Carbene-Catalyzed Atroposelective Construction of Chiral Diaryl Ethers.

Atropoisomeric chemotypes of diaryl ethers-related scaffolds are prevalent in naturally active compounds. Nevertheless, there remains considerable research to be carried out on the catalytic asymmetric synthesis of these axially chiral molecules. In this instance, we disclose an N-heterocyclic carbene (NHC)-catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde-containing diaryl ethers. NHC desymmetrization produces axially chiral diaryl ether atropisomers with high yields and enantioselectivities in moderate circumstances. Chiral diaryl ether compounds may be precursors for highly functionalized diaryl ethers with bioactivity and chiral ligands for asymmetric catalysis.

In situ H2 O2 Generation and Corresponding Pollutant Removal Applications: A Review.

Catalytic hydrogen peroxide (H2 O2 ) generation from oxygen and water enables a sustainable environment to operate in an effective and green energy-to-chemical conversion way, which has attracted increasing interest in the fields of energy production and environment treatment. In light of this, tremendous progresses and developments have been made during the past decades in catalytic H2 O2 production for pollutant removal from three perspectives including photocatalysis, electrocatalysis or chemical activation. Herein, we critically review the state-of-the-art developments over various procedures of H2 O2 generation and its further application, with the existence of photocatalysts, electrocatalysts, and catalysts, respectively. Benefiting from extensively experimental and theoretical investigations, the performance and stability of H2 O2 generation and its utilization can be maneuvered by devising catalytic platform based on numerous catalysts with predominant electronic, chemical and physical properties, which endow the catalysts with efficient electrons transportation, abundant active sites, and sufficient oxygen adsorption for H2 O2 generation. Furthermore, this review also discusses the formation mechanism of H2 O2 by 2e-ORR and 2e-WOR, as well as its functional process of activating and removing pollutants, and summarizes the design principles of various catalysts by focusing on the formation of H2 O2 . We finally highlight the specific challenges and prospects related to the utilization of catalysts and envision the possible future development trends in the fields of pollutant removal.

Iridium-Catalyzed Asymmetric Allylic Substitution Reaction of 4-Hydroxypyran-2-one.

Pyranones have raised great concerns owing to their considerable applications in a variety of sectors. However, the development of direct asymmetric allylation of 4-hydroxypyran-2-ones is still restricted. Herein, we present an effective iridium-catalyzed asymmetric functionalization technique for the synthesis of 4-hydroxypyran-2-one derivatives over direct and efficient catalytic asymmetric Friedel-Crafts-type allylation by using allyl alcohols. The allylation products could be obtained with good to high yields (up to 96%) and excellent enantioselectivities (>99% ee). Therefore, the disclosed technique provides a new asymmetric synthetic strategy to explore pyranone derivatives in depth, thus providing an interesting approach for global application and further utilization in organic synthesis and pharmaceutical chemistry.

A Dynamic Kinetic Resolution Approach to Axially Chiral Diaryl Ethers by Catalytic Atroposelective Transfer Hydrogenation.

Diaryl ethers are widespread in biologically active compounds, ligands and catalysts. It is known that the diaryl ether skeleton may exhibit atropisomerism when both aryl rings are unsymmetrically substituted with bulky groups. Despite recent advances, only very few catalytic asymmetric methods have been developed to construct such axially chiral compounds. We describe herein a dynamic kinetic resolution approach to axially chiral diaryl ethers via a Brønsted acid catalyzed atroposelective transfer hydrogenation (ATH) reaction of dicarbaldehydes with anilines. The desired diaryl ethers could be obtained in moderate to good chemical yields (up to 79 %) and high enantioselectivities (up to 95 % ee) under standard reaction conditions. Such structural motifs are interesting precursors for further transformations and may have potential applications in the synthesis of chiral ligands or catalysts.

Emerging Cocatalysts on g-C3 N4 for Photocatalytic Hydrogen Evolution.

Over the past few decades, graphitic carbon nitride (g-C3 N4 ) has arisen much attention as a promising candidate for photocatalytic hydrogen evolution reaction (HER) owing to its low cost and visible light response ability. However, the unsatisfied HER performance originated from the strong charge recombination of g-C3 N4 severely inhibits the further large-scale application of g-C3 N4 . In this case, the utilization of cocatalysts is a novel frontline in the g-C3 N4 -based photocatalytic systems due to the positive effects of cocatalysts on supressing charge carrier recombination, reducing the HER overpotential, and improving photocatalytic activity. This review summarizes some recent advances about the high-performance cocatalysts based on g-C3 N4 toward HER. Specifically, the functions, design principle, classification, modification strategies of cocatalysts, as well as their intrinsic mechanism for the enhanced photocatalytic HER activity are discussed here. Finally, the pivotal challenges and future developments of cocatalysts in the field of HER are further proposed.

