An environmentally benign protocol of chemoselective transfer hydrogenation of C=C and C=O bonds with alkanols under base‐free conditions is developed by this study, wherein the cobalt‐ bidentate ...phosphine catalyst precursor is commercially available and the active low‐valent Co species could be generated in‐situ. For the conjugation enones, the vinyl group is selectively reduced, whereas with nonconjugated alkenones, the selectivity is changed to the carbonyl group. Besides, ortho‐alkenyl‐benzaldehydes/imines are well tolerated, and the reduction solely occurs at the C=O/C=N site with this protocol.
Low‐cost and sustainable: An environmentally benign protocol of Co‐bidentate phosphine complex‐catalyzed chemoselective transfer hydrogenation of C=C and C=O bonds with equivalent alkanols under base‐free conditions was developed.
A protocol for a CoII/N,N′,N′′‐trihydroxyisocyanuric acid (THICA)‐catalyzed aerobic oxidative esterification and amidation of aldehydes has been developed. Preliminary insight into the mechanism ...indicates that such an oxidative C−O/N cross‐coupling reaction proceeds by masking the aldehyde in a nucleophilic addition reaction with an alkoxy/amino source, thereby keeping the highly reactive formyl group from undesired oxidation. This protocol for the oxidative esterification and amidation of aldehydes proceeds through two different pathways that are characterized by the intrinsic nucleophilicity of the alkanol and amine substrates The former occurs in the presence of p‐CH3C6H4SO3H as a cocatalyst and orthoformates as the alkoxy sources, instead of alkanols, to efficiently afford the transient acetals. In contrast, the coupling of the more nucleophilic amines with aldehydes renders a readily accessible cross‐coupling reaction that occurs without any cocatalyst but is limited by the potential inhibition of THICA upon nucleophilic substitution by an amine. Consequently, only sterically hindered amines were tolerated in this catalytic system, whereas further condensation occurred in the presence of primary amines to lead to imines.
Through THICA and thin: A protocol for a CoII/N,N′,N′′‐trihydroxyisocyanuric acid (THICA) mediated aerobic oxidative esterification and amidation of aldehydes has been developed. A variety of esters and amides were obtained in moderate to excellent yields by using this one‐step approach.
Kidney stones are a common urinary system condition that can progress to kidney disease. Previous studies on the association between tea consumption and kidney stones are inconsistent. A ...cross-sectional study to investigate the association between tea consumption and kidney stones was conducted from 2013 to 2014 and recruited 9,078 northern Chinese adults. A total of 8,807 participants were included in the final analysis. Participants＇ prevalence of kidney stones was 1.07%, 1.73%, and 2.25% based on their tea consumption frecluencv of never, occasionally,
Realization of ideal molecular sieves, in which the larger gas molecules are completely blocked without sacrificing high adsorption capacities of the preferred smaller gas molecules, can ...significantly reduce energy costs for gas separation and purification and thus facilitate a possible technological transformation from the traditional energy‐intensive cryogenic distillation to the energy‐efficient, adsorbent‐based separation and purification in the future. Although extensive research endeavors are pursued to target ideal molecular sieves among diverse porous materials, over the past several decades, ideal molecular sieves for the separation and purification of light hydrocarbons are rarely realized. Herein, an ideal porous material, SIFSIX‐14‐Cu‐i (also termed as UTSA‐200), is reported with ultrafine tuning of pore size (3.4 Å) to effectively block ethylene (C2H4) molecules but to take up a record‐high amount of acetylene (C2H2, 58 cm3 cm−3 under 0.01 bar and 298 K). The material therefore sets up new benchmarks for both the adsorption capacity and selectivity, and thus provides a record purification capacity for the removal of trace C2H2 from C2H4 with 1.18 mmol g−1 C2H2 uptake capacity from a 1/99 C2H2/C2H4 mixture to produce 99.9999% pure C2H4 (much higher than the acceptable purity of 99.996% for polymer‐grade C2H4), as demonstrated by experimental breakthrough curves.
An ideal molecular sieve is realized for the highly efficient removal of C2H2 from C2H2/C2H4 (1:99) mixture, attributed to the optimized pore sizes to efficiently block C2H4 molecules, and strong binding sites to take up a record‐high amount of C2H2, thus simultaneously producing high purity C2H4 (99.9999%) with record C2H4 productivity of 87.5 mmol g−1 per cycle and recovery of C2H2 (97%).
