Using carbon dioxide as a building block in organic synthesis

Controllable Active Intermediate in CO2 Hydrogenation Enabling Highly Selective N,N-Dimethylformamide Synthesis via N-Formylation

N,N-Dimethylformamide (DMF) is a widely used solvent, and its green and low-carbon synthesis methods are in high demand. Herein, we report a new approach for DMF synthesis using a continuous flow reaction system with a fixed-bed reactor and a ZnO-TiO2 solid solution catalyst. This catalyst effectively utilizes CO2, H2, and dimethylamine (DMA) as feedstocks, demonstrating performance with 99% DMF selectivity and single-pass DMA conversion approaching thermodynamic equilibrium. Moreover, the catalyst demonstrates good stability, with no signs of deactivation over 1000 h of continuous operation. The key to superior activity lies in the synergetic effect of the Zn and Ti sites, which facilitates the formation of active formate species. These species act as crucial intermediates, reacting with DMA to produce DMF. Importantly, the slow hydrogenation kinetics of the formate species prevent the formation of CH2O* species, thereby suppressing the formation of the undesired byproduct, trimethylamine. This work underscores the potential of kinetically controlling active intermediates in CO2 hydrogenation to prepare high-value-added chemicals by coupling them to platform molecules. It presents a promising strategy for the efficient utilization of CO2 resources and offers a valuable solution for large-scale DMF synthesis.

Electrochemical Dicarboxylation of Vinyl Epoxide with CO2 for the Facile and Selective Synthesis of Diacids

We present a novel electrochemical dicarboxylation of epoxides with CO2, characterized by the cleavage of two C-O single bonds. Not only are vinyl epoxides viable, but cyclic carbonates also serve as effective substrates, facilitating the synthesis of E-configured adipic and octanedioic acids with high chemo-, regio-, and stereoselectivity. The synthetic practicality is further highlighted by the diverse functionalizations of the resulting multifunctional diacids. Mechanistic studies support the single-electron transfer reduction of CO2 to its radical anion, which undergoes radical addition to the vinyl moiety of epoxides. The subsequent reductive cleavage of two C-O bonds, coupled with a nucleophilic attack on CO2, culminates in the formation of the desired diacid products.

Electrochemical Cyclizative Carboxylation of Alkene-Tethered Aryl Isocyanides with Carbon Dioxide

Herein, we present an unprecedented electrochemical reductive cyclizative carboxylation of o-vinylphenyl isocyanides with carbon dioxide achieved without the use of metal catalysts. This protocol demonstrates a broad substrate scope and good functional group tolerance, facilitating the rapid assembly of 2-oxoindolin-3-acetic acids in good to high yields with excellent regioselectivity. Furthermore, these structural motifs may have potential applications in formal synthesis of bioactive natural products.

Heteroannulations of cyanoacetamide-based MCR scaffolds utilizing formamide

C1 chemistry has a central role in the efficient utilization of single-carbon molecules, contributing significantly to sustainability, innovation and economic growth across various sectors. In this study, we present an efficient and rapid method for synthesizing a variety of heteroannulated pyrimidones using cyanoacetamide-based multicomponent reaction (MCR) chemistry. By utilizing specific MCR-based scaffolds as precursors and employing the abundant and inexpensive formamide as a C1 feedstock under neat conditions, we were able to efficiently access substituted thieno-, quinolino- and indolopyrimidones without the need of column chromatography. Further, a single-crystal X-ray structure was obtained, revealing certain geometrical features.

Carboxylations of (Hetero)Aromatic C-H Bonds Using an Alkyl Silyl Carbonate Reagent

In this paper, we report that the use of an alkyl silyl carbonate reagent combined with CsF and 18-crown-6 facilitates efficient direct carboxylations of (hetero)aromatic C-H bonds. This system also enables benzylic carboxylation of a toluene derivative and double carboxylation of methyl heteroarene. The carbonate reagent is characterized by its ease of handling and storage. Moreover, we demonstrate the application of this system in 13C-labeling experiments.

Substrate-Controlled Divergent Reductive Cyclization of 2-Arylanilines Using CO2 as a Switching Reagent

Capturing CO2 is highly valued in the field of organic synthesis, especially underdeveloped dual-CO2 conversion. In this study, we detail a novel reductive cyclization of 2-indolylanilines with dual CO2 as a difunctional reagent in the presence of PMHS [poly(methylhydrosiloxane)], delivering methyl-substituted quinoxalines. Furthermore, another chemoselective cyclization with 2-pyrrolylanilines is also realized by converting mono-CO2. Mechanistic investigations shed light upon the fact that this substrate-controlled divergence mainly depends on the formation of N-diacylative intermediates.

CO2 Reduction at a Borane-Modified Iron Complex: A Secondary Coordination Sphere Strategy

This work addresses fundamental questions that deepen our understanding of secondary coordination sphere effects on carbon dioxide (CO2) reduction using derivatized hydride analogues of the type, [Cp*Fe(diphosphine)H] (Cp* = C5Me5 -) - a well-studied family of organometallic complex - as models. More precisely, we describe the general reactivity of [(Cp*-BR2)Fe(diphosphine)H], which contains an intramolecularly positioned Lewis acid, and its cooperative reactivity with CO2. Control experiments underscore the critical nature of borane incorporation for transforming CO2 to reduced products, a reaction that does not occur for unfunctionalized [Cp*Fe(diphosphine)H]. Additional experiments highlight relevance of borane hybridization and substituent effects. Mechanistic studies performed in the presence and absence of CO2 emphasize the significance of carbonyl substrate to catalyst longevity. Lessons from these reactions were also transferable - with such borane-containing complexes enabling the chemoselective reduction of aldehydes in the presence of alkenes. These findings provide valuable insights into metal-ligand cooperative design strategies for carbonyl reduction and illustrate the versatility of intramolecularly positioned Lewis acids for otherwise challenging chemical transformations.

Organocatalytic CS2 insertion into epoxides in neat conditions: a straightforward approach for the efficient synthesis of Di- and tri-thiocarbonates

The straightforward organocatalytic insertion of carbon disulfide (CS2) into epoxides using either choline chloride (ChCl) or tetrabutylammonium chloride (TBACl) is reported, for the first time, under solvent-free (neat) conditions. Fine-tuning of our system allowed us to obtain either dithiocarbonates (DTCs) or trithiocarbonates (TTCs) with high efficiency. Additionally, a mechanistic proposal is presented, supported by experimental evidence, DFT calculations and wavefunction analyses.

