EtOAc-dispersed magnetic nanoparticles (DMNPs) of γ-Fe2O3 in the single-pot domino preparation of 5-oxo-2-thioxo-3-thiophenecarboxylate derivatives

EtOAc-dispersed magnetic nanoparticles (DMNPs) of γ-Fe₂O₃ represent a straightforward and green catalyst for the rapid three-component synthesis of 5-oxo-2-thioxo-3-thiophenecarboxylate derivatives as rhodanine skeletons via a single-pot domino process. The rhodanines were prepared over magnetic nanoparticles of γ-Fe₂O₃ without any salt or additives. Dispersed nano-γ-Fe₂O₃ have many advantages, such as stability in air, reusability, reactions with high efficiency, simple separation with magnetic external field from mixture reactions, chemical stability, and also low toxicity.     

Mechanochemical synthesis of rutile-type CrMO4 (M=V, Sb) and their solid solutions

Grinding a mixture of hydrous amorphous chromium oxide (Cr₂O₃·nH₂O), vanadium oxide (V₂O₅) and antimony oxide (Sb₂O₅) was conducted by using a planetary ball mill, to investigate their mechanochemical reactions to form chromium vanadium oxide (CrVO₄) and chromium antimony oxide (CrSbO₄). The synthesis reactions proceed with an increase in grinding periods of time. The ground samples consist of agglomerates with particle size of about ten nanometers. The synthesized CrVO₄ sample exhibits a rutile-type tetragonal crystal structure, which is a high pressure phase. Additionally, solid solutions, CrV_1−xSb_xO₄ (x=0∼1, Δx=0.25), have been synthesized mechanochemically from the mixtures of Cr₂O₃·nH₂O, V₂O₅ and Sb₂O₅.     

Mild and efficient method for the cleavage of benzylidene acetals using HClO4-SiO2 and direct conversion of acetals to acetates

HClO₄-SiO₂ has been used successfully for the deprotection of benzylidene acetals and the direct conversion of benzylidene acetals to the corresponding di-O-acetates. The reactions are very fast and yields are excellent.     

Magnetic diphase nanostructure of ZnFe2O4/γ-Fe2O3

Magnetic diphase nanostructures of ZnFe₂O₄/γ-Fe₂O₃ were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic nanostructure of ZnFe₂O₄/γ-Fe₂O₃ was formed, in which the presence of ZnFe₂O₄ enhanced the thermal stability of γ-Fe₂O₃. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase α-Fe₂O₃. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with γ-Fe₂O₃ content.     

Hydrogenation of CO2 Promoted by Silicon-Activated H2S: Origin and Implications

Unlike the usual method of CO_x (x = 1, 2) hydrogenation using H₂ directly, H₂S and HSiSH (silicon-activated H₂S) were selected as alternative hydrogen sources in this study for the CO_x hydrogenation reactions. Our results suggest that it is kinetically infeasible for hydrogen in the form of H₂S to transfer to CO_x at low temperatures. However, when HSiSH is employed instead, the title reaction can be achieved. For this approach, the activation of CO₂ is initiated by its interaction with the HSiSH molecule, a reactive species with both a hydridic H^δ− and protonic H^δ+. These active hydrogens are responsible for the successive C-end and O-end activations of CO₂ and hence the final product (HCOOH). This finding represents a good example of an indirect hydrogen source used in CO₂ hydrogenation through reactivity tuned by silicon incorporation, and thus the underlying mechanism will be valuable for the design of similar reactions.     

Highly regio- and stereocontrolled brominations of gem-difluorinated vinyloxiranes

gem-Difluorinated vinyloxiranes, which are useful synthetic intermediates for difluorinated compounds, were brominated regio- and stereoselectively. Introduction of bromide at the allylic epoxide carbon with inversion of stereochemistry was realized by MgBr₂·Et₂O to furnish an anti vic-bromohydrine, whereas the reaction with LiBr/AcOH afforded the other diastereomer selectively. Moreover, both reactions at high temperature allowed to obtain, the thermodynamically favored products, E-allylic alcohols dominantly.     

Theoretical investigation on structures and isomerizations of the aluminum chlorogermylenoid H2GeClAlCl2

The aluminum chlorogermylenoid H₂GeClAlCl₂ was studied for the first time by using the DFT B3LYP and QCISD methods in gas phase and in C₆H₁₂, THF, DMSO, and H₂O solvents. The theoretical calculations predicted that H₂GeClAlCl₂ has three equilibrium configurations, in which the p-complex is the lowest in energy and is the most stable structure. The isomerization reactions among the three complexes have been investigated. The p-complex is suggested to be the predominant form of H₂GeClAlCl₂ in the gas phase and in solutions thermodynamically and kinetically.     