A copper sulfate pentahydrate‐catalyzed intramolecular Friedel–Crafts reaction using an oxocarbenium species derived from a furan ring as the alkylating agent was developed for the first time. By ...using this protocol, spirofurooxindoles 9 with multi‐reactive sites were synthesized simply and concisely. In addition, selective hydrogenation of the endo‐cyclic double bond and full hydrogenation of the endo and exo‐cyclic double bonds of spirofurooxindoles 9 provided spirofurooxindoles 11 and 12, respectively.
Abstract
The effects of different elements on the mechanical properties and microstructure of pure Mg were studied by XRD, SEM, and tensile tests. The results show that with the addition of 1wt% Ca, ...Gd, La, and Y elements alone, different second-phase particles appear in the microstructure of Mg-1X. The addition of Gd and Y elements generates a small amount of Mg5Gd and Mg24Y5 particles, respectively. In contrast, the addition of the Ca element generates a large number of coarse Mg2Ca particles, and the addition of the La element generates a large number of fine and evenly distributed Mg12La particles. After extrusion, the extruded Mg-1X magnesium alloy shows a fine equiaxed recrystallization structure. All four alloys show bimodal texture distribution with deflection along the ED direction, and the texture deflected along the TD direction appears in Mg-1La alloy. The tensile test shows that the yield strength of MG-1La alloy is the highest when it is drawn along the ED direction. The yield strength of Mg-1La alloy is the lowest when it is drawn along TD.
Using a bis-triazolate ligand and tetrahedral Zn(II) ion, we synthesized a flexible porous coordination polymer functionalized with pairs of uncoordinated triazolate N-donors that can be used as ...guest chelating sites to give very high CO(2) adsorption enthalpy and CO(2)/N(2) selectivity. The dynamic CO(2) sorption behavior could be monitored well by single-crystal X-ray diffraction.
Compounds containing one carbon atom or no carbon-carbon bond (C1 compounds), such as trimethylamine and methanol, are important climate relevant gases in the atmosphere and play key roles in global ...warming. The ocean is a significant source or sink of such compounds, while the concentrations of trimethylamine and methanol in seawater remain largely unconstrained due to the analytical challenges involved. Therefore, it is necessary to establish a continuous, rapid and sensitive method for the determination of these compounds with high polarity, volatility or solubility at low seawater concentrations. Here we developed a purge and trap system, coupled to a gas chromatography equipped with dual nitrogen phosphorus detector (NPD) and flame ionization detector (FID) for the simultaneous online analysis of trimethylamine and methanol at nanomolar range using a small sample volume (~ 10 mL). The dual detection of trimethylamine and methanol with NPD or FID was achieved by installing a capillary flow splitter between the capillary column and detectors. After modification and optimization of the setup and conditions, excellent linearity (R 2 > 0.99) and repeatability (< 6%) were obtained for both compounds; the detection limits for trimethylamine and methanol were 0.3 nM and 17.6 nM, respectively. Using this method, water samples collected from coastal and open ocean were analyzed; trimethylamine and methanol concentrations ranged from 0.6 to 18.8 nM and 26.0 to 256.2 nM, respectively. Collectively, this method allowed for online, rapid, sensitive and simultaneous quantification of trace trimethylamine and methanol concentrations with low-cost instrumentation and small sample volume, which makes it promising for further application in volatile compounds analysis in marine environments.
Doping asymmetry is a pervasive issue in wide band gap semiconductors. We demonstrated that γ-CuCl is one of them with an intrinsic p-type semiconductor by first-principles calculations. The valence ...band maximum of γ-CuCl is dominated by the antibonding state of Cu-3d and Cl-3p, resulting in a high energy position. We further find that Cu vacancy has a relatively low diffusion barrier in addition to its low formation energy, implying that the long-standing n-type conductivity is hard to realize in γ-CuCl even with non-equilibrium approaches.
•γ-CuCl is an intrinsic p-type semiconductor owing to the low formation energy of Cu vacancy.•The low diffusion barrier of Cu vacancy make the long-standing n-type conductivity cannot be realized in γ-CuCl.•The microscopic origin of doping asymmetry in γ-CuCl is discussed.
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