Synergistic Photoredox/Palladium Catalyzed Enantioconvergent Carboxylation of Racemic Heterobiaryl (Pseudo)Halides with CO2

Herein, we report a synergistic photoredox/palladium catalytic system for the efficient enantioconvergent synthesis of axially chiral esters from racemic heterobiaryl (pseudo)halides (bromides/triflates) with CO2 and alkyl bromides under mild conditions. A wide range of axially chiral esters were obtained in good to high yields with excellent enantioselectivities. Detailed mechanistic studies unveiled that the ratio of photocatalyst and palladium catalyst exhibited significant impact on the chemo- and enantioselectivities of the reaction. Kinetic studies and control experiments supported the proposed mechanism involving cascade asymmetric carboxylation followed by SN2 substitution. The achievement of high enantioselectivity relies not only on the choice of synergistic metallaphotoredox catalysts but also on the utilization of alkyl bromides, which trap the generated chiral carboxylic anions in situ, thus preventing their immediate racemization.

Nickel-Catalyzed Atroposelective Carbo-Carboxylation of Alkynes with CO2: En Route to Axially Chiral Carboxylic Acids

Precise synthesis of carboxylic acids via catalytic carboxylation with CO2 is highly appealing. Although considerable advancements have been achieved in difunctionalizing carboxylation of unsaturated hydrocarbons, the asymmetric variants are conspicuously underdeveloped, particularly in addressing axially chiral alkenes. Herein, we report the first catalytic atroposelective carboxylation of alkynes with CO2. A variety of valuable axially chiral carboxylic acids are obtained with good yields and high chemo-, regio-, Z/E and enantio-selectivities. Notably, an unexpected anti-selective carbo-carboxylation is observed in the sp2-hybrid carbo-electrophile-initiated reductive carboxylation of alkynes. Mechanistic studies including DFT calculation elucidate the origin of chiral induction and anti-selectivity in vinyl-carboxylation of alkynes.

Remote C(sp3)-H Carboxylation with CO2 via Visible-Light-Catalyzed 1,5-Hydrogen Atom Transfer

The direct carboxylation of C(sp3)-H bonds with CO2 represents a challenging but highly attractive strategy in organic synthesis. In this study, we presented a visible-light-catalyzed strategy for carboxylating remote C(sp3)-H bonds with CO2 via aryl radical induced 1,5-hydrogen atom transfer. This transformation involves generating alkyl radicals via 1,5-hydrogen atom transfer from aryl radicals, forming alkyl carbanions as key intermediates, and a subsequent nucleophilic attack with CO2, thereby enabling access to a variety of tertiary and quaternary carboxylic acids in moderate to good yields.

C(sp3)-H Carbonylative Cyclization of Hydrazones with CO2: Synthesis of Pyrazolone Derivatives

A novel method is reported to synthesize various pyrazolones through transition-metal-free and redox-neutral 1°, 2°, or 3° C(sp3)-H carbonylative cyclization using 1 atm of CO2 as a green carbonyl source, featuring good functional group tolerance, a broad substrate scope, facile scalability, and easy product transformation. The utility of this method could be demonstrated by the applications in preparing useful synthetic intermediates and bioactive compounds.

Fixation of CO2 with Epoxides Catalyzed by Pincer-Type Azo-Aromatic Complexes of Cobalt as Catalysts

Employing a series of azo-aromatic pincer-type cobalt(II) complexes, 1-5, and an imine-based cobalt complex, 6, a highly efficient catalytic protocol for the cycloaddition of CO2 with epoxides at low pressure of CO2 is reported. The electron-withdrawing group-substituted ligands containing complexes 2 and 4 were most efficient. The catalytic protocol with 2 involved a synergistic participation of an azo-aromatic catalyst (0.1 mol %) and tetra-butyl ammonium iodide (TBAI), a cocatalyst (0.2 mol %) at 90 °C temperature, and 1 bar CO2 pressure. A very good conversion, high turnover number, and reusability were observed. Complex 4 worked directly in the reaction, and its efficiency was similar to the efficiency of 2 and TBAI. As 2 was synthesized from a cheaper CoCl2, 2 showed to be more stable than 4; the combination of 2 and TBAI was used for a detailed study. The imine-based complex 6 was less efficient than the corresponding azo-aromatic complex 5. The catalytic protocol was versatile. It was also very effective for the full conversion of bis-epoxides to bis-carbonates at only 2 bar of CO2 pressure in 24 h. The reaction mechanism was investigated using various spectroscopic and computational studies.

Selecting a preculture strategy for improving biomass and astaxanthin productivity of Chromochloris zofingiensis

Chromochloris zofingiensis is a potential source of natural astaxanthin; however, its rapid growth and astaxanthin enrichment cannot be achieved simultaneously. This study established autotrophic, mixotrophic, and heterotrophic preculture patterns to assess their ameliorative effect on the C. zofingiensis heterotrophic growth state. In comparison, mixotrophic preculture (MP) exhibited the best improving effect on heterotrophic biomass concentration of C. zofingiensis (up to 121.5 g L-1) in a 20 L fermenter, reaching the global leading level. The astaxanthin productivity achieved 111 mg L-1 day-1, 7.4-fold higher than the best record. The transcriptome and 13C tracer-based metabolic flux analysis were used for mechanism inquiry. The results revealed that MP promoted carotenoid and lipid synthesis, and supported synthesis preference of low unsaturated fatty acids represented by C18:1 and C16:0. The MP group maintained the best astaxanthin productivity via mastering the balance between increasing glucose metabolism and inhibition of carotenoid synthesis. The MP strategy optimized the physiological state of C. zofingiensis and realized its heterotrophic high-density growth for an excellent astaxanthin yield on a pilot scale. This strategy exhibits great application potential in the microalgae-related industry. KEY POINTS: • Preculture strategies changed carbon flux and gene expression in C. zofingiensis • C. zofingiensis realized a high-density culture with MP and fed-batch culture (FBC) • Astaxanthin productivity achieved 0.111 g L-1 day-1 with MP and FBC.