Highly efficient copper/palladium-catalyzed tandem Ullman reaction/arylation of azoles via C-H activation: synthesis of benzofuranyl and indolyl azoles from 2-(gem-dibromovinyl)phenols(anilines) with azoles

In this paper, a novel and highly efficient copper/palladium-catalyzed tandem intramolecular Ullman-type C-O(N) coupling reaction of 2-(gem-dibromovinyl)phenols(anilines) followed by an intermolecular arylation of azoles through C-H activation has been developed. In the presence of CuBr with Pd(PPh₃)₂Cl₂ used as co-catalyst, and LiO^tBu as a base, the one-pot reactions of 2-(gem-dibromovinyl)phenols and 2-(gem-dibromovinyl)anilines with a variety of azoles, including oxazoles, imidazoles, thiazoles, and oxadiazoles underwent smoothly in toluene at 100 °C to generate the corresponding biheteroaryl products in high yields. A tentative mechanism of copper/palladium-catalyzed tandem reaction was described.     

Structural originations of irreversible capacity loss from highly lithiated copper oxides

We use electrochemistry, high-energy X-ray diffraction (XRD) with pair-distribution function analysis (PDF), and density functional theory (DFT) to study the instabilities of Li₂CuO₂ at varying state of charge. Rietveld refinement of XRD patterns revealed phase evolution from pure Li₂CuO₂ body-centered orthorhombic (Immm) space group to multiphase compositions after cycling. The PDF showed CuO₄ square chains with varying packing during electrochemical cycling. Peaks in the G(r) at the Cu-O distance for delithiated, LiCuO₂, showed CuO₄ square chains with reduced ionic radius for Cu in the 3+ state. At full depth of discharge to 1.5 V, CuO was observed in fractions greater than the initial impurity level which strongly affects the reversibility of the lithiation reactions contributing to capacity loss. DFT calculations showed electron removal from Cu and O during delithiation of Li₂CuO₂.     

One-pot synthesis of α-aminophosphonates catalyzed by antimony trichloride adsorbed on alumina

SbCl₃ adsorbed on Al₂O₃ is found to be an efficient and recyclable catalyst in promoting three-component coupling reactions of aldehydes (aromatic and aliphatic), amines (aryl amines, aliphatic amines and esters of S-α-amino acids) and dialkylphosphites to afford the corresponding α-aminophosphonates in high yields. The ethyl ester of S-phenylalanine was observed to yield the corresponding α-aminophosphonate with S,S-diastereoisomer formed in dominance over the S,R-diastereoisomer.     

An efficient route to disymmetrically substituted calix[6]arenes. Synthesis of novel ligands presenting a N2S or N3CO2 binding core

The C_3v tris-methoxy calix[6]arene was selectively mono-alkylated by dibromoethane yielding a key intermediate for the design of disymmetrically O-substituted calix[6]arenes. Indeed, subsequent reactions with various functional groups afforded novel calix[6]arene-based biomimetic ligands that present a mixed donor N₂S or N₃CO₂⁻ environment in an efficient way.     

Synthesis of substituted imidazolines via [3+2]-cycloaddition of aziridines with nitriles

An efficient synthesis of 2,4-disubstituted 1H-imidazolines from aziridines and nitriles in the presence of BF₃-Et₂O or triethyloxonium tetrafluoroborate has been described. The reaction proceeds via a [3+2]-cycloaddition reaction. Most of the nitriles successfully underwent cycloaddition reactions with aziridines even at room temperature in a very short time.     

CO2 capture properties of M-C-O-H (M=Li, Na, K) systems: A combined density functional theory and lattice phonon dynamics study

We have computed the phase diagrams for multi-component M-C-O-H (M=Li, Na, K) systems using first-principles density functional theory complemented with lattice phonon calculations. We have identified all CO₂ capture reactions that lie on the Gibbs free energy convex hull as a function of temperature and the partial pressures of CO₂ and H₂O. Our predicted phase diagrams for CO₂ capture reactions are in qualitative and in some instances quantitative agreement with experimental data. The Na₂CO₃/NaHCO₃ and K₂CO₃/KHCO₃ systems were found to be the most promising candidates of all those we investigated for both pre- and post-combustion CO₂ capture. Overall, we show that our calculation approach can be used to screen promising materials for CO₂ capture under different conditions of temperature and pressure.     

