Copper(I)-Catalyzed Desulfinative Carboxylation of Sodium Sulfinates using Carbon Dioxide

Visible-Light-Promoted Cascade Carboxylation/Arylation of Unactivated Alkenes with CO2 for the Synthesis of Carboxylated Indole-Fused Heterocycles

Described here is a visible-light-promoted cascade carboxylation/arylation of indole-tethered unactivated alkenes with CO2 to access various carboxylated indole-fused heterocycles. This reaction is initiated by the addition of a CO2 radical anion to the alkene motif toward an alkyl carbon radical, followed by its addition to the aromatic ring, and then rearomatization to afford the final products. This reaction provides a facile and sustainable protocol for the construction of carboxylated indole-fused heterocycles using CO2 as the carboxylic source.

Recent trends in incorporation of CO2 into organosulfur compounds via C-S bond cleavage

Desulfurative functionalization of organosulfur compounds to form various carbon-carbon and carbon-heteroatom bonds has become established as a powerful tool in organic chemistry. In this context, desulfurative carboxylation of this class of compounds using carbon dioxide (CO2) as a sustainable and renewable source of carboxyl has recently been developed as an efficient option for the synthesis of carboxylic acid derivatives. The aim of this Focus Review is to summarize the major progress in this appealing research field with particular emphasis on the mechanistic features of the reactions. Literature has been surveyed until the end of February 2024, according to the data collected using SciFinder and Google Scholar engines.

Copper-Catalyzed C4-selective Carboxylation of Pyridines with CO2 via Pyridylphosphonium Salts

Pyridine motifs are widespread pharmacophores in many drugs. Installing various substituents through pyridine C-H bond functionalization is significant for new drug design and discovery. Developments of late-stage functionalization reactions enrich the strategies for selective functionalization of pyridines. However, late-stage C-H carboxylation of pyridines is a long-standing challenge, especially selectively carboxylation with CO2 on pyridine motifs. Herein, we describe a practical method for C4-H carboxylation of pyridines via one-pot C-H phosphination and copper-catalyzed carboxylation of the resulted phosphonium salts with CO2 . The reaction is conducted under mild conditions and compatible with multiple active groups and several pyridine drugs, providing diverse valuable isonicotinic acid compounds, demonstrating the application potential of this strategy.

Visible-Light Photoredox-Catalyzed Intermolecular α-Aminomethyl/Carboxylative Dearomatization of Indoles with CO2 and α-Aminoalkyl Radical Precursors

Disclosed here is a visible-light photoredox-catalyzed intermolecular sequential α-aminomethyl/carboxylative dearomatization of indoles with CO2 and α-aminoalkyl radical precursors, affording a series of functionalized indoline-3-carboxylic acids and lactams in good yields with high regioselectivity. This multicomponent reaction provides a green and facile method for the synthesis of diverse functionalized indolines by using CO2 as the carboxylic and carbonyl source.

Carboxylation of sodium arylsulfinates with CO2 over mesoporous K-Cu-20TiO2

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide. The catalyst showed excellent selectivity and good functional group tolerance to carboxylation recycle. The oxidation state of active copper(i) by characterization using FTIR, XRD, TG, XPS and TEM techniques proved to be efficacious to conduct atom economical reactions.

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide.

Visible-Light Photoredox-Catalyzed Dicarbofunctionalization of Styrenes with Oxime Esters and CO2: Multicomponent Reactions toward Cyanocarboxylic Acids and γ-Keto Acids

A photoredox-catalyzed dicarbofunctionalization of styrenes with oxime esters and CO₂ has been achieved. Notably, a series of four-, five-, or six-membered cyclic ketone oximes worked well to furnish a wide range of ε-, ζ-, and η-cyanocarboxylic acids in good yields. Furthermore, a series of γ-keto acids also could be obtained by employing acyclic ketone oxime esters as the carbonyl radical precursor. It provides convergent access to diverse biologically important cyanocarboxylic and γ-keto acids.

Photoredox-Catalyzed α-Aminomethyl Carboxylation of Styrenes with Sodium Glycinates: Synthesis of γ-Amino Acids and γ-Lactams

A visible-light photoredox-catalyzed reductive α-aminomethyl carboxylation of styrenes with sodium glycinates and CO₂ has been developed to synthesize a series of α,α-disubstituted γ-amino acids and γ-lactams with high efficiency and regioselectivity. Notably, CO₂ released from the decarboxylation step can be reused for the subsequent carboxylation. Distinct from the previous reactions with the same type of substrates leading to simple decarboxylation and olefin hydroalkylation, this process involves additional CO₂ sequestration, thus leading to olefin α-aminomethyl carboxylation. These findings not only provide new access to α,α-disubstituted γ-amino acids and γ-lactams but also serve as a proof of concept for CO₂ reutilization in decarboxylation reactions.