Reductive Transformation of CO2 to Organic Compounds

Carbon dioxide is a major greenhouse gas and a safe, abundant, easily accessible, and renewable C1 resource that can be chemically converted into high value-added chemicals, fuels and materials. The preparation of urea, organic carbonates, salicylic acid, etc. from CO2 through non-reduction conversion has been used in industrial production, while CO2 reduction transformation has become a research hotspot in recent years due to its involvement in energy storage and product diversification. Designing suitable catalysts to achieve efficient and selective conversion of CO2 is crucial due to its thermodynamic stability and kinetic inertness. From this perspective, the redistribution of charges within CO2 molecules through the interaction of Lewis acid/base or metal complexes with CO2, or the forced transfer of electrons to CO2 through photo- or electrocatalysis, is a commonly used effective way to activate CO2. Based on understanding of the activation/reaction mechanism on a molecular level, we have developed metal complexes, metal salts, inorganic/organic salts, ionic liquids, as well as nitrogen rich and porous materials as efficient catalysts for CO2 reductive conversions. The goal of this personal account is to summarize the catalytic processes of CO2 reductive conversion that have been developed in the past 7 years: 1) For the reductive functionalization of CO2, the major challenge lies in accurately adjusting reaction parameters (such as pressure) to achieve high catalytic efficiency and the product selectivity; 2) For photocatalytic or electrocatalytic reduction of CO2, how to suppress competitive hydrogen evolution reactions and improve catalyst stability are key points that requires continuous attention.

Photo-induced carboxylation of C(sp2)-S bonds in aryl thiols and derivatives with CO2

Aryl thiols have proven to be a useful class of electron donors and hydrogen atom sources in photochemical processes. However, the direct activation and functionalization of C(sp2)-S bonds in aryl thiols remains elusive in the field of photochemistry. Herein, a photochemical carboxylation of C(sp2)-S bonds in aryl thiols with CO2 is reported, providing a synthetic route to important aryl carboxylic acids. Moreover, different kinds of aryl thiol derivatives, benzeneselenol and diphenyl diselenide also show moderate-to-high reactivity in this transformation. Mechanistic studies, including DFT calculations, suggest that the in situ generated carbon dioxide radical anion (CO2•-) and disulfide might be the key intermediates, which undergo radical substitution to yield products. This reaction features mild and catalyst-free conditions, good functional group tolerance and wide substrate scope. Furthermore, the efficient degradation of polyphenylene sulfide highlights the usefulness of this methodology.

Integrated Carbon Dioxide Capture by Amines and Conversion to Methane on Single-Atom Nickel Catalysts

Direct electrochemical reduction of carbon dioxide (CO2) capture species, i.e., carbamate and (bi)carbonate, can be promising for CO2 capture and conversion from point-source, where the energetically demanding stripping step is bypassed. Here, we describe a class of atomically dispersed nickel (Ni) catalysts electrodeposited on various electrode surfaces that are shown to directly convert captured CO2 to methane (CH4). A detailed study employing X-ray photoelectron spectroscopy (XPS) and electron microscopy (EM) indicate that highly dispersed Ni atoms are uniquely active for converting capture species to CH4, and the activity of single-atom Ni is confirmed using control experiments with a molecularly defined Ni phthalocyanine catalyst supported on carbon nanotubes. Comparing the kinetics of various capture solutions obtained from hydroxide, ammonia, primary, secondary, and tertiary amines provide evidence that carbamate, rather than (bi)carbonate and/or dissolved CO2, is primarily responsible for CH4 production. This conclusion is supported by 13C nuclear magnetic resonance (NMR) spectroscopy of capture solutions as well as control experiments comparing reaction selectivity with and without CO2 purging. These findings are understood with the help of density functional theory (DFT) calculations showing that single-atom nickel (Ni) dispersed on gold (Au) is active for the direct reduction of carbamate, producing CH4 as the primary product. This is the first example of direct electrochemical conversion of carbamate to CH4, and the mechanism of this process provides new insight on the potential for integrated capture and conversion of CO2 directly to hydrocarbons.

Fast, Regioselective Aminolysis of Tetrasubstituted Cyclic Carbonates and Application to Recyclable Thermoplastics and Thermosets

Herein, the long-standing challenge of the ring-opening aminolysis of CO2-derived tetrasubstituted cyclic carbonates at room temperature (r.T) is overcome under catalyst-free conditions. Molecular design of the cyclic carbonate by substitution of an alkyl group by a thioether unlocks quantitative conversion at r.T and ensures total regioselectivity toward highly substituted oxazolidone scaffolds. An in-depth rationalization of the high reactivity of these cyclic carbonate structures and of the aminolysis reaction mechanism is provided by a computational study supporting experimental observations. The high efficiency of the reaction is then translated to the deconstruction of high-performance thermoplastics containing tetrasubstituted cyclic carbonate linkages to deliver building blocks that are reused for designing recyclable thermosets bearing dynamic N,S-acetal linkages.

Single-Pass Demonstration of Integrated Capture and Catalytic Conversion of CO2 from Simulated Flue Gas to Methanol in a Water-Lean Carbon Capture Solvent

Here, we demonstrate an integrated semibatch simultaneous CO2 capture and conversion to methanol process using a water-lean solvent, N-(2-ethoxyethyl)-3-morpholinopropan-1-amine (2-EEMPA), that serves as both the capture solvent and subsequent condensed-phase medium for the catalytic hydrogenation of CO2. CO2 is captured from simulated coal-derived flue gas at a target >90 mol % capture efficiency, with a continuous slipstream of CO2-rich solvent delivered to a fixed bed catalytic reactor for catalytic hydrogenation. A single-pass conversion rate >60 C-mol % and selectivity >80 C-mol % are observed for methanol at relatively low temperatures (<200 °C) in the condensed phase of the carbon capture solvent. Hydrogenation products also include higher alcohols (e.g., ethanol and propanol) and hydrocarbons (e.g., methane and ethane), suggesting that multiple products could be made offering adaptability with varied CO2-derived products. Catalyst activity and selectivity are directly impacted by the water content in the capture solvent. Anhydrous operation provides high catalyst activity and productivity, suggesting that water management will be a critical parameter in real-world operation. Ultimately, we conclude that the integrated capture and catalytic hydrogenation of CO2 are chemically viable and potentially more energetically efficient and cost-effective than conventional separate capture and conversion approaches.

A chemoselective hydroxycarbonylation and 13C-labeling of aryl diazonium salts using formic acid as the C-1 source

We report a one-pot synthesis of aryl carboxylic acids utilizing HCOOH as a CO surrogate with low Pd-catalyst loading. This operationally simple and scalable method does not require use of a high-pressure reactor, two-chamber reaction vessel, phosphine ligand, or base and proceeds in a relatively short amount of time at ambient temperature. Notably, halides, including iodo and bromo groups, and nitro groups remain intact under these mild reaction conditions. This methodology has been successfully applied to synthesizing 13C-labeled aryl carboxylic acids with satisfactory yields.

