4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

Catalysis for the valorization of exhaust carbon: from CO2 to chemicals, materials, and fuels. technological use of CO2.

The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO2 in the atmosphere. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO2 buildup. This review covers six important CO2 transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO2, its synthetic reactions and their possible role in future CO2 mitigation schemes that has to match the scale of man-made CO2 in the atmosphere, which rapidly approaches 1 teraton.

The teraton challenge. A review of fixation and transformation of carbon dioxide

The fascinating story of olefin (or alkene) metathesis (eq
1) began almost five decades ago, when Anderson and
Merckling reported the first carbon-carbon double-bond
rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

https://core.ac.uk/download/pdf/4884240.pdf

Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts.

Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.

/pdf/sustainable-polymers-from-renewable-resources-3zc6tmi7nv.pdf

Sustainable polymers from renewable resources

This comprehensive tutorial review focuses on well-defined cobalt complexes that serve as homogeneous catalysts for the production of polycarbonates and cyclic carbonates from the coupling of carbon dioxide and epoxides. Special considerations are given to the mechanistic pathways involved in these processes.

Cobalt catalysts for the coupling of CO2 and epoxides to provide polycarbonates and cyclic carbonates

The use of carbon dioxide as a carbon source for the synthesis of organic chemicals can contribute to a more sustainable chemical industry. Because CO2 is such a thermodynamically stable molecule, few effective catalysts are available to facilitate this transformation. Currently, the major industrial processes that convert CO2 into viable products generate urea and hydroxybenzoic acid. One of the most promising new technologies for the use of this abundant, inexpensive, and nontoxic renewable resource is the alternating copolymerization of CO2 and epoxides to provide biodegradable polycarbonates, which are highly valuable polymeric materials. Because this process often generates byproducts, such as polyether or ether linkages randomly dispersed within the polycarbonate chains and/or the more thermodynamically stable cyclic carbonates, the choice of catalyst is critical for selectively obtaining the expected product.In this Account, we outline our efforts to develop highly active Co(III)-based catalysts fo...

CO2 Copolymers from Epoxides: Catalyst Activity, Product Selectivity, and Stereochemistry Control

Asymmetric, regio- and stereoselective alternating copolymerization of CO(2) and racemic aliphatic epoxides proceeds effectively under mild temperature and pressure by using a binary catalyst system of a chiral tetradentate Schiff base cobalt complex [SalenCo(III)X] as the electrophile in conjunction with an ionic organic ammonium salt or a sterically hindered strong organic base as the nucleophile. The substituent groups on the aromatic rings, chiral diamine backbone, and axial X group of the electrophile, as well as the nucleophilicity, leaving ability, and coordination ability of the nucleophile, all significantly affect the catalyst activity, polymer selectivity, enantioselectivity, and stereochemistry. A bulky chiral cyclohexenediimine backbone complex [SalcyCo(III)X] with an axial X group of poor leaving ability as the electrophile, combined with a bulky nuclephile with poor leaving ability and low coordination ability, is an ideal binary catalyst system for the copolymerization of CO(2) and a racemic aliphatic epoxide to selectively produce polycarbonates with relatively high enantioselectivity, >95% head-to-tail connectivity, and >99% carbonate linkages. A fast copolymerization of CO(2) and epoxides was observed when the concentration of the electrophile or/and the nucleophile was increased, and the number of polycarbonate chains was proportional to the concentration of the nucleophile. Electrospray ionization mass spectrometry, in combination with a kinetic study, showed that the copolymerization involved the coordination activation of the monomer by the electrophile and polymer chain growth predominately occurring in the nucleophile. Both the enantiomorphic site effect resulting from the chiral electrophile and the polymer chain end effect mainly from the bulky nucleophile cooperatively control the stereochemistry of the CO(2)/epoxide copolymerization.

http://www.polymer.cn/UploadFile/ResearchPic/Polymer2005_2006927113504369.pdf

Design of highly active binary catalyst systems for CO2/epoxide copolymerization: polymer selectivity, enantioselectivity, and stereochemistry control.

https://www.onlinelibrary.wiley.com/doi/epdf/10.1002/anie.200453998

Highly active, binary catalyst systems for the alternating copolymerization of CO2 and epoxides under mild conditions.

Thermal stability of CO2 adducts of N-heterocyclic carbenes (NHCs) was studied by means of in situ FTIR method with monitoring of the nu(CO2) region of the infrared spectra under various conditions. 1,3-Bis(2,6-diisopropylphenyl)imidazolinium-2-carboxylate (SIPr-CO2) shows higher thermal stability compared with 1,3-bis(2,6-diisopropylphenyl)imidazolium-2-carboxylate (IPr-CO2). The presence of free CO2 can significantly inhibit the decomposition of NHC-CO2 adducts, while the addition of an epoxide such as propylene oxide has a negative effect on stabilizing these adducts. As zwitterionic compounds, NHC-CO2 adducts were also proved to be effective organic catalysts for the coupling reaction of CO2 and epoxides to afford cyclic carbonates, for which a possible mechanism was proposed. Among these NHC-CO2 adducts, the relatively unstable IPr-CO2 exhibits the highest catalytic activity. The presence of an electrophile such as SalenAlEt could greatly improve the catalytic activity of IPr-CO2 due to intermolecular cooperative catalysis of the binary components.

Xiao-Bing Lu

Papers

Cobalt catalysts for the coupling of CO2 and epoxides to provide polycarbonates and cyclic carbonates

CO2 Copolymers from Epoxides: Catalyst Activity, Product Selectivity, and Stereochemistry Control

Design of highly active binary catalyst systems for CO2/epoxide copolymerization: polymer selectivity, enantioselectivity, and stereochemistry control.

Highly active, binary catalyst systems for the alternating copolymerization of CO2 and epoxides under mild conditions.

CO2 Adducts of N-Heterocyclic Carbenes: Thermal Stability and Catalytic Activity toward the Coupling of CO2 with Epoxides