Palladium-Catalyzed Carbonylation of Aryl Bromides with Carbon Dioxide To Access Aryl Carboxylic Acids under Mild Conditions

Heterogeneous Catalytic Oxidations with In Situ-Generated Hypervalent Iodine-Based Porous Organic Polymers

Porous organic polymers (POPs) are novel emergent materials for heterogeneous organocatalysis owing to their remarkable physicochemical stabilities. Through a bottom-up approach entailing diligent design of twisted biaryl building blocks with in-built o-iodobenzoic acid (IA) moieties, a series of POP precatalysts, p-OMeIA-POP, DiMeIA-POP, and m-OMeIA-POP, were synthesized by employing Friedel-Crafts alkylation. These IA-POP precatalysts can undergo in situ oxidation in the presence of Oxone® to generate hypervalent iodine(V) species (λ5-iodanes), in particular, modified o-iodoxybenzoic acid, popularly termed IBX, which mediates diverse oxidative transformations. The applications of m-OMeIA-POP as a heterogeneous precatalyst in the presence of Oxone® are demonstrated for facile oxidation of i) primary and secondary alcohols to carbonyl compounds, ii) cleavage of olefins, vicinal diols, and acyloins into carboxylic acids and iii) oxidation of diols to lactones; the in situ formation of the λ5-iodane species in catalytic amounts precludes potential explosive attributes of IBX. It is shown that the IA-precatalyst (m-OMeIA-POP) can be easily recycled without any loss of catalytic activity. The results constitute the first demonstration of the development of IA-bearing POP precatalysts for in situ generation of hypervalent iodine(V) species and various heterogeneous oxidations mediated therefrom.

CO2 Fixation into Useful Aromatic Carboxylic Acids via C (sp2)-X Bonds Functionalization

Carbon dioxide (CO2) is an abundant and readily available carbon source. Its transformation into high-added-value chemicals is a beneficial strategy, which mitigates greenhouse gas emissions and provides new raw material sources for the chemical industry. Among these chemicals, the aromatic carboxylic acids and derivatives have broad applications in medicine, pesticides, and materials science. Therefore, the carboxylation of C(sp2)-X (X = metal, halide, H, O, or S) bonds with CO2 to efficiently construct aromatic carboxylic acids and their derivatives is a synthetic strategy of significance. This review highlights the recent progress in constructing carboxylic acids and derivatives through the carboxylation of C(sp2)-X bonds with CO2 including literature published from 2000 to December 2024.

Transition Metal-Free Direct Electrochemical Carboxylation of Organic Halides Using a Sacrificial Magnesium Anode: Straightforward Synthesis of Carboxylic Acids

The direct electrochemical carboxylation of aryl, benzyl and alkyl halides by CO2 is described using a magnesium anode and a nickel foam cathode in an undivided cell. The process employs a sacrificial anode and does not require the additional use of a transition metal catalyst or demanding conditions, as the reactions are carried out under galvanostatic mode, at -10 °C and with commercial DMF. Under these operationally simple conditions, an important range of carboxylic acids are affordable. Mechanistic investigation account for the in situ generation of a carbanionic species that is not a simple organomagnesium halide.

Silver-Catalyzed Coupling of Ethynylbenziodoxolones with CO2 and Amines to Afford O-β-Oxoalkyl Carbamates

A novel three-component coupling reaction of ethynylbenziodoxolones (EBXs) with CO2 and amines has been achieved via silver catalysis, thereby providing an efficient method for the construction of a range of structurally diverse and valuable O-β-oxoalkyl carbamates. The transformation proceeds under mild reaction conditions and exhibits a wide substrate scope and good functional group compatibility. In addition, this strategy could be extended to the synthesis of α-acyloxyketones using carboxylic acids as the nucleophiles to react with EBXs.

Et2 Zn-Mediated Gem-Dicarboxylation of Cyclopropanols with CO2

An unprecedented Et2 Zn-mediated gem-dicarboxylation of C─C/C─H single bond of cyclopropanols with CO2 is disclosed, which provides a straightforward and efficient methodology for the synthesis of a variety of structurally diverse and useful malonic acids in moderate to excellent yields. The protocol features mild reaction conditions, excellent functional group compatibility, broad substrate scope, and facile derivatization of the products. DFT calculations confirm that the transition-metal-free transformation proceeds through a novel ring-opening/α-functionalization/ring-closing/ring-opening/β-functionalization (ROFCOF) process, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) plays dual important roles in the transformation.