Solvent Free Ambient Pressure CO2 Cycloaddition Catalyzed by Cobalt-Impregnated 2D-Nanofibrous COFs

Covalent organic frameworks (COFs) constitute an evolving class of permanently porous and ordered materials, and they have recently attracted increased interest due to their intriguing morphological features and numerous applications in gas storage, adsorption, and catalysis. However, their low aqueous stabilities and tedious syntheses generally hamper their use in heterogeneous catalysis. Nonetheless, a capable and water-stable heterogeneous catalytic system for coupling CO2/epoxides to generate industrially important cyclic carbonates is still of great interest. Herein, exceedingly water- and thermally stable 2D-cobalt-impregnated hydrazone-linked fibrous COFs are reported as a catalyst for CO2/epoxide coupling reactions at ambient pressure. The functionalized cobalt (Co)-doped COFs demonstrated excellent catalytic activities with the high TONs (80925) and TOFs (6466 h-1), outperforming reported heterogeneous catalysts for CO2/epoxide coupling at ambient pressure. We found that the Co2+ ions within the COF matrix catalyze CO2 cycloaddition through density functional theory calculations. We also confirmed the excellent structural stability and consistent activity of Co-doped COFs up to ten repeating cycles.

Evolution of Copolymers of Epoxides and CO2: Catalysts, Monomers, Architectures, and Applications

The copolymerization of CO2 and epoxides presents a transformative approach to converting greenhouse gases into aliphatic polycarbonates (CO2-PCs), thereby reducing the polymer industry's dependence on fossil resources. Over the past 50 years, a wide array of metallic catalysts, both heterogeneous and homogeneous, have been developed to achieve precise control over polymer selectivity, sequence, regio-, and stereoselectivity. This review details the evolution of metal-based catalysts, with a particular focus on the emergence of organoborane catalysts, and explores how these catalysts effectively address kinetic and thermodynamic challenges in CO2/epoxides copoly2merization. Advances in the synthesis of CO2-PCs with varied sequence and chain architectures through diverse polymerization protocols are examined, alongside the applications of functional CO2-PCs produced by incorporating different epoxides. The review also underscores the contributions of computational techniques to our understanding of copolymerization mechanisms and highlights recent advances in the closed-loop chemical recycling of CO2-sourced polycarbonates. Finally, the industrialization efforts of CO2-PCs are discussed, offering readers a comprehensive understanding of the evolution and future potential of epoxide copolymerization with CO2.

Shape-Selective Zeolites for Tandem CO2 Hydrogenation-Carbonylation Reactions

The valorization of carbon dioxide as a C1 building block in C-C bond forming reactions is a critical link on the road to carbon-circular chemistry. Activation of this inert molecule through reduction with H2 to carbon monoxide in the reverse water-gas shift (RWGS) reaction can be followed by a wide spectrum of consecutive carbonylation reactions, but the RWGS is severely equilibrium limited at the moderate temperatures of carbonylations. Here we successfully reconcile both reactions in one pot, while avoiding incompatibilities through a zeolite-based compartmentalized approach. More specifically, Pt encapsulated in a small-pore LTA zeolite selectively generates carbon monoxide in mild reaction conditions; an ensuing one-pot carbonylation reaction allows to shift the equilibrium through continuous consumption of CO. Moreover, the zeolite encapsulation avoids undesired reactions like hydrogenation of the olefin reactant through a molecular sieving effect. This strategy was first studied in-depth for Rh-catalyzed olefin hydroformylation with CO2/H2, affording aldehydes in good yields with high regioselectivities. The methodology was then extended to a variety of carbonylations using CO2 for the synthesis of bulk and fine chemicals.

Taming CO2•- via Synergistic Triple Catalysis in Anti-Markovnikov Hydrocarboxylation of Alkenes

The direct utilization of carbon dioxide as an ideal one-carbon source in value-added chemical synthesis has garnered significant attention from the standpoint of global sustainability. In this regard, the photo/electrochemical reduction of CO2 into useful fuels and chemical feedstocks could offer a great promise for the transition to a carbon-neutral economy. However, challenges in product selectivity continue to limit the practical application of these systems. A robust and general method for the conversion of CO2 to the polarity-reversed carbon dioxide radical anion, a C1 synthon, is critical for the successful valorization of CO2 to selective carboxylation reactions. We demonstrate herein a hydride and hydrogen atom transfer synergy driven general catalytic platform involving CO2•- for highly selective anti-Markovnikov hydrocarboxylation of alkenes via triple photoredox, hydride, and hydrogen atom transfer catalysis. Mechanistic studies suggest that the synergistic operation of the triple catalytic cycle ensures a low-steady-state concentration of CO2•- in the reaction medium. This method using a renewable light energy source is mild, robust, selective, and capable of accommodating a wide range of activated and unactivated alkenes. The highly selective nature of the transformation has been revealed through the synthesis of hydrocarboxylic acids from the substrates bearing a hydrogen atom available for intramolecular 1,n-HAT process as well as diastereoselective synthesis. This technology represents a general strategy for the merger of in situ formate generation with a synergistic photoredox and HAA catalytic cycle to provide CO2•- for selective chemical transformations.

