Highly Selective Metal Catalysts for Intermodular Carhenoid Insertion into Primary C-H Bonds and Enantioselective C-C Bond Formation

摘要

Direct functionalization of C—H bonds is an appealing strategy in organic synthesis but its practical application has so far been difficult to realize. The selective functionalization of primary C—H bonds of alkanes that also contain secondary and/or tertiary C-H bonds is a great challenge, as C-H bond energy follows an order primary > secondary > tertiary. In seminal works by Bergman, Jones, and their respective co-workers, stoichiometric reactions of alkanes with [Cp~*(Me3P)M] (Cp~* = C5Me5; M = Rh, Ir) resulted in the formation of C—M bonds by selective activation of primary C-H bonds. Subsequent work by Hartwig and coworkers demonstrated C—B bond formation by stoichiometric and catalytic functionalization of primary C-H bonds mediated by tungsten, rhodium, or ruthenium complexes. The high selectivity for primary C—H bond functionalization in these C-M or C-B bond-formation reactions (Scheme S1 in the Supporting Information) is considered to result from kinetic factors or steric interaction between the metal complexes and alkanes.