Carboxylative cyclization of propargylic alcohols with carbon dioxide: A facile and Green route to α-methylene cyclic carbonates

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.

In Situ Anchoring of Small-Sized Silver Nanoparticles on Porphyrinic Triazine-Based Frameworks for the Conversion of CO2 into α-Alkylidene Cyclic Carbonates with Outstanding Catalytic Activities under Ambient Conditions

The preparation of catalytic hybrid materials by introducing highly dispersed metallic nanoparticles into porous organic polymers (POPs) may be an ideal and promising strategy for integrated CO2 capture and conversion. In terms of the carboxylative cyclization of propargyl alcohols with CO2, the anchoring of silver nanoparticles (AgNPs) on functional POPs to fabricate efficient heterogeneous catalysts is considered to be quite intriguing but remains challenging. In the contribution, well-dispersed AgNPs were successfully anchored onto the porphyrinic triazine-based frameworks by a simple "liquid impregnation and in situ reduction" strategy. The presence of N-rich dual active sites, porphyrin and triazine, which acted as the electron donor and acceptor, respectively, offered a huge opportunity for the nucleation and growth of metal nanoparticles. Significantly, the as-prepared catalyst Ag/TPP-CTF shows excellent catalytic activity (up to 99%) toward the carboxylative cyclization of propargyl alcohols with CO2 at room temperature, achieving record-breaking activities (TOF up to 615 h-1 at 1 bar and 3077 h-1 at 10 bar). Moreover, the catalyst can be easily recovered and reused at least 10 times with retention of high catalytic activity. The possible mechanism involves small-sized AgNP-mediated alkyne activation, which may promote highly efficient and green conversion of CO2. This work paves the way for immobilizing metal nanoparticles onto functional POPs by surface structure changes for enhanced CO2 catalysis.

Recent progress in reductive carboxylation of C-O bonds with CO2

Transformation of carbon dioxide (CO2) into value-added organic compounds has attracted increasing interest of scientific community in the last few decades, not only because CO2 is the primary greenhouse gas that drives global climate change and ocean acidification, but also because it has been regarded as a plentiful, nontoxic, nonflammable and renewable one-carbon (C1) feedstock. Among the various CO2-conversion processes, carboxylation reactions represent one of the most beautiful and attractive research topics in the field, since it offers the possibility for the construction of synthetically and biologically important carboxylic acids from various easily accessible (pseudo)halides, organosilicon, and organoboron compounds. The purpose of this review is to summarize the available literature on deoxygenative carboxylation of alcohols and their derivatives utilizing CO2 as a carboxylative reagent. Depending on the C-O compounds employed, the paper is divided into five major sections. The direct dehydroxylative carboxylation of free alcohols is discussed first. This is followed by reductive carboxylation of carboxylates, triflates, and tosylates. In the final section, the only reported example on catalytic carboxylation of fluorosulfates will be covered. Notably, special attention has been paid on the mechanistic aspects of the reactions that may provide new insights into catalyst improvement and development, which currently mainly relies on the use of transition metal catalysts.

Understanding of the interactions between azole-anion-based ionic liquids and 2-methyl-3-butyn-2-ol from the experimental perspective: the cage effect

