查看更多>>摘要：Sustainability requires that we reuse spent carbon sources from CO2 emissions to generate new products and materials. In this regard, carbon capture is a necessary requirement for avoiding disastrous climate changes. Hence, accompanying carbon capture technology is the need for developing low-energy processes for carbon dioxide utilization. The coupling of three-membered cycle ethers, aka oxiranes or epoxides, with carbon dioxide to provide useful cyclic carbonates or polymeric materials represents a viable approach to aid in addressing this issue. This results from the recalcitrant nature of CO2 being overcome by the energy released during the epoxide ring opening process, ～114 kJ mol?1. Noteworthy, in this instance carbon dioxide does not undergo reduction. Consideration of the origin of the epoxide is also of importance as epoxides derived from renewable resources can be beneficial to a sustainable process. Consistent with the concept of being Green, it is also of value that the catalysis employed in these transformations be biocompatible, especially for the production of materials used in biomedical science. In this review we wish to present recent developments in the catalytic chemistry for coupling of carbon dioxide and epoxides to afford either cyclic or polymeric carbonates. Focus will be centered on new metal catalysis, especially for sequential addition of mixtures of monomers, and the use of organocatalysts for carrying out these chemical conversions.
查看更多>>摘要：In recent years, the growing awareness of the harmfulness of chemicals to the environment has resulted in the development of green and sustainable technologies. The compromise between economy and environmental requirements is based on the development of new efficient and green solutions. Supramolecular deep eutectic solvents (SUPRADESs), a new deep eutectic solvent (DES) subclass characterized by inclusion properties, are a fresh discovery that could have a significant impact on the development of green chemistry. SUPRADESs known in the literature consist of green ingredients, their physicochemical properties are similar to those of conventional DESs, and their supramolecular nature allows for selective binding of numerous chemical compounds – for many applications SUPRADESs show much higher efficiency compared with DESs. Because of the inclusion of cyclodextrins in their structure, these solvents are able to bind to many compounds through the formation of hydrogen bonds (typical of DESs) and at the same time interact with them in a host–guest mechanism. The combination of the environmentally friendly properties of DESs with those of cyclodextrins could be a breakthrough in the context of green chemistry. This review paper summarizes the available knowledge about SUPRADESs – their composition, physicochemical properties, applications and perspectives. SUPRADESs described in the work are fully green, non-toxic, and biodegradable solvents which are capable of efficiently absorbing many substances. So far, few SUPRADESs are known, but some of them are classified as low melting mixtures (LMM). It is very important to systematize the data available on these green solvents and properly classify them. We hope that identifying their potential and green characteristics will support further promising discoveries.
查看更多>>摘要：A versatile photochemical ring contraction is reported for the synthesis of oxetanes under catalyst-free conditions. The reaction is enabled by the use of 2,5-dihydrofurans and diazo compounds under visible light irradiation, delivering functionalized 3-vinyloxetanes as major products. The outstanding features of this protocol include mild reaction conditions, operational simplicity and scalability, as well as excellent functional-group tolerance. DFT calculations indicate that the reaction may proceed through the formation of an oxonium ylide intermediate followed by a diradical-mediated rearrangement and cyclization.
查看更多>>摘要：Renewable and abundant carbohydrates are promising feedstocks for producing valuable chemicals. Here we report a highly efficient Zr-catalysed conversion of xylose and acetylacetone (acac) to a new type of bisfuranic monomer, 1-(4-((4-acetyl-5-methylfuran-2-yl)methyl)-2-methylfuran-3-yl)ethenone (MFE). The formation of MFE stems from the intermediate obtained through the nucleophilic addition of acac to xylose. Under optimized conditions (microwave irradiation, 140 °C, 24 min, NaI as an additive), MFE is obtained in near-quantitative yield (98%). Importantly, the reaction selectivity can be tuned by the inclusion of an additive. When NaCl is used, the reaction gives 3-(furan-2-ylmethylene)pentane-2,4-dione (FMPD, 55%), a jet-fuel precursor, and MFE (30%) with a total carbon yield of 85%. To the best of our knowledge, this is the first report on straightforward xylose transformation to a bisfuranic compound with excellent carbon efficiency. This Garcia Gonzalez (GG) reaction inclusive strategy is remarkable and could lead to many innovations in bio-based polymer synthesis.
查看更多>>摘要：An electrochemical method for the synthesis of 2-aminothiazoles via aryl ring construction using enaminones and thioureas is reported. The cascade enamine C–H thiolation and C–N amination constitutes a major transformation for the thiazole ring formation. Moreover, a simple modification of electrochemical conditions enables the tunable dearomatization of the thiazole ring via vicinal dialkoxylation, leading to the synthesis of 4,5-dialkoxyl thiazolines bearing a quaternary carbon center with excellent diastereoselectivity.
查看更多>>摘要：Glycolic acid is an important building block of biodegradable polymers. Herein, we report an efficient selective and atom-economical approach for the synthesis of glycolic acid based on a catalytic C–C coupling reaction of the inexpensive C1 compound formaldehyde followed by selective oxidation. The developed approach relies on an evolved formolase with improved activity at a high formaldehyde concentration (up to 1 M) and controlled oxidation by the oxidant, sodium chlorite or H2O2. Kinetic characterization, molecular dynamics simulation and binding free energy calculation demonstrated that the identified amino acid substitutions of the evolved formolase stabilize the first reaction intermediate state TPP-FA (thiamine pyrophosphate-formaldehyde) and the second intermediate state TPP-GA (thiamine pyrophosphate-glycolaldehyde), which is beneficial for the C–C coupling product generation, especially C2 GA at a high concentration of formaldehyde. The chemoenzymatic approach established in this work provides a new opportunity to manufacture monomers of biodegradable polymers from CO2 derivatives.
Nguyen Chi VanYeh Jyun-YiTran Thuan VanWu Kevin C.-W....
7页
查看更多>>摘要：Here, we report the one-pot conversion of saccharides to 2,5-dimethyl furan (DMF) using a combination of two noble-metal-free catalysts (i.e., P-UiO-66 and Ni–Co@NC). In this catalytic bioconversion, the saccharide was first converted to 5-hydroxymethylfurfural (HMF) over the P-UiO-66 catalyst containing strong acidic sites, and then the so-formed HMF was hydrogenated and hydrogenolyzed to DMF over the Ni–Co@NC catalyst, resulting in a high yield of >80%.
NSTL
Royal Soc Chemistry