Copper-Catalyzed and Proton-Directed Selective Hydroxymethylation of Alkynes with CO2.

An intriguing strategy for copper-catalyzed hydroxymethylation of alkynes with CO2 and hydrosilane was developed. Switched on/off a proton source, for example, t BuOH, direct hydroxymethylation and reductive hydroxymethylation could be triggered selectively, delivering a series of allylic alcohols and homobenzylic alcohols, respectively, with high levels of Z/E, regio- and enantioselectivity. Such a selective synthesis is attributed to the differences in response of vinylcopper intermediate to proton and CO2 . The protonation of vinylcopper species is demonstrated to be prior to hydroxymethylation, thus allowing a diversion from direct alkyne hydroxymethylation to reductive hydroxymethylation in the presence of suitable proton.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble-Metal-Free [Zn116 ] Nanocages.

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metal-free MOFs catalysts. Here, a giant and lantern-like [Zn116 ] nanocage in zinc-tetrazole 3D framework [Zn22 (Trz)8 (OH)12 (H2 O)9 ⋅8 H2 O]n Trz=(C4 N12 O)4- (1) was obtained and structurally characterized. It consists of six [Zn14 O21 ] clusters and eight [Zn4 O4 ] clusters. To our knowledge, this is the highest-nuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2 , exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble-metal-free MOFs catalyst for the cyclization of propargylic amines with CO2 . DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

Ionic Liquid-Promoted Three-Component Domino Reaction of Propargyl Alcohols, Carbon Dioxide and 2-Aminoethanols: A Thermodynamically Favorable Synthesis of 2-Oxazolidinones.

To circumvent the thermodynamic limitation of the synthesis of oxazolidinones starting from 2-aminoethanols and CO2 and realize incorporation CO2 under atmospheric pressure, a protic ionic liquid-facilitated three-component reaction of propargyl alcohols, CO2 and 2-aminoethanols was developed to produce 2-oxazolidinones along with equal amount of α-hydroxyl ketones. The ionic liquid structure, reaction temperature and reaction time were in detail investigated. And 15 mol% 1,5,7-triazabicylo[4.4.0]dec-5-ene ([TBDH][TFE]) trifluoroethanol was found to be able to synergistically activate the substrate and CO2, thus catalyzing this cascade reaction under atmospheric CO2 pressure. By employing this task-specific ionic liquid as sustainable catalyst, 2-aminoethanols with different substituents were successfully transformed to 2-oxazolidinones with moderate to excellent yield after 12 h at 80 °C.

PPh3-Promoted Direct Deoxygenation of Epoxides to Alkenes.

Deoxygenation of epoxides into alkenes is one of the most important strategies in organic synthesis, biomass conversions, and medicinal chemistry. Although metal-catalyzed direct deoxygenation provides one of the most commonly encountered protocols for the conversion of epoxides to alkenes, the requirement of expensive catalysts and extra reductants has largely limited their universal applicability. Herein, we report an efficient PPh3-promoted metal-free strategy for deoxygenation of epoxides to generate alkene derivatives. The success of deoxyalkenylation of epoxides bearing a wide range of functional groups to give terminal, 1,1-disubstituted, and 1,2-disubstituted alkenes manifests the powerfulness and versatility of this strategy. Moreover, gram-scale synthesis with excellent yield and modification of biologically active molecules exemplifies its generality and practicability.

Nickel-Catalyzed Stereoselective Alkenylation of Ketones Mediated by Hydrazine.

The direct conversion of naturally abundant carbonyl compounds provides a powerful platform for the efficient synthesis of valuable chemicals. In particular, the conversion of ketones to alkenes is a commonly encountered chemical transformation, often achieved via the multistep Shapiro reaction with tosylhydrazone and over stoichiometric organolithium or Grignard reagent. Herein, we report an earth abundant nickel-catalyzed alkenylation of naturally abundant methylene ketones to afford a wide range of alkene derivatives, mediated by hydrazine. The protocol features a broad substrate scope (including alkyl ketones, aryl ketones, and aldehydes), good functional group compatibility, mild reaction conditions, water tolerance, and only environmentally friendly N2, H2, and H2O as theoretical byproducts. Moreover, gram-scale synthesis with good yield and generation of pharmaceutical intermediates highlighted its practical applicability.