The interactions between azole-anion-based ionic liquids (AILs) and 2-methyl-3-butyn-2-ol (MBY) play an important role in AIL-promoted carboxylative cyclization of MBY with CO₂. To better understand the interactions between AILs ([P₆₆₆₁₄][Im], [P₆₆₆₁₄][4-MeIm], and [P₆₆₆₁₄][4-BrIm]) and MBY, a detailed investigation from the experimental perspective has been carried out in this study. The results show that the derivative of viscosity (η) with the mole fraction of AIL (x_AIL) of AIL + MBY mixtures appears to have the maximum value when x_AIL ≈ 0.3, while ¹H NMR chemical shifts of P-CH₂ of [P₆₆₆₁₄]⁺ reach the minimum value at x_AIL ≈ 0.3, indicating that [P₆₆₆₁₄]⁺ of AILs tend to self-aggregate. The interaction parameters (g_ji-g_ii) of the systems obtained from η by the Eyring-UNIQUAC equation are positive, and the difference between the bulk and local composition (x_i-x_ii) is always negative, indicating that AILs can interact with MBY. Moreover, excess molar volumes and isentropic compressibility deviations are all negative deviations and become more negative as the temperature increases, reaching a minimum value at x_AIL ≈ 0.30, indicating that azole-based anions can form H-bonds with MBY, and MBY molecules tend to enter the aggregates formed by AILs. Consequently, the cage effect is proposed to describe the interactions between AILs and MBY: MBY first enters the cage formed by the aggregation of [P₆₆₆₁₄]⁺, and then forms H-bonds with azole-based anions. Finally, the sizes of the particles of the [P₆₆₆₁₄][Im] + MBY mixture from dynamic light scattering increase first and then decrease with x_AIL, with the maximum of 122 nm at x_AIL ≈ 0.25, which confirms the rationality of the cage effect.

Methods for Direct Reductive N-Methylation of Nitro Compounds

Direct reductive N-methylation of inexpensive and readily available nitro compounds as raw material feedstocks is more attractive and straightforward compared with conventional N-methylation of amines to prepare biologically and pharmaceutically important N-methylated amine derivatives. This strategy for synthesis of N-methylamines avoids prepreparation of NH-free amines and therefore significantly shortens the separation and purification steps. In recent years, numerous methylating agents and catalytic systems have been reported for this appealing transformation. Thus, it is an appropriate time to summarize such advances. This review elaborates on the most important discoveries and advances in this research arena, with special emphasis on the mechanistic aspect of reactions that may provide new insights into catalyst improvement.

Exovinylene Cyclic Carbonates: Multifaceted CO2 -Based Building Blocks for Modern Chemistry and Polymer Science

Carbon dioxide is a renewable, inexhaustible, and cheap alternative to fossil resources for the production of fine chemicals and plastics. It can notably be converted into exovinylene cyclic carbonates, unique synthons gaining momentum for the preparation of an impressive range of important organic molecules and functional polymers, in reactions proceeding with 100 % atom economy under mild operating conditions in most cases. This Review summarizes the recent advances in their synthesis with particular attention on describing the catalysts needed for their preparation and discussing the unique reactivity of these CO₂ -based heterocycles for the construction of diverse organic building blocks and (functional) polymers. We also discuss the challenges and the future perspectives in the field.

Recent Advances in the Synthesis of Five-Membered Cyclic Carbonates and Carbamates from Allylic or Propargylic Substrates and CO2

The organic carbamates and carbonates are highly desirable compounds that have found a wide range of applications in drug design, medicinal chemistry, material science, and the polymer industry. The development of new catalytic carbonate and carbamate forming reactions, which employ carbon dioxide as a cheap, green, abundant, and easily available reagent, would thus represent an ideal substitution for existing methods. In this review, the advancements in the catalytic conversion of allylic and propargylic alcohols and amines to corresponding five-membered cyclic carbonates and carbamates are summarized. Both the metal- and the organocatalyzed methods are reviewed, as well as the proposed mechanisms and key intermediates of the illustrated carbonate and carbamate forming reactions.

Tandem Reactions Based on the Cyclization of Carbon Dioxide and Propargylic Alcohols: Derivative Applications of α-Alkylidene Carbonates

As a well-known greenhouse gas, carbon dioxide (CO2) has attracted increasing levels of attention in areas of energy, environment, climate, etc. Notably, CO2 is an abundant, nonflammable, and renewable C1 feedstock in view of chemistry. Therefore, the transformation of CO2 into organic compounds is an extremely attractive research topic in modern green and sustainable chemistry. Among the numerous CO2 utilization methods, carboxylative cycloaddition of CO2 into propargylic alcohols is an ideal route due to the corresponding products, α-alkylidene cyclic carbonates, which are a series of highly functionalized compounds that supply numerous potential methods for the construction of various synthetically and biologically valuable agents. This cyclization reaction has been intensively studied and systematically summarized, in the past years. Therefore, attention has been gradually transferred to produce more derivative compounds. Herein, the tandem reactions of this cyclization with hydration, amination, alcoholysis, and isomerization to synthesize α-hydroxyl ketones, oxazolidinones, carbamates, unsymmetrical carbonates, tetronic acids, ethylene carbonates, etc. were systematically reviewed.

