Integrative Photoreduction of CO2 with Subsequent Carbonylation: Photocatalysis for Reductive Functionalization of CO2.

Efficient conversion of CO2 into fuels and chemicals with solar energy would be promising, but also faces great challenge. In this context, we describe the photoreductive functionalization of CO2 to construct new C-C, C-N, and C-O bonds through the respective Pd-catalyzed Suzuki carbonylation, aminocarbonylation, and alkoxycarbonylation of aryl iodides with CO in situ generated through the photoreduction of CO2 . This protocol opens up an alternative avenue for CO2 utilization by harnessing solar energy.

Integration of CO2 Reduction with Subsequent Carbonylation: Towards Extending Chemical Utilization of CO2.

Currently, it still remains a challenge to amplify the spectrum of chemical fixation of CO2 , although enormous progress has been achieved in this field. In view of the widespread applications of CO in a myriad of industrial carbonylation processes, an alternative strategy is proposed in which CO2 reduction to CO is combined with carbonylation with CO generated ex situ, which affords efficiently pharmaceutically and agrochemically attractive molecules. As such, CO2 in this study was efficiently reduced by triphenysilane using CsF to CO in a sealed two-chamber reactor. Subsequently, palladium-catalyzed aminocarbonylation, carbonylative Sonogashira coupling of aryl iodides, and rhodium(I)-mediated Pauson-Khand-type reaction proceeded smoothly to yield amides, alkynones, and bicyclic cyclopentenones, respectively. Furthermore, the formed alkynones can further be successfully converted to a series of heterocycles, for example, pyrazoles, 3a-hydroxyisoxazolo[3,2-a]isoindol-8-(3aH)-one derivatives and pyrimidines in moderate yields. The striking features of this protocol include operational simplicity, high efficiency, and relatively broad application scope, which represents an alternative avenue for CO2 transformation.

AgI /TMG-Promoted Cascade Reaction of Propargyl Alcohols, Carbon Dioxide, and 2-Aminoethanols to 2-Oxazolidinones.

Chemical valorization of CO2 to access various value-added compounds has been a long-term and challenging objective from the viewpoint of sustainable chemistry. Herein, a one-pot three-component reaction of terminal propargyl alcohols, CO2 , and 2-aminoethanols was developed for the synthesis of 2-oxazolidinones and an equal amount of α-hydroxyl ketones promoted by Ag2 O/TMG (1,1,3,3-tetramethylguanidine) with a TON (turnover number) of up to 1260. By addition of terminal propargyl alcohol, the thermodynamic disadvantage of the conventional 2-aminoethanol/CO2 coupling was ameliorated. Mechanistic investigations including control experiments, DFT calculation, kinetic and NMR studies suggest that the reaction proceeds through a cascade pathway and TMG could activate propargyl alcohol and 2-aminoethanol through the formation of hydrogen bonds and also activate CO2 .

Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions.

As a renewable and abundant C1 resource possessing multiple attractive characteristics, such as low cost, nontoxicity, non-flammability, and easy accessibility, CO2 conversion into value-added chemicals and fuels can contribute to green chemistry and sustainable development. Since CO2 is a thermodynamically inert molecule, the activation of CO2 is pivotal for its effective conversion. In this regard, the formation of a transition-metal CO2 complex through direct coordination is one of the most powerful ways to induce the inert CO2 molecule to undergo chemical reactions. To date, numerous processes have been developed for efficient synthesis of cyclic carbonates from CO2 . On the basis of mechanistic understanding, we have developed efficient metal catalysts and green processes, including heterogeneous catalysis, and metal-free systems, such as ionic liquids, for cyclic carbonate synthesis. The big challenge is to develop catalysts that promote the reaction under low pressure (preferably at 1 bar). In this context, bifunctional catalysis is capable of synergistic activation of both the substrate and CO2 molecule, and thus, could render CO2 conversion smoothly under mild conditions. Alternatively, converting CO2 derivatives, that is, the captured CO2 as an activated species, would more easily take place at low pressure in comparison with gaseous CO2 . The aim of this Personal Account is to summarize versatile catalytic processes for cyclic carbonate synthesis from CO2 , including epoxide/CO2 coupling reaction, carboxylation of 1,2-diol with CO2 , oxidative cyclization of olefins with CO2 , condensation of vicinal halohydrin with CO2 , carboxylative cyclization of propargyl alcohols with CO2 , and conversion of the CO2 derivatives.

Equimolar carbon absorption by potassium phthalimide and in situ catalytic conversion under mild conditions.

Potassium phthalimide, with weak basicity, is an excellent absorbent for rapid carbon dioxide capture with almost equimolar absorption. This process is assumed to proceed through the potassium carbamate formation pathway, as supported by NMR spectroscopy, an in situ FTIR study, and computational calculations. Both the basicity and nucleophilicity of phthalimide salts have a crucial effect on the capture process. Furthermore, the captured carbon dioxide could more easily be converted in situ into value-added chemicals and fuel-related products through carbon capture and utilization, rather than going through a desorption process.