Tuning of Ionic Second Coordination Sphere in Evolved Rhenium Catalyst for Efficient Visible-Light-Driven CO2 Reduction.

Developing an efficient and easy-to-handle strategy in designing catalysts for CO2 reduction into CO by harnessing sunlight is a promising project. Here, a facile strategy was developed to design a Re catalyst modified with an ionic secondary coordination sphere for photoreduction of CO2 to CO by visible light. By adding ionic liquids or tuning a different ionic secondary coordination sphere, it was discovered that an outstanding optical property, other than CO2 absorption ability or the ability to dissociation of chloride anion, is the prerequisite for catalyst design. Accordingly, a novel Re catalyst, {Re[BpyMe(tris(2-hydroxyethyl)amine)](CO)3 Cl}Br (Re-THEA), was designed, screened, and resulted in a relative high quantum yield (up to 34 %) for visible-light-induced CO2 reduction with a single-molecule system. DFT calculations, combined with experimental outcomes, suggested the pendant ionic tris(2-hydroxyethyl)amino (THEA) group on Re-THEA can enhance visible-light absorption, stabilize reaction intermediates, and suppress the Re-Re dimer formation.

Enhanced visible light photocatalytic activity of N, F-codoped TiO2 powders with high thermal stability.

Doping non-metals onto TiO2 has been regarded as a promising way to gain a more effective photocatalyst. In this paper, N, F-codoped TiO2 was synthesized by the sol-gel method, demonstrating both high adsorption capacity and high photocatalytic activity under visible light irradiation. Samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and UV-visible diffuse reflectance spectra (UV-vis DRS). The results show that N, F-codoping can reduce the impact of calcination temperature on the structure and morphology of the sample, resulting in the sample exhibiting good thermal stability, even when the calcination temperature changes in a large range, instead of rutile, the anatase around 20 nm is the only phase in N, F-codoped samples. It can be clearly observed from the SEM images that N, F-codoped samples calcined at different temperatures are in the state of scattered particles with small size and good dispersed property. And it is vivid that the absorption intensity of N, F-codoped TiO2 samples in the visible light range increases substantially in DRS. According to the result of photocatalytic activity experiment, N, F-codoped TiO2 samples calcined at 973 K exhibited the highest degradation rate for Methylene Blue.

Ionic Liquids Catalysis for Carbon Dioxide Conversion With Nucleophiles.

Carbon dioxide, as a promising C1 synthon, has attracted great interest in organic synthesis. Due to the thermodynamic stability and kinetic inertness of CO2, developing efficient strategies for CO2 activation and subsequent conversion is very crucial. In this context, Ionic liquids (ILs) show great potential for capturing and activating CO2 owing to their unique structures and properties, making them become ideal alternatives to volatile organic solvents and/or catalysts for CO2 transformation. This minireview aims at summarizing ILs-promoted reactions of CO2 with N-nucleophiles (primary amines)/O-nucleophiles (primary alcohols, water). Two catalytic systems i.e., metal/ILs binary systems such as Cu/ILs systems and Ag/ILs systems as well as single ILs systems including anion-functionalized ILs and bifunctionalized ILs have been developed for CO2 catalytic conversion, for instance, carboxylative cyclization of nucleophiles e.g., propargylic alcohols, amines, 2-aminobenzonitriles and o-aminobenzenethiol, and formylation of amines or 2-aminothiophenols with hydrosilanes to afford various value-added chemicals e.g., cyclic carbamates, unsymmetrical organic carbonates, α-hydroxyl ketones, and benzimidazolones. In a word, IL could provide a powerful tool for efficient CO2 utilization.

Release and kinetics of arsenic and plumbum in the Songhua River surficial sediments.