Advances in Palladium-Catalyzed Carboxylation Reactions

In this short review, we highlight the advancements in the field of palladium-catalyzed carbon dioxide utilization for the synthesis of high value added organic molecules. The review is structured on the basis of the kind of substrate undergoing the Pd-catalyzed carboxylation process. Accordingly, after the introductory section, the main sections of the review will illustrate Pd-catalyzed carboxylation of olefinic substrates, acetylenic substrates, and other substrates (aryl halides and triflates).

A heterogeneous bifunctional silica-supported Ag2O/Im+Cl− catalyst for efficient CO2 conversion

Reusable heterogeneous bifunctional silica-supported Ag2O/Im+Cl− catalyst in carboxylative cyclization reaction of propargyl alcohols by the efficient utilization of CO2 under ambient conditions.

Study on Selected Metal-Organic Framework-Based Catalysts for Cycloaddition Reaction of CO2 with Epoxides: A Highly Economic Solution for Carbon Capture and Utilization

The level of carbon dioxide in the atmosphere is growing rapidly due to fossil fuel combustion processes, heavy oil, coal, oil shelter, and exhausts from automobiles for energy generation, which lead to depletion of the ozone layer and consequently result in global warming. The realization of a carbon-neutral environment is the main focus of science and academic researchers of today. Several processes were employed to minimize carbon dioxide in the air, some of which include the utilization of non-fossil sources of energy like solar, nuclear, and biomass-based fuels. Consequently, these sources were reported to have a relatively high cost of production and maintenance. The applications of both homogeneous and heterogeneous processes in carbon capture and storage were investigated in recent years and the focus now is on the conversion of CO2 into useful chemicals and compounds. It was established that CO2 can undergo cycloaddition reaction with epoxides under the influence of special catalysts to give cyclic carbonates, which can be used as value-added chemicals at a different level of pharmaceutical and industrial applications. Among the various catalysts studied for this reaction, metal-organic frameworks are now on the frontline as a potential catalyst due to their special features and easy synthesis. Several metal-organic framework (MOF)-based catalysts were studied for their application in transforming CO2 to organic carbonates using epoxides. Here, we report some recent studies of porous MOF materials and an in-depth discussion of two repeatedly used metal-organic frameworks as a catalyst in the conversion of CO2 to organic carbonates.