Efficient Solar Light Harvesting CdS/Co9 S8 Hollow Cubes for Z-Scheme Photocatalytic Water Splitting.

Hollow structures with an efficient light harvesting and tunable interior component offer great advantages for constructing a Z-scheme system. Controlled design of hollow cobalt sulfide (Co9 S8 ) cubes embedded with cadmium sulfide quantum dots (QDs) is described, using hollow Co(OH)2 as the template and a one-pot hydrothermal strategy. The hollow CdS/Co9 S8 cubes utilize multiple reflections of light in the cubic structure to achieve enhanced photocatalytic activity. Importantly, the photoexcited charge carriers can be effectively separated by the construction of a redox-mediator-free Z-scheme system. The hydrogen evolution rate over hollow CdS/Co9 S8 is 134 and 9.1 times higher than that of pure hollow Co9 S8 and CdS QDs under simulated solar light irradiation, respectively. Moreover, this is the first report describing construction of a hollow Co9 S8 based Z-scheme system for photocatalytic water splitting, which gives full play to the advantages of light-harvesting and charges separation.

[The clinical and CT two-phase imaging features of bronchial-pulmonary arterial fistula].

OBJECTIVE: To study the clinical features of bronchial-pulmonary arterial fistula, and to analyze its imaging features. METHODS: In continuous five months, 502 patients for pulmonary angiography were analyzed by pulmonary/aortic arterial two-phase scanning. The 128-slice MSCT (Siemens Definition AS 128) was used with the following parameters: the speed of 0.5 s/weeks, the collimator width of 64 × 0.6 mm, the pitch of 0.9, the tube voltage of 120 kV, the contrast agent of 300 mg/ml (1.2 ml/kg) , and the flow rate of 4.3 ml/s. Automatic trigger technology was used, while the threshold of the main pulmonary artery trunk was set to 80 HU. After 4 s delay, the pulmonary-arterial phase was scanned for 3-5 s. Then, the aortic-arterial phase was taken after 12 s. Finally, the clinical features and CTA two-phase images were analyzed by two radiologists, respectively. The diagnozied criteria of CTA images for bronchial-pulmonary arterial fistula were as following.In pulmonary/aortic arterial two-phase scanning, pulmonary artery or aortic artery could be displayed, respectively. The filling defect of fistula's pulmonary artery was observed in pulmonary arterial phase. However, the filling defect of fistula's pulmonary artery had significant filling in aortic arterial phase, with the similar density intensity of aortic artery.In addition, the thicken bronchial artery were observed in the fistula area. CLINICAL FEATURES: In all 502 patients, 65 positive cases of the bronchial-pulmonary arterial fistula included 37 male cases and 28 female cases with ages from 45 to 83 years (69 ± 11). The clinical symptoms included hemoptysis (32%), anhelation (69%), hypoxia (66%), the raise of D2 dimer (70%), and pulmonary hypertension (64%). CTA two-phase images features: In the pulmonary-arterial phase, the intensity difference of pulmonary/aortic was [322 ± 122 (100-751)] HU. The local filling defect in the proximal pulmonary artery (12%) and the filling defect in the whole pulmonary artery (88%) were observed in 65 positive cases.In the aortic-arterial phase, the intensity difference of pulmonary/aortic was [251 ± 89 (85-428)] HU. The local enhancement in the proximal pulmonary artery (24%) and the enhancement in the whole pulmonary artery (76%) were observed in 58 positive cases. The visible thicken bronchial artery were observed in the fistula area of all cases.In 65 cases of bronchial-pulmonary arterial fistula, the fistula lesions contained 56 cases of lung lesions (including 35 cases of honeycomb lung, 16 cases of atelectasis, and 3 cases of chronic mass-like pneumonia) and 9 cases of vascular lesions (including 4 cases of chronic pulmonary artery embolism, 3 cases of congenital vascular malformation, 1 case of pulmonary arthritis, and 1 case of pulmonary artery aneurysm). 437 cases of non bronchial-pulmonary arterial fistula had 4 cases of of vascular lesions and 76 cases of lung lesions. There were significant statistic difference between the fistula and vascular lesions or lung lesions (the value of χ(2): 37.51 or 165.11, all values of P < 0.001). CONCLUSION: The disease of bronchial-pulmonary arterial fistula usually occurred in the chronic pneumonia and the pulmonary vascular lesions. The CT pulmonary/aortic arterial two-phase scanning could detect the homodynamic changes to diagnosis this disease correctly. The pulmonary embolism need be differentiated.