To estimate the pollution of As and Pb in the Songhua River which flows through the major rice-producing regions in China, the present study investigated the level and release of As and Pb in surficial sediments which collected from nine sites in Songhua River (M1-M9). The concentration of As and Pb was ranged as follows: As = 3.104~15.01 µg/g, Pb = 20.10~37.42 µg/g; the average concentration: As = 6.466 ± 3.077 µg/g, Pb = 28.88 ± 5.077 µg/g. By analysis vertically, the average concentration of As was 5.166 ± 1.496 µg/g in the upstream, 5.815 ± 1.793 µg/g in the midstream, and 9.716 ± 4.977 µg/g in the downstream. The average concentration of Pb was 27.83 ± 4.552 µg/g in the upstream, 28.66 ± 6.333 µg/g in the midstream, and 30.99 ± 4.837 µg/g in the downstream. It indicated that the concentration of As and Pb increased gradually from upstream to downstream. As existed mainly as insoluble state and Pb existed mainly as sulfide and organic combining state in surficial sediments, and the species of As and Pb could transform with the change of the circumstance. The release of quantity of As was higher than Pb. The pH of 6 was not conducive to the release of As and Pb. When the temperature was 35 and 6 °C, the release of As and Pb in surficial sediments were restrained, respectively. Fumaric acid and citric acid played an important role in promoting the release of As, but not conducive to Pb. Furthermore, the reasonable aeration rate was beneficial to the release process of As and Pb in surficial sediment. By kinetic analysis, the Elovich equation (Ct = 84.931-8.952lnt) could be used to describe the dynamic process of the release of As in a relatively short time. The Elovich equation (C t  = 2.724 + 1.3724lnt) and double constant rate equation (lnC T  = 1.4646 + 0.1522lnT) could well describe the dynamics process of the release of Pb.

Preparation, characterization, and phosphate removal and recovery of magnetic MnFe2O4 nano-particles as adsorbents.

Phosphate removal is an important method for controlling eutrophication in bodies of water. Adsorption is an effective phosphate removal approach. In this research, the adsorbent, namely, MnFe2O4, was prepared through the improved co-precipitation method and investigated in terms of phosphate removal. MnFe2O4 was characterized by scanning electron microscopy, vibrating sample magnetometry, X-ray diffraction, and Fourier transform infrared spectroscopy. Phosphate adsorption by MnFe2O4, desorption of adsorbed MnFe2O4 with the regeneration of desorbed MnFe2O4, and phosphate recovery were researched. Experimental results showed that adding the appropriate amount of polyethylene glycol to MnFe2O4 precursors during preparation inhibited the agglomeration of MnFe2O4 between particles because of the magnetic property of MnFe2O4 etc. High crystallinity and strong magnetism were achieved by MnFe2O4 at low temperatures. Average particle size was 5.1 nm. The hysteresis loops confirmed the ferrimagnetic behaviour of MnFe2O4 with a high saturation magnetization (i.e. 26.27 emu/g). The adsorption mechanism of phosphate was mainly physical. The prepared MnFe2O4 had a spinel structure. The proposed technique achieved a phosphate removal rate of 96.06%. A considerable amount of phosphate was desorbed from the adsorbed MnFe2O4 in 15 w/v% NaOH solution. The adsorption capacity of the desorbed MnFe2O4 could be restored to 96.73% in 10 w/v% NaNO3 solution through ion exchange. A sustainable phosphate source was recovered via hydroxyapatite crystallization in the desorption solution, which contained an abundant amount of phosphate as seed for suitable recovery condition. This finding suggested that MnFe2O4 could be a promising adsorbent for efficient phosphate removal.

[Magnetic resonance imaging of ovarian carcinosarcoma: correlation to the clinicopathological findings].

OBJECTIVE: To investigate magnetic resonance imaging (MRI) characteristics of ovarian carcinosarcoma and the diagnostic value of MRI. METHODS: The MRI features of ovarian carcinosarcoma and clinical data of 5 patients with ovarian carcinosarcoma were reviewed. All the lesions were confirmed by surgery and pathological examination. RESULTS: MRI of ovarian carcinosarcoma in the 5 cases all showed large tumor mass and heterogeneous high-intensity on T2-weighted images and low-intensity on T1-weighted images, with laminar or stripe-like enhancement. Hemorrhage and necrosis were also displayed in some lesions. In two cases, the tumors invaded the greater omentum, sigmoid colon and the body of the uterus, with regional lymph node involvement. Pelvic effusion was observed in all the cases with pelvic hematocele in 1 case. CONCLUSION: MRI is useful in the detection and staging of ovarian carcinosarcoma.