Dynamic processes in the copper-catalyzed substitution of chiral allylic acetates leading to loss of chiral information

摘要

Copper-catalyzed alpha-substitution of enantiomerically pure secondary allylic esters with Grignard reagents was studied with the aim to find conditions that give racemic products. it was observed that the degree of chiral transfer is strongly dependent on the temperature. The loss of chiral information is consistent with an equilibration of the Cu-III(allyl) intermediates prior to product formation. Equilibration of the reaction intermediates is of importance for a possible development of a dynamic kinetic asymmetric transformation (DYKAT) process, in which a chiral catalyst is used to produce an optically active product from a racemic substrate, by means of a dynamic equilibrium of the diastereomeric reaction intermediates.