Acceptor/Acceptor-Substituted Diazo Reagents for Carbene Transfers: Cobalt-Catalyzed Asymmetric Z-Cyclopropanation of Alkenes with α-Nitrodiazoacetates

摘要

Cyclopropanes are an important class of compounds that have numerous fundamental and practical applications. One of the most general approaches for the stereoselective construction of cyclopropanes, which are the smallest all-carbon cyclic molecules, is the metal-catalyzed asymmetric cyclopropana-tion of alkenes with diazo reagents. Among the three classes of common diazo reagents, acceptor-substituted diazo reagents, such as diazoesters, are well established as the most effective carbene sources for metal-catalyzed stereoselective cyclopropanation. There has been great progress in metal-catalyzed selective carbene transfers with donor/ acceptor-substituted diazo reagents such as vinyldiazoesters and aryldiazoesters.However, asymmetric cyclopropanation with acceptor/acceptor-substituted diazo reagents remains a major challenge in the field because of their inherent low reactivity and perceived poor enantioselectiv-ity. Therefore, more reactive and enantiodiscriminating catalysts need to be developed to meet this challenge.