Artem Kireev - Selectivity Guidelines and a Reductive Elimination-Based Model for Predicting the Stereochemical Course of Conjugate Addition Reactions of Organocuprates to γ-Alkoxy-α,β-enoates

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      Publication Details (including relevant citation   information):

      J. Org. Chem. 2006, 71, 2630


      Current models used to predict the stereochemical outcome   of  organocopper conjugate addition processes focus on the   nucleophilic  addition step as stereochemistry-determining.   Recent kinetic, NMR,  kinetic isotope effect, and   theoretical density functional studies  strongly support the   proposal that stereochemical preferences in these  processes   are dictated by the reductive elimination step,   transforming  CuIII to CuI  intermediates. A new model that  considers various steric   and stereoelectronic factors involved in the  transition   state of the reductive elimination step is proposed and   then  used to interpret the results of systematic studies of   arylcuprate  conjugate addition reactions with cis and trans   γ-alkoxy-α,β-enoates.  The results give rise to the   following selectivity guidelines for this  process. To   achieve high anti-addition diastereoselectivities the use   of  trans esters with a bulky nonalkoxy substituent at the   γ-position is  recommended. While stereoelectronics disfavor   syn-addition, a judicious  choice of properly sized   γ-substituents may lead to the predominant  formation of   syn-products, especially with cis enoates. However, high    syn-selelectivities may be achieved by using γ-amino-α,β-enoates.

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