Conversion of Carbon Dioxide into Molecular-based Porous Frameworks

ConspectusThe conversion of carbon dioxide (CO2) to value-added functional materials is a major challenge in realizing a carbon-neutral society. Although CO2 is an attractive renewable carbon resource with high natural abundance, its chemical inertness has made the conversion of CO2 into materials with the desired structures and functionality difficult. Molecular-based porous materials, such as metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), are designable porous solids constructed from molecular-based building units. While MOF/COFs attract wide attention as functional porous materials, the synthetic methods to convert CO2 into MOF/COFs have been unexplored due to the lack of synthetic guidelines for converting CO2 into molecular-based building units.In this Account, we describe state-of-the-art studies on the conversion of CO2 into MOF/COFs. First, we outline the key design principles of CO2-derived molecular building units for the construction of porous structures. The appropriate design of reactivity and the positioning of bridging sites in CO2-derived molecular building units is essential for constructing CO2-derived MOF/COFs with desired structures and properties. The synthesis of CO2-derived MOF/COFs involves both the transformation of CO2 into building units and the formation of extended structures of the MOF/COFs. We categorized the synthetic methods into three types as follows: a one-step synthesis (Type-I); a one-pot synthesis without workup (Type-II); and a multistep synthesis which needs workup (Type-III).We demonstrate that borohydride can convert CO2 into formate and formylhydroborate that serve as a bridging linker for MOFs in the Type-I and Type-II synthesis, representing the first examples of CO2-derived MOFs. The electronegativity of coexisting metal ions determines the selective conversion of CO2 into formate and formylhydroborate. Formylhydroborate-based MOFs exhibit flexible pore sizes controlled by the pressure of CO2 during synthesis. In pursuit of highly porous structures, we present the Type-I synthesis of MOFs from CO2 via the in situ transformation of CO2 into carbamate linkers by amines. The direct conversion of diluted CO2 (400 ppm) in air into carbamate-based MOFs is also feasible. Coordination interactions stabilize the intrinsically labile carbamate in the MOF lattice. A recent study demonstrates that the Type-III synthesis using alkynylsilane precursors enables the synthesis of highly porous and stable carboxylate-based MOFs from CO2, which exhibit catalytic activity in CO2 conversion. We also extended the synthesis of MOFs from CO2 to COFs. The Type-III synthesis using a formamide monomer affords stable CO2-derived COFs showing proton conduction properties. The precise design of CO2-derived building units enables expansion of the structures and functionalities of CO2-derived MOF/COFs. Finally, we propose future challenges in this field: (i) expanding structural diversity through synthesis using external fields and (ii) exploring unique functionalities of CO2-derived MOF/COFs, such as carriers for CO2 capture and precursors for CO2 transformation. We anticipate that this Account will lay the foundation for exploring new chemistry of the conversion of CO2 into porous materials.

Relevance and Potential Applications of C2-Carboxylated 1,3-Azoles

Carbon dioxide (CO2) is an economically viable and abundant carbon source that can be incorporated into compounds such as C2-carboxylated 1,3-azoles relevant to the pharmaceutical, cosmetics, and pesticide industries. Of the 2.4 million commercially available C2-unsubstituted 1,3-azole compounds, less than 1 % are currently purchasable as their C2-carboxylated derivatives, highlighting the substantial gap in compound availability. This availability gap leaves ample opportunities for exploring the synthetic accessibility and use of carboxylated azoles in bioactive compounds. In this study, we analyze and quantify the relevance of C2-carboxylated 1,3-azoles in small-molecule research. An analysis of molecular databases such as ZINC, ChEMBL, COSMOS, and DrugBank identified relevant C2-carboxylated 1,3-azoles as anticoagulant and aroma-giving compounds. Moreover, a pharmacophore analysis highlights promising pharmaceutical potential associated with C2-carboxylated 1,3-azoles, revealing the ATP-sensitive inward rectifier potassium channel 1 (KATP) and Kinesin-like protein KIF18 A as targets that can potentially be addressed with C2-carboxylated 1,3-azoles. Moreover, we identified several bioisosteres of C2-carboxylated 1,3-azoles. In conclusion, further exploration of the chemical space of C2-carboxylated 1,3-azoles is recommended to harness their full potential in drug discovery and related fields.

Imidazolium and Pyridinium-Based Ionic Porous Organic Polymers: Advances in Transformative Solutions for Oxoanion Sequestration and Non-Redox CO2 Fixation

The rapid pace of industrialization has led to a multitude of detrimental environmental consequences, including water pollution and global warming. Consequently, there is an urgent need to devise appropriate materials to address these challenges. Ionic porous organic polymers (iPOPs) have emerged as promising materials for oxoanion sequestration and non-redox CO2 fixation. Notably, iPOPs offer hydrothermal stability, structural tunability, a charged framework, and readily available nucleophilic counteranions. This review explores the significance of pores and charged functionalities alongside design strategies outlined in existing literature, mainly focusing on the incorporation of pyridinium and imidazolium units into nitrogen-rich iPOPs for oxoanion sequestration and non-redox CO2 fixation. The present review also addresses the current challenges and future prospects, delineating the design and development of innovative iPOPs for water treatment and heterogeneous catalysis.

Not so inert mer-tris-chelate cobalt(III) complex of a hydroxy-pyridine functionalized NHC ligand for cyclic carbonate synthesis

The homoleptic hydroxy-pyridine functionalized Co(III)-NHC complex (2) demonstrates extraordinary catalytic activity towards the CO2 cycloaddition under mild conditions. Using this catalyst and TBAB, the highest TON (666 667) and TOF (52 713 h-1) were achieved compared to previously reported cobalt catalysts.

Cobalt-catalyzed reductive cross-coupling: a review

Transition-metal-catalyzed reductive cross-coupling is highly efficient for forming C-C bonds. It earns its limelight from its application by coupling unreactive electrophilic substrates to synthesize a variety of carbon-carbon bonds with various hybridizations (sp, sp2, and sp3), late-stage functionalization, and bioactive molecules' synthesis. Reductive cross-coupling is challenging to bring selectivity but promising approach. Cobalt is comparatively more affordable than other highly efficient metals e.g., palladium and nickel but cobalt catalysis is still facing efficacy challenges. Researchers are trying to harness the maximum out of cobalt's catalytic properties. Shortly, with efficiency achieved combined with the affordability of cobalt, it will revolutionize industrial applications. This review gives insight into the core of cobalt-catalyzed reductive cross-coupling reactions with a variety of substrates forming a range of differently hybridized coupled products.

Coupling CO2 Electroreduction to CO with alkyne Alkoxycarbonylation

The alkyne alkoxycarbonylation to α- or β-substituted acrylates was coupled with the electrocatalytic reduction of CO2 to CO. The CO-enriched gaseous mixture produced from the electrocatalytic reduction of CO2 was collected and directly used in the alkyne alkoxycarbonylation. The CO content was found to be critical to the process of carbonylation, and satisfying results were attained by using the gas mixture containing >15 vol % CO. This method offered an efficient but simple CO source from CO2 electroreduction to the alkoxycarbonylation reaction in two-compartment manner.

