Bromine-Catalyzed Conversion of CO2 and Epoxides to Cyclic Carbonates under Continuous Flow Conditions

Organocatalyzed coupling of carbon dioxide with epoxides for the synthesis of cyclic carbonates: catalyst design and mechanistic studies

The coupling of carbon dioxide (CO₂) with epoxides with the formation of cyclic carbonates is a highly attractive 100% atom economic reaction. It represents a greener and safer alternative to the conventional synthesis of cyclic carbonates from diols and toxic phosgene.

New rht-Type Metal-Organic Frameworks Decorated with Acylamide Groups for Efficient Carbon Dioxide Capture and Chemical Fixation from Raw Power Plant Flue Gas

The combination of carbon dioxide capture and chemical fixation in a one-pot process is attractive for both chemists and governments. The cycloaddition of carbon dioxide with epoxides to produce cyclic carbonates is an atomic economical reaction without any side products. By incorporating acylamide to enhance the binding affinity toward CO₂, new rht-type metal-organic frameworks (MOFs) with (3, 28) and (3, 24) connected units were constructed. Zn-NTTA with two types of dinuclear paddlewheel building blocks-{Zn₂(OOC^-)₄} and {Zn₂(OOC^-)₃}. The high uptake of CO₂ (115.6 cm³·g^-1) and selectivity over N₂ (30:1) at 273 K indicated that these MOFs are excellent candidates for postcombustion CO₂ isolation and capture. The MOFs feature high catalytic activity, rapid dynamics of transformation and excellent stability with turnover number (TON) values up to 110 000 per paddlewheel unit after 5 × 6 rounds of recyclability, demonstrating that they are promising heterogeneous catalysts for CO₂ cyclo-addition to value-added cyclic carbonates. The cycloaddition of epoxides with wet gases demonstrated that the catalyst activity was not affected by moisture, and the indices of the PXRD patterns of the bulk samples filtered from the catalytic reaction revealed that the crystallinities were maintained. The combination of the selective capture and catalytic transformation in one-pot enables the use of a negative-cost feedstock-raw power plant flue gas without any separation and purification-revealing the broad prospects of such MOFs for practical CO₂ fixation in industry.

Hybrid Amine-Functionalized Graphene Oxide as a Robust Bifunctional Catalyst for Atmospheric Pressure Fixation of Carbon Dioxide using Cyclic Carbonates

An environmentally-benign carbocatalyst based on amine-functionalized graphene oxide (AP-GO) was synthesized and characterized. This catalyst shows superior activity for the chemical fixation of CO2 into cyclic carbonates at the atmospheric pressure. The developed carbocatalyst exhibits superior activity owing to its large surface area with abundant hydrogen bonding donor (HBD) capability and the presence of well-defined amine functional groups. The presence of various HBD and amine functional groups on the graphene oxide (GO) surface yields a synergistic effect for the activation of starting materials. Additionally, this catalyst shows high catalytic activity to synthesize carbonates at 70 °C and at 1 MPa CO2 pressure. The developed AP-GO could be easily recovered and used repetitively in up to seven recycle runs with unchanged catalyst activity.

Substrate-Controlled Product Divergence: Conversion of CO2 into Heterocyclic Products

Substituted epoxy alcohols and amines allow substrate-controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach results in an unusual scope of CO2-derived products by initial activation of CO2 through either the amine or alcohol unit, thus providing nucleophiles for intramolecular epoxy ring opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile-assisted ring-opening step following an SN i pathway, and a 5-exo-tet cyclization, thus leading to heterocyclic scaffolds.

Experimental and theoretical insights into binary Zn-SBA-15/KI catalysts for the selective coupling of CO2and epoxides into cyclic carbonates under mild conditions

Experimental and theoretical evidence gives insights into Zn-SBA-15/KI for selective coupling of CO₂and epoxides under mild conditions.

Economical synthesis of cyclic carbonates from carbon dioxide and halohydrins using K2CO3

Highly simple, economical and selective synthesis of five-membered cyclic carbonates was presented as a reaction of CO₂ and various 1,2-halohydrins using K₂CO₃ at 1 atm of CO₂ and 30 °C in DMF.

