Stereoselective_transformations

Stereoselective_transformations - Reisman, 242a...

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Stereoselective Reactions The Nomenclature: A b s o l u t e C o n f i g u r a t i o n: the spatial arrangement of the atoms of a chiral molecular entity as described by its Cahn-Ingold-Prelog stereochemical assignments (i.e. R or S). vs. R e l a t i v e C o n f i g u r a t i o n: the configuration of any stereochemical element with respect to any other stereochemical element in the same molecule. (R) OH OH (S) HO HO absolute configuration = ( R,R ) – these two molecules are enantiomers, they have opposite absolute configurations – these two molecules are diastereomers; they differ in the relative configurations of their stereogenic centers. Enantioselective Reactions: Reagent Controlled An Example: – This is an example of a catalytic enantioselective reaction; the chiral reagent is used in catalytic quantities. – In this example, the reagent discriminates between enantiotopic faces of the alkene. – For enantioselective reactions of prochiral substrates, opposite enantiomers of the chiral reagent or catalyst a l w a y s provide opposite enantiomers of the product with the same magnitude ee!
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This note was uploaded on 01/03/2012 for the course CH 242a taught by Professor List during the Fall '10 term at Caltech.

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Stereoselective_transformations - Reisman, 242a...

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