Direct Carboxylation of C(sp3)-H and C(sp2)-H Bonds with CO2 by Transition-Metal-Catalyzed and Base-Mediated Reactions

Abstract

This review focuses on recent advances in the field of direct carboxylation reactions of C(sp 3 )-H and C(sp 2 )-H bonds using CO 2 encompassing both transition-metal-catalysis and base-mediated approach. The review is not intended to be comprehensive, but aims to analyze representative examples from the literature, including transition-metal catalyzed carboxylation of benzylic and allylic C(sp 3 )-H functionalities using CO 2 which is at a "nascent stage". Examples of light-driven carboxylation reactions of unactivated C(sp 3 )-H bonds are also considered. Concerning C(sp 3 )-H and C(sp 2 )-H deprotonation reactions mediated by bases with subsequent carboxylation of the carbon nucleophile, few examples of catalytic processes are reported in the literature. In spite of this, several examples of base-promoted reactions integrating "base recycling" or "base regeneration (through electrosynthesis)" steps have been reported. Representative examples of synthetically efficient, base-promoted processes are included in the review.

C−H Bond Carboxylation with Carbon Dioxide

“…For example, C−H carboxylation of aromatic compounds through CO 2 fixation has been reviewed recently . The direct carboxylation of C(sp 3 )−H and C(sp 2 )−H bonds with CO 2 by transition‐metal‐catalyzed and base‐mediated reactions has also been surveyed . However, some important aspects, including several specific types of C−H carboxylation reactions, transition‐metal‐free reactions (including Lewis acid mediated reactions), multicomponent reactions, tandem reactions, and key theoretical studies related to the carboxylation of C−H bonds, are overlooked.…”

Enantioselective CO2 Fixation Via a Heck‐Coupling/Carboxylation Cascade Catalyzed by Nickel

“…Over the past decade, incredible steps towards the chemoselective catalytic electrophilic as well as nucleophilic activation of CO 2 have been taken, making the selective incorporation of CO 2 in organic scaffolds accessible in synthetically useful manners. [2] In organic synthesis, catalytic carboxylation [3] and carbonylation [4] protocols, based on a low-pressure CO 2 atmosphere, represent important cornerstones in the creation of chemical complexity/diversity via C1-homologation reactions. However, despite the titanic efforts deployed in this direction by means of metal-based and metal-free catalysis, the realization of added-value compounds via enantioselective CO 2 -based catalytic carboxylation reactions is still far from being fully developed.…”

CO2 + Light: “Green” Valorization of Simple Arenes and Styrenes

“…To overcome these limitations, significant efforts have been devoted over the last decade to uncovering alternative strategies for C-H carboxylation by using CO 2 as the carboxylating agent. [1][2][3] Accordingly, catalytic transformations using Au, Cu, and Rh catalysts have been designed. In parallel, dual catalysis merging metal catalysis and photocatalysis has turned out to be an interesting alternative for direct carbonylation, although excess of a sacrificial electron donor is needed to complete the catalytic system.…”