Ionic-Liquid-Catalyzed Approaches under Metal-Free Conditions

ConspectusMetal-free catalysis is a promising protocol to access chemicals without metal contamination. Ionic liquids (ILs) that are entirely composed of organic cations and inorganic/organic anions have emerged as promising alternatives to molecular solvents and metal catalysts due to their unique properties such as structural tunability, the coexistence of multiple interactions among ions (e.g., electrostatic interaction, hydrogen bonding, van de Waals forces, acid/base interactions, hydrophilic/hydrophobic interactions, etc.), unique affinity for a wide range of chemicals, good chemical and thermal stability, and quite low volatility. ILs have shown potential applications in various chemical processes.In this Account, we systematically described our most recent work on IL-catalyzed approaches under metal-free conditions. The first section presents the IL-catalyzed strategies toward the transformation of CO2 to value-added chemicals, focusing on the CO2-reactive IL-catalyzed CO2 transformation to various heterocycles and the IL-catalyzed reductive transformation of CO2 to chemicals. In these approaches, we designed task-specific ILs that are able to chemically capture and activate CO2 via forming anion-based carbonate/carbamate or cation-based carboxylate/carbamate intermediates, thus further accomplishing its transformation to a series of heterocycles including quinazoline-2,4(1H,3H)-diones, cyclic carbonates, 2-oxazolidinones, oxazolones, and benzimidazolones under metal-free conditions. For the IL-catalyzed approaches to reducing CO2 with hydrosilanes to chemicals, we employed ILs capable of activating the Si-H bond in hydrosilanes and the N-H bond in amine substrates via H-bonding, thus achieving the reductive transformation of CO2 to formamides, benzimidazoles, and benzothiazoles via cooperative catalysis. The second section describes our finding on the IL-catalyzed hydration of the C≡C bond in propargylic alcohols. Azolate anion-based ILs that can chemically capture CO2 via the formation of carbamates could serve as robust nucleophiles to attack the C≡C bond in propargylic alcohols and then efficiently catalyze the hydration of propargylic alcohols to produce α-hydroxy ketones with the assistance of atmospheric CO2 gas under metal-free conditions. The third section unveils the cooperative catalysis strategy of hydrogen bond donors and acceptors of ILs for chemical reactions. In the hydrogen-bonding catalysis protocols, cations of the ILs act as H-bond donors and anions, as acceptors, forming H-bonds with the reactant molecules, respectively, in opposite ways, which can cooperatively catalyze the ring-closing C-O/C-O bond metathesis reactions of aliphatic diethers to O-heterocycles, the dehydrative etherification of alcohols to ethers, and direct oxidative esterification of alcohols to esters. We believe that these IL-catalyzed metal-free processes and strategies display promising practical applications, and their commercialization would bring great benefits to the production of the as-afforded value-added chemicals.

Expanded Ring NHC Silver Carboxylate Complexes as Efficient and Reusable Catalysts for the Carboxylative Cyclization of Unsubstituted Propargylic Derivatives

Stabilized by a bulky N-heterocyclic carbene [^BP DPr, 1,3-bis(2,6-diisopropylphenyl)-1,3-diazonine-2-ylidene] ligand, new silver carboxylate complexes of the form ^BP DPrAgO₂ C-R (R=Me, Ph) have been synthesized and fully characterized in solution and in the solid state and implemented as sole catalysts (base-, additive-, and, in some cases, solvent-free) in the challenging fixation of carbon dioxide to unsubstituted propargylic derivatives for the synthesis of oxazolidinones and α-methylene cyclic carbonates. Derived from X-ray diffraction studies, the molecular geometry and the concept of buried volume were employed to describe the structural and steric features of these silver complexes. Their stability and efficiency as catalysts have been demonstrated by the synthesis of 29 carboxylation products (72-98 % yield) at low catalyst loadings (0.01-1.5 mol%). Characteristics are high turnover numbers (up to 9400), catalyst recyclability (up to 96 % yield after the 7th cycle with no decomposition of the silver complex), and the possibility to scale-up the reaction.

Vicinal halo-trifluoromethylation of alkenes

Both trifluoromethyl and halide groups are widely found in medicinally and pharmaceutically important compounds and, moreover, organohalides are commonly used as versatile intermediates in synthetic organic chemistry. Due to their prevalence and easy accessibility, alkene halo-trifluoromethylation provides a convenient way to install these valuable functionalities in complex targets. In this review, we summarize recent advances and achievements in this fast-growing research field. For clarity, the reactions were classified according to the type of halogen atom.

Green Synthesis of 2-Oxazolidinones by an Efficient and Recyclable CuBr/Ionic Liquid System via CO2, Propargylic Alcohols, and 2-Aminoethanols

With the aim of profitable conversion of carbon dioxide (CO2) in an efficient, economical, and sustainable manner, we developed a CuBr/ionic liquid (1-butyl-3-methylimidazolium acetate) catalytic system that could efficiently catalyze the three-component reactions of propargylic alcohols, 2-aminoethanols, and CO2 to produce 2-oxazolidinones and α-hydroxy ketones. Remarkably, this catalytic system employed lower metal loading (0.0125–0.5 mol%) but exhibited the highest turnover number (2960) ever reported, demonstrating its excellent activity and sustainability. Moreover, our catalytic system could efficiently work under 1 atm of CO2 pressure and recycle among the metal-catalyzed systems.