Order-Disorder Engineering of Carbon Nitride for Photocatalytic H2O2 Generation Coupled with Pollutant Removal.

Highly crystalline carbon nitride (CCN), benefiting from the reduced structural imperfections, enables improved electron-hole separation. Yet, the crystalline phase with insufficient inherent defects suffers from a poor performance toward the reaction intermediate adsorption with respect to the amorphous phase. Herein, a crystalline-amorphous carbon nitride (CACN) with an isotype structure was constructed via a two-step adjacent calcination strategy. Through specific oxygen etching and crystallization, the formation of a built-in electric field at the interface could drive charge transfer and separation, thus promoting photoredox reaction. As expected, the optimized CACN exhibited a H2O2 generation efficiency as high as 2.15 mM gcat-1 h-1, paired with a promoted pollutant degradation efficiency, which outperform its crystalline (CCN) and amorphous [amorphous carbon nitride (ACN)] counterparts. The detailed electron/hole transportation via a built-in electronic field and free radical formation based on the enhanced adsorption of oxygen were considered, and the synchronous reaction pathway was carried out. This work paves a novel pathway for the synthesis of carbon nitride with an isotype structure from the perspective of interfacial engineering.

Recent Progress of Metal Sulfide Photocatalysts for Solar Energy Conversion.

Artificial photosynthetic solar-to-chemical cycles enable an entire environment to operate in a more complex, yet effective, way to perform natural photosynthesis. However, such artificial systems suffer from a lack of well-established photocatalysts with the ability to harvest the solar spectrum and rich catalytic active-site density. Benefiting from extensive experimental and theoretical investigations, this bottleneck may be overcome by devising a photocatalytic platform based on metal sulfides with predominant electronic, physical, and chemical properties. These tunable properties can endow them with abundant active sites, favorable light utilization, and expedited charge transportation for solar-to-chemical conversion. Here, it is described how some vital lessons extracted from previous investigations are employed to promote the further development of metal sulfides for artificial photosynthesis, including water splitting, CO2 reduction, N2 reduction, and pollutant removal. Their functions, properties, synthetic strategies, emerging issues, design principles, and intrinsic functional mechanisms for photocatalytic redox reactions are discussed in detail. Finally, the associated challenges and prospects for the utilization of metal sulfides are highlighted and future development trends in photocatalysis are envisioned.

Hierarchical macro-mesoporous g-C3N4 with an inverse opal structure and vacancies for high-efficiency solar energy conversion and environmental remediation.

Hierarchical macro-mesoporous structures with an efficient mass transfer and light harvesting offer great advantages for photocatalysis. Nitrogen vacancy modified ordered hierarchical macro-mesoporous g-C3N4 (Nv MM CN) was fabricated by a dual-templating method combining an ordered SiO2 colloidal crystal and NH4Cl. The as-prepared Nv MM CN was applied for photocatalytic degradation of antibiotics and production of hydrogen. Nv MM CN showed 27 times higher photocatalytic degradation efficiency and 7.5 times higher hydrogen production than bulk g-C3N4 (Bulk CN) under visible light irradiation. The 3D well interconnected macro-mesoporous structure and the porous system accelerated adsorption as well as the reaction rate and the inverse opal photonic crystals provided multiple scattering effects to strengthen light absorption. Meanwhile, the nitrogen vacancy introduced acted as a separation center to capture electrons or holes to improve the separation efficiency of charges. This efficient, stable, and environmentally friendly visible light-driven Nv MM CN may be an alternative for effective implementation in wide-ranging energy and environmental applications.

A robust and efficient catalyst of CdxZn1-xSe motivated by CoP for photocatalytic hydrogen evolution under sunlight irradiation.

CdxZn1-xSe/CoP composites have been well studied as effervescent photocatalysts for H2 evolution. These composites are highly efficient at 45.1 mmol h-1 g-1 and have a high quantum yield of 11.8% at ∼520 nm. The tunable energy band of CdxZn1-xSe facilitates photo-electrons transferring to CoP via chemical bonds between components. Advances in CdxZn1-xSe/CoP for photocatalytic H2 evolution provide a new strategy for future splitting of seawater.