Kinetic isotope effects 1,6-cuprate additions

ESR and CIDNP studies intended to detect the radical intermediates failed [63], Conjugate addition of a vinylcuprate reagent to an enone takes place with retention of the vinyl geometry indicating that no vinyl radical intermediate is involved [64, 65], Kinetic isotope effects and substituent effects in cuprate addition to benzophenone indicate that C-C bond formation is rate-determining, which is not consistent with the involvement of a radical ion pair intermediate [66]. 

Experimental and theoretical studies with 13C kinetic isotope effects have revealed that the C-C bond formation is the rate-determining step of the 1,6-cuprate additions to 2-en-4-ynoates.147 The reaction intermediates have been determined and the calculated activation barrier for the transition state was found to be in good agreement with the experimental value. 

The oxidation of cyano-Gilman cuprates has enabled the synthesis of new cyclophanes. Moreover, while BuhCuLi-LiCN has been reported to effect vinylallene formation by the 1,5-substitution of enyne acetates, it has been revealed that the application of Bu"3P to the reaction system considerably enhances the enantioselectivity of the synthesis. " Recent kinetic isotope studies into the chlorotrimethylsilane-mediated addition of lithiocuprates to cyclo-hexenone have suggested that reaction proceeds via an intermediate rr-com-plex. ... 

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