Synthesis of α-alkylidene cyclic carbonates via CO2 fixation under ambient conditions promoted by an easily available silver carbamate

A series of α-alkylidene cyclic carbonates has been synthesized under mild conditions using silver carbamate Ag(O₂CNEt₂) in combination with PPh₃.

A new 3D luminescent Ba-organic framework with high open metal sites: CO2 fixation, luminescence sensing, and dye sorption

A new synthesized 3D luminescent Ba-organic framework (1) may be used as a recyclable heterogeneous catalyst for fixation of CO₂ and has excellent response and sensitivity for pollutant ions. Moreover, 1 exhibits the particular selective sorption towards Congo red (CR) dye.

Recent trends in the direct oxyphosphorylation of C-C multiple bonds

Due to the wide importance of β-phosphorylated ketones as key building-blocks in the fabrication of various pharmaceutically active organophosphorus compounds, finding new and truly efficient methods for their preparation from simple, low-cost and ubiquitous feedstock materials within a single click is an interesting subject in organic synthesis. Recently, oxyfunctionalization of carbon-carbon multiple bonds has arisen as a straightforward and versatile tool for the synthesis of complex organic molecules from the simple and easily accessible alkenes/alkynes via a single operation. In this context, oxyphosphorylation of alkenes/alkynes with P(O)-H compounds has attracted considerable attention as a unique procedure for the construction of β-phosphorylated ketones. In this review, we outline the recent advances and developments in this fast-growing research field with particular emphasis on the mechanistic aspects of reaction.

A dual-functional urea-linked conjugated porous polymer anchoring silver nanoparticles for highly efficient CO2 conversion under mild conditions

A dual-functional urea-linked conjugated porous polymer (UCPP) assembled by enol-imine with ordered unit arrays that act as potential anchoring sites in the networks was fabricated, and was further applied as a support for Ag nanoparticles by the coordinate interaction between them. The UCPP not only can well confine the Ag particle size and facilitate high dispersion, but also can afford special CO₂-philic moieties to enhance the adsorption properties. The resulting Ag@UCPP as a heterogeneous catalyst exhibited excellent activity for the carboxylative cyclization of propargyl alcohols with CO₂ under mild conditions, together with good recyclability, which is probably attributed to the synergistic effect of the UCPP on the adsorption and activation of CO₂ and the immobilization of Ag nanoparticles. This work affords possible opportunities for the design and synthesis of a heterogeneous catalyst toward CO₂ conversion.

Solvent-Dependent Assembly and Magnetic Relaxation Behaviors of [Cu4I3] Cluster-Based Lanthanide MOFs: Acting as Efficient Catalysts for Carbon Dioxide Conversion with Propargylic Alcohols

Two structurally similar metal-organic frameworks (MOFs) [Dy₂Cu₄I₃(IN)₇(DMF)₂]·DMF (1) and [Dy₂Cu₄I₃(IN)₇(DMA)₂]·DMA (2) (HIN = isonicotinic acid) feathering different coordinated solvent molecules were successfully isolated by tuning the types of solvents in the reaction system. Structural tests indicate that 1 and 2 are both built from 1D Dy(III) chains and copper iodide clusters [Cu₄I₃], generating into three-dimensional frameworks with an open 1D channel along the a axis. 1 and 2 display extensive and excellent solvent stability. Magnetic studies of 1 and 2 indicate that they exhibit interesting solvent-dependent magnetization dynamics. Importantly, 1 and 2 can act as highly effective catalysts for the carboxylic cyclization of propargyl alcohols with carbon dioxide (CO₂) under ambient operating conditions. Additionally, the substrate scope was further explored over compound 1 based on the optimal conditions, and it exhibits efficient cyclic carboxylation of various terminal propargylic alcohols with CO₂. This research offers an effective approach for the solvent-guided synthesis of MOFs materials and also presents the great application value of MOFs in CO₂ chemical conversion.