Auto-Tandem Copper-Catalyzed Carboxylation of Undirected Alkenyl C-H Bonds with CO 2 by Harnessing β-Hydride Elimination.

The exploration into challenging scenarios of the application of elementary reactions offers excellent opportunities for the development of unique transformations under organometallic catalysis. As a ubiquitous reaction of metal alkyl complexes, β-hydride elimination plays a crucial role in a number of important catalytic transformations. However, its functions in these catalytic cycles are limited to either releasing alkene products or generating isomerized intermediates through further migratory insertion. Herein, we report that the precise manipulation of β-hydride elimination enables an auto-tandem copper catalysis for the carboxylation of undirected alkenyl C-H bonds with CO 2 . In this transformation, β-hydride elimination of an alkyl copper intermediate is facilitated, while its reaction with CO 2 is suppressed. The resulting copper hydride in turn reacts with CO 2 to provide access to a multitasking catalyst, which enables the tandem borylation/carboxylation of C-H bonds in two mechanistically distinct catalytic cycles.