Cu(i)-catalyzed multicomponent cascade reactions of terminal alkynes, unactivated primary alkyl bromides, CO2 and NaN3

We have developed a mild, robust, and multicomponent cascade reaction for the synthesis of triazolo-fused dihydrooxazinones from terminal alkynes, unactivated primary alkyl bromides, carbon dioxide and sodium azide.

CO2 fixation at atmospheric pressure: porous ZnSnO3 nanocrystals as a highly efficient catalyst for the synthesis of cyclic carbonates

Self-assembled, ultra small, porous zinc stannate nanocrystals have been synthesized, which catalyzes the formation of cyclic carbonates from various epoxide and CO₂ under very mild reaction conditions.

Synthesis of cyclic carbonates from epoxides and carbon dioxide by using organocatalysts

The synthesis of cyclic carbonates through coupling of carbon dioxide with epoxides is 100 % atom economical and is already performed on an industrial scale. Its impact regarding the use of carbon dioxide as a renewable carbon source is expected to grow significantly in the near future, so that the development of efficient catalysts is of high interest in academia and industry. To improve the carbon footprint and sustainability of the cycloaddition reaction, the use of organocatalytic methods is a promising approach. Herein, available metal-free catalysts for the preparation of cyclic carbonates are described and elaborated concerning the overall sustainability of the process. Therefore, the required reaction conditions, as well as the activity of the catalysts and their reusability, are compared and evaluated. In addition to ammonium-, phosphonium-, or imidazolium-based single-component catalysts and their supported analogues, the growing field of research concerning dual catalysts are also discussed in detail.

Enantioselective small molecule synthesis by carbon dioxide fixation using a dual Brønsted acid/base organocatalyst

Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges one of the simplest biological approaches to catalysis-Brønsted acid/base activation-with this abundant reagent. We describe a metal-free small molecule catalyst that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine. Cyclic carbonates are formed enantioselectively.

Intermolecular proton transfer in cyclic carbonate synthesis from epoxide and carbon dioxide catalyzed by azaphosphatranes: a DFT mechanistic study

The activity of azaphosphatranes, novel types of non-metal and solvent-free catalysts for the synthesis of cyclic carbonates from epoxides and CO₂, is unraveled by DFT calculations.

Silanediol-catalyzed carbon dioxide fixation

Carbon dioxide is an abundant and renewable C1 source. However, mild transformations with carbon dioxide at atmospheric pressure are difficult to accomplish. Silanediols have been discovered to operate as effective hydrogen-bond donor organocatalysts for the atom-efficient conversion of epoxides to cyclic carbonates under environmentally friendly conditions. The reaction system is tolerant of a variety of epoxides and the desired cyclic carbonates are isolated in excellent yields.

Carbon dioxide as a protecting group: highly efficient and selective catalytic access to cyclic cis-diol scaffolds

The efficient and highly selective formation of a wide range of (hetero)cyclic cis-diol scaffolds using aminotriphenolate-based metal catalysts is reported. The key intermediates are cyclic carbonates, which are obtained in high yield and with high levels of diastereo- and chemoselectivity from the parent oxirane precursors and carbon dioxide. Deprotection of the carbonate structures affords synthetically useful cis-diol scaffolds with different ring sizes that incorporate various functional groups. This atom-efficient method allows the simple construction of diol synthons using inexpensive and accessible precursors and green metal catalysts and showcases the use of CO2 as a temporary protecting group.

Continuous flow synthesis of ketones from carbon dioxide and organolithium or Grignard reagents

We describe an efficient continuous flow synthesis of ketones from CO2 and organolithium or Grignard reagents that exhibits significant advantages over conventional batch conditions in suppressing undesired symmetric ketone and tertiary alcohol byproducts. We observed an unprecedented solvent-dependence of the organolithium reactivity, the key factor in governing selectivity during the flow process. A facile, telescoped three-step-one-flow process for the preparation of ketones in a modular fashion through the in-line generation of organometallic reagents is also established.

C60 fullerenol as an active and stable catalyst for the synthesis of cyclic carbonates from CO2 and epoxides

C₆₀ fullerenol was first found to be a highly active, selective and stable catalyst for cycloaddition of CO₂ and epoxides to produce various cyclic carbonates with excellent yields (89–99%). A solid/liquid interfacial hydrogen-bond assisted mechanism was proposed to account for its high efficiency.