Visible-Light Photoredox-Catalyzed Direct Carboxylation of Tertiary C(sp3)-H Bonds with CO2: Facile Synthesis of All-Carbon Quaternary Carboxylic Acids

Direct carboxylation of C-H bonds with CO2 represents an attractive strategy to synthesize valuable carboxylic acids with high atom, step, and redox economy. Although great progress has been achieved in this field, catalytic carboxylation of tertiary C(sp3)-H bonds still remains challenging due to their inherent inertness and significant steric hindrance. Herein, we report a direct carboxylation of tertiary benzylic C(sp3)-H bonds with CO2 via visible-light photoredox catalysis. Various all-carbon quaternary carboxylic acids, which are of significant importance in medicinal chemistry, are successfully obtained with high yields. This direct carboxylation is characterized by good functional group tolerance, broad substrate scope, and mild operational conditions. Furthermore, our methodology enables the efficient and rapid synthesis of key drug or bioactive molecules, such as carbetapentane, caramiphen, and PRE-084 (σ1 receptor agonist), and facilitates various functionalizations of C(sp2)-H bonds using the directing ability of target carboxylic acids, thus highlighting its practical applications. Mechanistic studies indicate that a carbanion, which serves as the key intermediate to react with CO2, is catalytically generated via a single electron reduction of a benzylic radical through a consecutive photoinduced electron transfer process.

Unveiling Advancements: Trends and Hotspots of Metal-Organic Frameworks in Photocatalytic CO2 Reduction

Metal-organic frameworks (MOFs) are robust, crystalline, and porous materials featured by their superior CO2 adsorption capacity, tunable energy band structure, and enhanced photovoltaic conversion efficiency, making them highly promising for photocatalytic CO2 reduction reaction (PCO2RR). This study presents a comprehensive examination of the advancements in MOFs-based PCO2RR field spanning the period from 2011 to 2023. Employing bibliometric analysis, the paper scrutinizes the widely adopted terminology and citation patterns, elucidating trends in publication, leading research entities, and the thematic evolution within the field. The findings highlight a period of rapid expansion and increasing interdisciplinary integration, with extensive international and institutional collaboration. A notable emphasis on significant research clusters and key terminologies identified through co-occurrence network analysis, highlighting predominant research on MOFs such as UiO, MIL, ZIF, porphyrin-based MOFs, their composites, and the hybridization with photosensitizers and molecular catalysts. Furthermore, prospective design approaches for catalysts are explored, encompassing single-atom catalysts (SACs), interfacial interaction enhancement, novel MOF constructions, biocatalysis, etc. It also delves into potential avenues for scaling these materials from the laboratory to industrial applications, underlining the primary technical challenges that need to be overcome to facilitate the broader application and development of MOFs-based PCO2RR technologies.

MIL-101(Cr)/aminoclay nanocomposites for conversion of CO2 into cyclic carbonates

We present the use of an amine functionalized two-dimensional clay i.e., aminoclay (AC), in the chemistry of a three-dimensional metal-organic framework (MOF) i.e., MIL-101(Cr), to prepare MIL-101(Cr)/AC composites, which are exploited as catalysts for efficient conversion of CO2 gas into cyclic carbonates under ambient reaction conditions. Three different MOF nanocomposites, denoted as MIL-101(Cr)/AC-1, MIL-101(Cr)/AC-2, and MIL-101(Cr)/AC-3, were synthesized by an in situ process by adding different amounts of AC to the precursor solutions of the MIL-101(Cr). The composites were characterized by various techniques such as FT-IR, PXRD, FESEM, EDX, TGA, N2 adsorption, as well as CO2 and NH3-TPD measurements. The composites were exploited as heterogeneous catalysts for CO2 cycloaddition reactions with different epoxides and the catalytic activity was investigated at atmospheric pressure under solvent-free conditions. Among all the materials, MIL-101(Cr)/AC-2 shows the best catalytic efficiency under the optimized conditions and exhibits enhanced efficacy compared to various MIL-101(Cr)-based MOF catalysts, which typically need either high temperature and pressure or a longer reaction time or a combination of all the parameters. The present protocol using MIL-101(Cr)/AC-2 as the heterogeneous catalyst gives 99.9% conversion for all the substrates into the products at atmospheric pressure.

Recent Advances in Electrochemical Carboxylation with CO2

ConspectusCarbon dioxide (CO2) is recognized as a greenhouse gas and a common waste product. Simultaneously, it serves as an advantageous and commercially available C1 building block to generate valuable chemicals. Particularly, carboxylation with CO2 is considered a significant method for the direct and sustainable production of important carboxylic acids. However, the utilization of CO2 is challenging owing to its thermodynamic stability and kinetic inertness. Recently, organic electrosynthesis has emerged as a promising approach that utilizes electrons or holes as environmentally friendly redox reagents to produce reactive intermediates in a controlled and selective manner. This technique holds great potential for the CO2 utilization.Since 2015, our group has been dedicated to exploring the utilization of CO2 in organic synthesis with a particular focus on electrochemical carboxylation. Despite the significant advancements made in this area, there are still many challenges, including the activation of inert substrates, regulation of selectivity, diversity in electrolysis modes, and activation strategies. Over the past 7 years, our team, with many great experts, has presented findings on electrochemical carboxylation with CO2 under mild conditions. In this context, we primarily highlight our contributions to selective electrocarboxylations, encompassing new reaction systems, selectivity control methods, and activation approaches.We commenced our research by establishing a Ni-catalyzed electrochemical carboxylation of unactivated aryl halides and alkyl bromides in conjunction with a useful paired anodic reaction. This approach eliminates the need for sacrificial anodes, rendering the carboxylation process sustainable. To further utilize the widely existing yet cost-effective alkyl chlorides, we have developed a deep electroreductive system to achieve carboxylation of unactivated alkyl chlorides and poly(vinyl chloride), allowing the direct modification and upgrading of waste polymers.Through precise adjustment of the electroreductive conditions, we successfully demonstrated the dicarboxylation of both strained carbocycles and acyclic polyarylethanes with CO2 via C-C bond cleavage. Furthermore, we have realized the dicarboxylative cyclization of unactivated skipped dienes to produce the valuable ring-tethered adipic acids through single-electron reduction of CO2 to the CO2 radical anion (CO2•-). In terms of the asymmetric carboxylation, Guo's and our groups have recently achieved the nickel-catalyzed enantioselective electroreductive carboxylation reaction using racemic propargylic carbonates and CO2, paving the way for the synthesis of enantioenriched propargylic carboxylic acids.In addition to the aforementioned advancements, Lin's and our groups have also developed new electrolysis modes to achieve regiodivergent C-H carboxylation of N-heteroarenes dictated by electrochemical reactors. The choice of reactors plays a crucial role in determining whether the hydrogen atom transfer (HAT) reagents are formed anodically, consequently influencing the carboxylation pathways of N-heteroarene radical anions in the distinct electrolyzed environments.

