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.

We describe an operationally simple transition-metal-free borylation of alkyl iodides. This method uses commercially available diboron reagents as the boron source and exhibits excellent functional group compatibility. Furthermore, a diverse range of primary and secondary alkyl iodides could be effectively transformed to the corresponding alkylboronates in excellent yield. Mechanistic investigations suggest that this borylation reaction proceeds through a single-electron transfer mechanism featuring the generation of an alkyl radical intermediate.

An anodic oxidation/cyclization of 2-arylbenzoic acids for the synthesis of dibenzopyranones has been developed. The reaction proceeds at room temperature with no oxidant or electrolyte required and exhibits a high atom economy with H being the only byproduct. A series of dibenzopyranones was obtained in good to excellent yields. Urolithins A, B, and C are formally synthesized by adopting this method as a key step to demonstrate its synthetic utility.

Summary of main observation and conclusion Herein, we report the first electrochemical strategy for the borylation of aryl iodides via a radical pathway using current as a driving force. A mild reaction condition allows an assorted range of readily available aryl iodides to be proficiently converted into synthetically valuable arylboronic esters under transition metal catalyst‐free conditions. Moreover, this method also shows good functional group tolerance. Initial control mechanistic experiments reveal the formation of aryl radical as a key intermediate and the current plays an important role in the generation of radical intermediate.

A copper/N-heterocyclic carbene (NHC) catalysed carboxylation of aryl boronic acids under one atmospheric pressure of CO2 has been developed.

The first catalytic enantioselective C(sp)―C(sp3) cross‐coupling reaction between N‐tosylhydrazones and trialkylsilylethynes in the presence of Cu(I) salts and chiral phosphoramidite ligands was developed. A series of synthetically interesting, functionalized alkynes were obtained with moderate to good enantioselectivities (up to 83% ee). Cu(II) carbene migratory insertion is proposed to be the enantio‐determining step.

The electrolysis of organic acids has garnered increasing attention in recent years. In addition to the famous electrochemical decarboxylation known as Kolbe electrolysis, a number of other electrochemical processes have been recently established that allow for the construction of carbon–heteroatom and sulfur–heteroatom bonds from organic acids. Herein, recent advances in electrochemical C−X and S−X (X=N, O, S, Se) bond‐forming reactions from five classes of organic acids and their conjugate bases, namely, carboxylic, thiocarboxylic, phosphonic, sulfinic, and sulfonic acids, are surveyed.

A cuprous halide catalysed carboxylation of alkenyl boronic acids and alkenyl boronic acid pinacol esters under CO 2 , affording the corresponding α, -unsaturated carboxylic acids in good yield, has been developed. The potassium (E)- [a] . The current research interests of his group include CO 2 utilization in organic synthesis, organic electrochemistry, and modification of semiconductor oxides for energy and resource utilization.Scheme 2. The reaction of (E)-styrylboronic acid 1a, (E)-4,4,5,5-tetramethyl-2-styryl-1,3,2-dioxaborolane 3a, (E)-trifluoro(styryl)borate 4 with CO 2 in the optimal conditions. a Isolated yield. acid and p-methoxy substituted styrylboronic acid provided lower yields (56 %, 2c and 64 %, 2d), probably because electronic effect promoted the generation of protodeboronation Scheme 3. The substrates scope of alkenyl boron acids. Reactions were carried out by using alkenyl boronic acid 1 (1.0 mmol), cat. CuCl (3.0 mol %), base KOMe (2.0 equiv.) in DMA at 70°C for 24 h under 1 atm CO 2 . Isolated yields were reported.