C−H Carboxylation of Aromatic Compounds through CO₂ Fixation

Abstract

Carbon dioxide (CO2) represents the most abundant and accessible carbon source on Earth. Thus the ability to transform CO2 into valuable commodity chemicals through the construction of C−C bonds is an invaluable strategy. Carboxylic acids and derivatives, the main products obtained by carboxylation of carbon nucleophiles by reaction of CO2, have wide application in pharmaceuticals and advanced materials. Among the variety of carboxylation methods currently available, the direct carboxylation of C−H bonds with CO2 has attracted much attention owing to advantages from a step‐ and atom‐economical point of view. In particular, the prevalence of (hetero)aromatic carboxylic acids and derivatives among biologically active compounds has led to significant interest in the development of methods for their direct carboxylation from CO2. Herein, the latest achievements in the area of direct C−H carboxylation of (hetero)aromatic compounds with CO2 will be discussed.

Carboxylation of Toluene with CO2‐derived Dimethyl Carbonate over Amorphous Ti−Zr Mixed‐metal Oxide Catalysts

“…They are produced commonly from petroleum‐based arenes via complex routes in current chemical industry . In comparison with conventional routes, the carboxylation of arenes with CO 2 is a convenient and environmentally friendly process for the synthesis of these carboxylic acids or derivates (Scheme a) . However, thermodynamically, it is not favorable for the carboxylation of arenes with CO 2 under standard reaction conditions (ΔG ∼50 kJ/mol).…”

“…[4] In comparison with conventional routes, the carboxylation of arenes with CO 2 is a convenient and environmentally friendly process for the synthesis of these carboxylic acids or derivates (Scheme 1a). [5] However, thermodynamically, it is not favorable for the carboxylation of arenes with CO 2 under standard reaction conditions (ΔG~50 kJ/mol). Hence, to date, the carboxylation reaction was still not achieved well, although many efforts have been made.…”

Supported Porous Nanomaterials as Efficient Heterogeneous Catalysts for CO2 Fixation Reactions

“…Highly reactive organometallic reagents like organolithium, Grignard, organoboron, organozinc, organotin, or even moderately reactive aryl halides can undergo direct carboxylation reaction in the presence of CO 2 and suitable metal catalysts for the synthesis of benzoic acids, in which new C−C bond formation occurs under mild reaction conditions. In this context, Luo and Larrosa have reported the direct C−H carboxylation of a series of hetero aromatic compounds at moderately low reaction temperatures and ambient CO 2 pressure in the presence of Lewis acids/bases, organocatalysts, enzymes, or transition metals like Au, Cu, or Rh . These transition metals facilitate chelation‐assisted C−H activation followed by the insertion of CO 2 , whereas strong base could deprotonate the reactive C−H to generate a nucleophilic carbon atom that can attack the electrophilic CO 2 molecule to form the respective carboxylated heteroaromatics.…”

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

“…Excellent reviews on this topic have appeared recently [19,54,55,115]. Direct carboxylation of alkenyl-C-H bonds is more difficult to achieve, therefore, to the best of our knowledge, only one report from Iwasawa [116] describes direct carboxylation with CO 2 of 2-hydroxystyrenes in the presence of the Pd(acac) 2 /Cs 2 CO 3 catalytic system (Scheme 37).…”