C−H Bond Carboxylation with Carbon Dioxide

Carbon dioxide is a nontoxic, renewable, and abundant C1 source, whereas C-H bond functionalization represents one of the most important approaches to the construction of carbon-carbon bonds and carbon-heteroatom bonds in an atom- and step-economical manner. Combining the chemical transformation of CO2 with C-H bond functionalization is of great importance in the synthesis of carboxylic acids and their derivatives. The contents of this Review are organized according to the type of C-H bond involved in carboxylation. The primary types of C-H bonds are as follows: C(sp)-H bonds of terminal alkynes, C(sp2 )-H bonds of (hetero)arenes, vinylic C(sp2 )-H bonds, the ipso-C(sp2 )-H bonds of the diazo group, aldehyde C(sp2 )-H bonds, α-C(sp3 )-H bonds of the carbonyl group, γ-C(sp3 )-H bonds of the carbonyl group, C(sp3 )-H bonds adjacent to nitrogen atoms, C(sp3 )-H bonds of o-alkyl phenyl ketones, allylic C(sp3 )-H bonds, C(sp3 )-H bonds of methane, and C(sp3 )-H bonds of halogenated aliphatic hydrocarbons. In addition, multicomponent reactions, tandem reactions, and key theoretical studies related to the carboxylation of C-H bonds are briefly summarized. Transition-metal-free, organocatalytic, electrochemical, and light-driven methods are highlighted.