Transition-metal mediated carbon-sulfur bond activation and transformations: an update

Carbon-sulfur bond cross-coupling has become more and more attractive as an alternative protocol to establish carbon-carbon and carbon-heteroatom bonds. Diverse transformations through transition-metal-catalyzed C-S bond activation and cleavage have recently been developed. This review summarizes the advances in transition-metal-catalyzed cross-coupling via carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review on the same topic published in early 2013 (Chem. Soc. Rev., 2013, 42, 599-621), which is presented by the categories of organosulfur compounds, that is, thioesters, thioethers including heteroaryl, aryl, vinyl, alkyl, and alkynyl sulfides, ketene dithioacetals, sulfoxides including DMSO, sulfones, sulfonyl chlorides, sulfinates, thiocyanates, sulfonium salts, sulfonyl hydrazides, sulfonates, thiophene-based compounds, and C[double bond, length as m-dash]S functionality-bearing compounds such as thioureas, thioamides, and carbon disulfide, as well as the mechanistic insights. An overview of C-S bond cleavage reactions with stoichiometric transition-metal reagents is briefly given. Theoretical studies on the reactivity of carbon-sulfur bonds by DFT calculations are also discussed.

Palladium/copper-catalyzed multicomponent reactions of propargylic amides, halohydrocarbons and CO2 toward functionalized oxazolidine-2,4-diones

A palladium/copper-catalyzed oxy-carbonation of propargylic amides by halohydrocarbons and CO2 has been developed toward functionalized oxazolidine-2,4-diones. This multi-component reaction (MCR) was triggered by the oxidative addition of RX to Pd(0), followed by the sequential carboxylation of amide and trans-oxopalladation of an electron-deficient triple bond by RPdX species. Finally, the reductive elimination afforded products possessing tetra-substituted vinyl motifs and Pd(0). This protocol features simultaneous formation of three bonds, representing an efficient method for incorporation of CO2 into value-added heterocycles.

New trends and applications in carboxylation for isotope chemistry

Carboxylations are an important method for the incorporation of isotopically labeled ¹⁴CO₂ into molecules. This manuscript will review labeled carboxylations since 2010 and will present a perspective on the potential of recent unlabeled methodology for labeled carboxylations. The perspective portion of the manuscript is broken into 3 major sections based on product type, arylcarboxylic acids, benzylcarboxylic acids, and alkyl carboxylic acids, and each of those sections is further subdivided by substrate.

Regiocontrolled Synthesis of α-Sulfonylmethyl o-Nitrostyrenes via ZnI2-Mediated Sulfonylation and AgNO2/Pd(PPh3)4-Promoted o-Nitration

We report herein the AgNO₂/Pd(PPh₃)₄-promoted regiocontrolled o-nitration of α-sulfonylmethylstyrenes in MeNO₂ with good yields. The o-nitration process provides a series of sulfonyl o-nitrostyrenes. Substituted α-sulfonylmethylstyrenes were synthesized from ZnI₂-mediated sulfonylation of substituted α-methylstyrenes and sodium sulfinates (RSO₂Na) in MeCN with good to excellent yields. The structures of the key products were confirmed by X-ray crystallography. A plausible mechanism has been proposed herein.

Copper-catalyzed carboxylation reactions using carbon dioxide

Carbon dioxide (CO2), as a waste of manufacture, is a cheap and abundant C1 source. Utilization of CO2 for synthesis of carboxylic acids has been developed. Transition-metal complexes play a key role in catalytic carboxylation reactions employing CO2. This review summarizes recent advances in copper-catalyzed carboxylation reactions using CO2. The contents are arranged based on various substrates: organometallic reagents, aryl iodides, sodium sulfinates, terminal alkynes, arenes, heteroarenes, and unsaturated substrates.

A radical coupling reaction of DMSO with sodium arylsulfinates in air : mild utilization of DMSO as C1 resource for the synthesis of arylsulfonyl dibromomethane

A radical coupling reaction of DMSO with ArSO₂Na without the needs of anaerobic atmosphere to afford ArSO₂CHBr₂ is described.