Transition metal–catalyzed alkyl-alkyl bond formation: Another dimension in cross-coupling chemistry

Because the backbone of most organic molecules is composed primarily of carbon-carbon bonds, the development of efficient methods for their construction is one of the central challenges of organic synthesis. Transition metal-catalyzed cross-coupling reactions between organic electrophiles and nucleophiles serve as particularly powerful tools for achieving carbon-carbon bond formation. Until recently, the vast majority of cross-coupling processes had used either aryl or alkenyl electrophiles as one of the coupling partners. In the past 15 years, versatile new methods have been developed that effect cross-couplings of an array of alkyl electrophiles, thereby greatly expanding the diversity of target molecules that are readily accessible. The ability to couple alkyl electrophiles opens the door to a stereochemical dimension-specifically, enantioconvergent couplings of racemic electrophiles-that substantially enhances the already remarkable utility of cross-coupling processes.