header

Showing posts with label Evan's Auxiliary. Show all posts
Showing posts with label Evan's Auxiliary. Show all posts

Friday, December 2, 2011

12/2/11 - Creation of the Evan's Auxiliary Enolate

    This reaction works much like the selectivity within amide enolate formation, where the enolate forms in the Z formation where the R group of the enolate is eclipsed by the carbonyl.  And this reaction here causes the Evans imide to form the Z enolate selectively due to the lithium metal being an oxophilic agent to both of the carbonyls there, making sure that the bond between the N and the alpha C of the carbonyl doesn't rotate.  Now this molecule is ready to be put to use in an enolate reaction.

Thursday, December 1, 2011

12/1/11 - Insertion of an Evan's Auxiliary on an enolizable carbonyl

   When performing reactions requiring specific stereochemical products (ie for biomedical purposes) it is necessary to gain these stereoisomers in very efficient ways.  One method of posing stereochemical controls is to introduce a very bulky group, adding steric interactions with the substrate and the reactant causing the reaction to add in a certain facial attack.  Over the next couple of days I will describe a certain reaction adhering to this method, and I will start here by describing how to create a stereochemically controlling reactant.  Here is the Evan's auxiliary, which adds to a acid chloride (of which we are wanting to enolize in the future) by the addition of a base (to deprotonate the Evan's auxiliary), and this case it is triethylamine.