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.

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.

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.

Room-Temperature Synthesis of a Hollow Microporous Organic Polymer Bearing Activated Alkyne IR Probes for Nonradical Thiol-yne Click-Based Post-Functionalization

This work shows that hollow microporous organic polymer (H-MOP-A) with activated internal alkynes as IR probes can be prepared by template synthesis based on acyl Sonogashira-Hagihara coupling at room temperature. The H-MOP-A is a versatile platform in the main chain PSM based on nonradical thiol-yne click reaction. Moreover, an IR peak of internal alkynes in the H-MOP-A is very intense and could be utilized in the monitoring of thiol-yne click-based main chain PSM. The functionalized H-MOP-A with carboxylic acids (H-MOP-CA) showed efficient adsorption toward Ag⁺ ions. The resultant H-MOP-CA-Ag showed excellent performance in the CO₂ fixation to α-alkylidene cyclic compounds.

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.

Tubular metal organic frameworks from the curvature of 2D-honeycombed metal coordination

A tubular MOF with adequate active sites is prepared by the bending of metal-coordinated honeycombed frameworks via titration and shows fast catalytic kinetics with lower catalytic loading for CO2 conversion. The TON is observed to be 2300 and the corresponding TOF of up to 173 h-1 is achieved for the first time.

Formation of CX Bonds in CO2 Chemical Fixation Catalyzed by Metal-Organic Frameworks

Transformation of CO₂ based on metal-organic framework (MOF) catalysts is becoming a hot research topic, not only because it will help to reduce greenhouse gas emission, but also because it will allow for the production of valuable chemicals. In addition, a large number of impressive products have been synthesized by utilizing CO₂ . In fact, it is the formation of new covalent bonds between CO₂ and substrate molecules that successfully result in CO₂ solidly inserting into the products, and only four types of new CX bonds, including CH, CC, CN, and CO bonds, are observed in this exploration. An overview of recent progress in constructing CX bonds for CO₂ conversion catalyzed by various MOF catalysts is provided. The catalytic mechanism of generating different CX bonds is further discussed according to both structural features of MOFs and the interactions among CO₂ , substrates, as well as MOFs. The future opportunities and challenges in this field are also tentatively covered.

A novel crystalline azine-linked three-dimensional covalent organic framework for CO2 capture and conversion

A novel crystalline azine-linked three-dimensional covalent organic framework was rationally synthesized and exhibited excellent performance in CO₂ adsorption and conversion.

A rose bengal-functionalized porous organic polymer for carboxylative cyclization of propargyl alcohols with CO2

Rose bengal-functionalized polymer (RB-POP) supported Ag nanoparticles exhibited excellent performance for catalysing carboxylative cyclization of propargyl alcohols with CO₂.

Synthesis of tetronic acids from propargylic alcohols and CO2

A direct and practical synthesis of important tetronic acids from easily available propargylic alcohols and carbon dioxide is reported for the first time. This transition-metal-free transformation features high atom- and step-economy, mild reaction conditions, good functional group tolerance and high yield. Preliminary mechanistic studies suggest that the reaction proceeds via cyclization to give alkylidene cyclic carbonate, ring-opening and re-cyclization processes.

Efficient Ionic-Liquid-Promoted Chemical Fixation of CO2 into α-Alkylidene Cyclic Carbonates

The efficient conversion of CO₂ into value-added chemicals under metal-free conditions is of significant importance from the viewpoint of sustainable chemistry. In this work, ionic liquids (ILs) with different properties were used to promote the reaction between CO₂ and propargylic alcohol for the synthesis of α-alkylidene cyclic carbonates. The protic IL 1,8-diazabicyclo-[5.4.0]-7-undecenium 2-methylimidazolide ([DBUH][MIm]) was prepared by simple neutralization of the superbase with a weak proton donor and could efficiently promote the reactions in high yields. After the reactions, the IL was separated from the reaction mixtures by simply adding water, and then reused after drying without an observable decrease in the catalytic activity and selectivity. NMR spectroscopy and detailed density functional theory analysis were used to propose a reaction mechanism. Both the cation and anion of the IL played a key synergistic role in promoting the reaction. These findings may be useful for the rational design of novel metal-free and recyclable routes for the reaction between CO₂ and propargylic alcohols.

Synthesis of Carbonates from Alcohols and CO2

Alcohols are ubiquitous compounds in nature that offer modular building blocks for synthetic chemistry. Here we discuss the most recent development of different classes of alcohols and their coupling chemistry with carbon dioxide as to afford linear and cyclic carbonates, the challenges associated with their formation, and the potential of this chemistry to revive a waste carbon feed stock.

A simple and robust AgI/KOAc catalytic system for the carboxylative assembly of propargyl alcohols and carbon dioxide at atmospheric pressure

A simple, robust and economical AgI/KOAc system was developed for the carboxylative assembly of propargyl alcohols and CO₂ under mild conditions applying an unprecedentedly low level of 0.05 mol% Ag loading.