product is the same as the reactant.  Use ethoxide for ethyl esters, methoxide for methyl esters, and so on.  The side reaction might happen, but it won't matter.

For other carbonyls, the alkoxide of choice is t-butoxide for the same reason - bulky and won't react as nucleophile with ketones.  Sodium T-butoxide is a little easier to handle than LDA, and probably cheaper.

Offline xshadow

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Re: Enolates formation
« Reply #2 on: July 19, 2019, 02:32:09 AM »
Don't have thought about this thing on claisen condensation

Thanks  :)


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