An isolable stannaimine and its cycloaddition/metathesis reactions with carbon dioxide

An N-heterocyclic stannylene :Sn(NONAd) (NONAd = [O(SiMe2NAd)2]2-, Ad = 1-adamantyl), reacts rapidly with 2,4,6-tricyclohexylphenyl azide (TCHP)N3, affording a stannaimine, (NONAd)SnN(TCHP). Solutions of (NONAd)SnN(TCHP) react immediately with carbon dioxide (CO2) to give a [2+2]-cycloaddition product, which, upon heating, subsequently engages in a metathesis process to give [Sn(NONAd)(μ-O)]2 and the bulky isocyanate, (TCHP)NCO.

Hydrogenation of CO2 to formate catalyzed by a Ru catalyst supported on a copolymerized porous organic polymer

The catalytic hydrogenation of carbon dioxide to formate is of great interest due to its significant role in CO2 utilization. In this study, a novel heterogeneous Ru(III) catalyst was prepared by immobilizing RuCl3 on a porous organic polymer (POP) obtained from 1,4-phthalaldehyde (PTA) and 4,4'-biphenyldicarboxaldehyde (BPDA) with melamine. A copolymerization strategy utilizing monomers of varying lengths was employed to prepare the POP-supported Ru catalyst with adjustable porosity. The optimization of the framework porosity resulted in enhanced CO2 affinity, accelerated mass transfer, and a remarkable enhancement in catalytic activity. A high turnover number (TON) of 2458 was achieved for the CO2 hydrogenation to formate in 2 h with catalyst Cat-3 under 3 MPa (CO2/H2 = 1 : 1) at 120 °C in 1 M Et3N aqueous solution. Moreover, the Cat-3 demonstrated good recyclability and was able to be reused for five consecutive runs, resulting in a high total TON of 9971.

Computational Study of the Ir-Catalyzed Formation of Allyl Carbamates from CO2

We have employed computational methods to investigate the iridium-catalyzed allylic substitution leading to the formation of enantioenriched allyl carbamates from carbon dioxide (CO2). The reaction occurs in several steps, with initial formation of an iridium-allyl, followed by nucleophilic attack by the carbamate formed in situ from CO2 and an amine. A detailed isomeric analysis shows that the rate-determining step differs for the (R)- and (S)-pathways. These insights are essential for understanding reactions involving enantioselective formation of allyl carbamates from CO2.

Electrochemical Synthesis of Itaconic Acid Derivatives via Chemodivergent Single and Double Carboxylation of Allenes with CO2

Leveraging electrochemistry, a new synthesis of non-natural derivatives of itaconic acid is proposed by utilizing carbon dioxide (CO2) as a valuable C1 synthon. An electrochemical cross-electrophile coupling between allenoates and CO2 was targeted, allowing for the synthesis of both mono- and di-carboxylation products in a catalyst- and additive-free environment (yields up to 87 %, 30 examples). Elaboration of the model mono-carboxylation product, and detailed cyclovoltammetric, as well as mechanistic analyses complete the present investigation.

Atomically Dispersed Metal Catalysts for the Conversion of CO2 into High-Value C2+ Chemicals

The conversion of carbon dioxide (CO2) into value-added chemicals with two or more carbons (C2+) is a promising strategy that cannot only mitigate anthropogenic CO2 emissions but also reduce the excessive dependence on fossil feedstocks. In recent years, atomically dispersed metal catalysts (ADCs), including single-atom catalysts (SACs), dual-atom catalysts (DACs), and single-cluster catalysts (SCCs), emerged as attractive candidates for CO2 fixation reactions due to their unique properties, such as the maximum utilization of active sites, tunable electronic structure, the efficient elucidation of catalytic mechanism, etc. This review provides an overview of significant progress in the synthesis and characterization of ADCs utilized in photocatalytic, electrocatalytic, and thermocatalytic conversion of CO2 toward high-value C2+ compounds. To provide insights for designing efficient ADCs toward the C2+ chemical synthesis originating from CO2, the key factors that influence the catalytic activity and selectivity are highlighted. Finally, the relevant challenges and opportunities are discussed to inspire new ideas for the generation of CO2-based C2+ products over ADCs.

Direct Access to Benzolactams and Benzolactones via Nickel Catalyzed Carbonylation with CO2

A new nickel catalyzed cross-electrophile coupling for accessing γ-lactams (isoindolinones) as well as γ-lactones (isobenzofuranones) via carbonylation with CO2 is documented. The protocol exploits the synergistic role of redox-active Ni(II) complexes and AlCl3 as a CO2 activator/oxygen scavenger, leading to the formation of a wide range of cyclic amides and esters (28 examples) in good to high yields (up to 87 %). A dedicated computational investigation revealed the multiple roles played by AlCl3. In particular, the simultaneous transient protection of the pendant amino group of the starting reagents and the formation of the electrophilically activated CO2-AlCl3 adduct are shown to concur in paving the way for an energetically favorable mechanistic pathway.

Ionic Liquid-Catalyzed CO2 Conversion for Valuable Chemicals

CO2 is not only the main gas that causes the greenhouse effect but also a resource with abundant reserves, low price, and low toxicity. It is expected to become an important "carbon source" to replace oil and natural gas in the future. The efficient and clean resource utilization of CO2 has shown important scientific and economic value. Making full use of abundant CO2 resources is in line with the development direction of green chemistry and has attracted the attention of scientists. Environmentally friendly ionic liquids show unique advantages in the capture and conversion of CO2 due to their non-volatilization, designable structure, and good solubility, and show broad application prospects. The purpose of this paper is to discuss the research on the use of an ionic liquid as a catalyst to promote the synthesis of various value-added chemicals in CO2, hoping to make full use of CO2 resources while avoiding the defects of the traditional synthesis route, such as the use of highly toxic raw materials, complicated operation, or harsh reaction conditions. The purpose of this paper is to provide reference for the application and development of ionic liquids in CO2 capture and conversion.

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.

Organomagnesia: Reversibly High Carbon Dioxide Uptake by Magnesium Pyrazolates

A series of new pyrazolate and mixed pyrazolate/pyrazole magnesium complexes is described and their reactivity toward carbon dioxide is examined. The dimeric complex [Mg(pzt Bu, t Bu)2]2 inserts CO2 instantly and quantitatively forming the tetrameric complex [Mg(CO2·pzt Bu, t Bu)2]4 and monomeric donor-stabilized [Mg(CO2·pzt Bu, t Bu)2(thf)2]. Complexes of the type [Mgx(pzR,R)2 x(HpzR,R)y]n (R = iPr, tBu) engage in similar insertion reactions involving dissociation of the carbamic acid HOOCpzR,R. Even solid polymeric derivatives [Mg(pzR,R)2]n (R = Me, H) react instantaneously and exhaustively with CO2, the resulting [Mg(CO2·pz)2]m featuring a CO2 capacity of 35.7 wt% (8.2 mmol g-1). All described magnesium pyrazolates display completely reversible CO2 uptake in solution and in the solid state, respectively, as monitored via VT 1H NMR and in situ FTIR spectroscopy as well as thermogravimetric analysis. Fluorinated [Mg2(pzCF3,CF3)4(thf)3] does not yield any isolable CO2 insertion product but exhibits the highest activity in the catalytic transformation of epoxides and CO2 to cyclic carbonates.

Immobilization of Silver(I) Ions on Amino-Functionalized Chromium(III) Terephthalate with Organophosphine and its C-H Carboxylation of a Heteroaromatic Compound

A newly designed heterogenized catalyst that incorporates silver(I) ions with 2-(dicyclohexylphosphaneyl)acetaldehyde (PCy2 aldehyde) into amino-functionalized chromium(III) terephthalate is developed. Silver(I) ions were robustly immobilized on the amino-functionalized chromium(III) terephthalate, which contains an imine bond formed by the reaction with PCy2 aldehyde. The Ag(I) ion is coordinated with the phosphine in the imine group to create MIL-101-AP(Ag). Characterizations were carefully carried out according to the synthetic steps. The catalytic performance of MIL-101-AP(Ag) was evaluated through the C-H carboxylation of thiophene-2-carbonitrile, achieving a 10 % yield with a turnover number of 1.0. The recyclability of the MIL-101-AP(Ag) catalyst was successfully demonstrated with five cycle, with no loss in activity and selectivity observed. This approach, which involves the formation of an imine bond to facilitate silver loading with phosphine on amino-functionalized MIL-101(Cr), exhibits significant potential for both CO2 fixation and C-H carboxylation, thereby highlighting the modified material's promise as a sustainable catalyst.

The Structure of Carbon Dioxide at the Air-Water Interface and its Chemical Implications

The efficient reduction of CO2 into valuable products is a challenging task in an international context marked by the climate change crisis and the need to move away from fossil fuels. Recently, the use of water microdroplets has emerged as an interesting reaction media where many redox processes which do not occur in conventional solutions take place spontaneously. Indeed, several experimental studies in microdroplets have already been devoted to study the reduction of CO2 with promising results. The increased reactivity in microdroplets is thought to be linked to unique electrostatic solvation effects at the air-water interface. In the present work, we report a theoretical investigation on this issue for CO2 using first-principles molecular dynamics simulations. We show that CO2 is stabilized at the interface, where it can accumulate, and that compared to bulk water solution, its electron capture ability is larger. Our results suggest that reduction of CO2 might be easier in interface-rich systems such as water microdroplets, which is in line with early experimental data and indicate directions for future laboratory studies. The effect of other relevant factors which could play a role in CO2 reduction potential is discussed.

Chemical fixation of CO2/CS2 to access iodoallenyl oxazolidinones and allenyl thiazolidine-thiones

Constructing heterocyclic compounds by chemical fixation of CO2/CS2 as a C1 building block is a promising approach. An efficient and environmentally friendly synthetic approach has been developed using CO2/CS2 to prepare complicated allenyl heterocycles with high yields and diastereoselectivities in a metal-free manner under mild conditions. NIS promoted CO2 fixation and the cyclization reaction by exclusive 1,4-syn-addition of 1,3-enynes rather than 1,2-addition or 3,4-addition, while CS2 participated in unique 1,4-syn-hydrothiolation of 1,3-enynes to afford allenyl heterocycles with different reaction patterns.

Interfacial charge-transfer transitions enable photovoltaic conversion with CO2-fixation products

We demonstrate that organic-inorganic interfacial charge-transfer transitions enable favourable photovoltaic conversion with CO2-fixation products such as aromatic carboxylic acids, verifying a new possibility of CO2-fixation products in the development of optoelectronic conversion materials.

A robust Fe-based heterogeneous photocatalyst for the visible-light-mediated selective reduction of an impure CO2 stream

The transformation of CO2 into value-added products from an impure CO2 stream, such as flue gas or exhaust gas, directly contributes to the principle of carbon capture and utilization (CCU). Thus, we have developed a robust iron-based heterogeneous photocatalyst that can convert the exhaust gas from the car into CO with an exceptional production rate of 145 μmol g-1 h-1. We characterized this photocatalyst by PXRD, XPS, ssNMR, EXAFS, XANES, HR-TEM, and further provided mechanistic experiments, and multi-scale/level computational studies. We have reached a clear understanding of its properties and performance that indicates that this highly robust photocatalyst could be used to design an efficient visible-light-mediated reduction strategy for the transformation of impure CO2 streams into value-added products.

Electroreductive carboxylation of benzylphosphonium salts with CO2 through the cleavage of the C(sp3)-P bond

Herein, a electroreductive carboxylation of benzylphosphonium salts was achieved by the cleavage of the C(sp3)-P bond, and various valuable arylacetic acids could be synthesized by this strategy. Also, based on control experiments and previous studies, a plausible reaction mechanism was proposed to explain the reaction process. The establishment of this procedure will provide a new paradigm for the functionalization of alkyl phosphonium salts.

Catalytic Regio- and Enantioselective Remote Hydrocarboxylation of Unactivated Alkenes with CO2

The catalytic regio- and enantioselective hydrocarboxylation of alkenes with carbon dioxide is a straightforward strategy to construct enantioenriched α-chiral carboxylic acids but remains a big challenge. Herein we report the first example of catalytic highly enantio- and site-selective remote hydrocarboxylation of a wide range of readily available unactivated alkenes with abundant and renewable CO2 under mild conditions enabled by the SaBOX/Ni catalyst. The key to this success is utilizing the chiral SaBOX ligand, which combines with nickel to simultaneously control both chain-walking and the enantioselectivity of carboxylation. This process directly furnishes a range of different alkyl-chain-substituted or benzo-fused α-chiral carboxylic acids bearing various functional groups in high yields and regio- and enantioselectivities. Furthermore, the synthetic utility of this methodology was demonstrated by the concise synthesis of the antiplatelet aggregation drug (R)-indobufen from commercial starting materials.