Pentafluoro-λ-sulfanyl (SF5) perfluoroalkyl iodides-synthesis and reaction with ethylene and tetrafluoroethylene : Crystal structure of SF5(CF2)4CH2CH2I

A series of reactions between SF₅CF₂CF₂I and SF₅(CF₂)₄I with F₂CCF₂ was carried out in an effort to find the most effective methods for chain-extension. Also, for the first time, SF₅(CF₂)₈I and SF₅(CF₂)₁₀I have been prepared and isolated. The reaction conditions for the addition of H₂CCH₂ were also investigated. A determination of the crystal structure of the SF₅(CF₂)₄CH₂CH₂I has been carried out: the crystal system is monoclinic, with space group P2(1)/n and a=23.465(5) Å; b=6.0971(12) Å; c=44.892(9) Å; α=90°; β=99.38(3)°; γ=90°; Z=20.     

The solid state reaction between lanthanum oxide and strontium carbonate

The reaction between lanthanum oxide and strontium carbonate was studied non-isothermally between 350 and 1150 °C at different heating rates, intermediates and the final solid product were characterized by X-ray diffractometry (XRD). The reaction proceeds through formation of lanthanum oxycarbonate La₂O(CO₃)₂, lanthanum dioxycarbonate La₂O₂CO₃, and non-stoichiometric strontium lanthanum oxide La₂SrO_x (x = 4 + δ). La₄SrO₇ was found to be the final product which begins to form at ∼700 °C. Li⁺ doping enhances the formation of the final product as well as commencement of the reactions at lower temperatures.     

Synthesis, structural characterization and ferrimagnetic property of MnPS3 intercalated with nickel(II) cyclopolyamine complex cations

Two new intercalation compounds were prepared by the reactions of Ni(II) cyclopolyamine complex cations with a preintercalate Mn_1−xPS₃K_2x(H₂O)_y, respectively, through “ion exchange” process. Their structures were characterized by elemental analysis, X-ray powder diffraction and infrared spectroscopy. The lattice spacing increased 0.567 and 1.093 nm with respect to the pristine MnPS₃. Ferrimagnetism of the intercalates was confirmed by SQUID experiment with T_c at 40 and 33 K, respectively.     

Synthesis of 5-substituted 2-(4- or 3-methoxyphenyl)-4(1H)-quinolones

5-Substituted 7-methoxy-2-(4- or 3-methoxyphenyl)-4(1H)-quinolones 8-17 have been synthesised in good yields from the corresponding 7-methoxy-2-(4- or 3-methoxyphenyl)-5-trifluoromethanesulfonate-4(1H)-quinolones 7 via palladium-mediated cross-coupling reactions or aromatic nucleophilic substitution (SN_Ar) reactions.     

Copper(II) triflate promoted cycloaddition of α-alkyl or aryl substituted N-tosylaziridines with nitriles: a highly efficient synthesis of substituted imidazolines

Cu(OTf)₂ or Zn(OTf)₂ mediated [3+2] cycloaddition reactions of various α-alkyl or aryl substituted N-tosylaziridines with nitriles is described for the syntheses of substituted imidazolines. A mechanism for the cycloaddition is proposed to rationalize the formation of a nonracemic imidazoline from optically pure aziridine.     

Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2

A new V(III) lithium phosphate Li₅VO(PO₄)₂ has been synthesized by electrochemical insertion of lithium into Li₄VO(PO₄)₂. This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li₄VO(PO₄)₂ and to the tunnel structure of VO(H₂PO₄)₂. The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H₂PO₄)₂ and going to the final phase Li₅VO(PO₄)₂ are explained on the basis of the flexible coordinations of V⁴⁺ and V³⁺ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality.     

Coordination compounds with XeF2, AsF3 and HF as ligands to metal ions: a review of reaction systematics, Raman spectra and metal, fluoro-ligand polyhedra

The reactions between Ln(AsF₆)₃ (Ln: lanthanide) and excess of XeF₂ in anhydrous HF (aHF) as a solvent yield coordination compounds [Ln(XeF₂)₃](AsF₆)₃ or LnF₃ together with Xe₂F₃AsF₆ or mixtures of all mentioned products depending on the fluorobasicity of XeF₂ and LnF₃ along the series. XeF₂ in a basic aHF is able to oxidize Pr³⁺ to Pr⁴⁺ besides Ce³⁺ to Ce⁴⁺ and Tb³⁺ to Tb⁴⁺. The tetrafluorides obtained are weaker fluorobases as XeF₂ and are immediately exchanged with XeF₂ yielding Xe₂F₃AsF₆ and LnF₄. The analogous reaction between Ln(BiF₆)₃ and XeF₂ in aHF yields [Ln(XeF₂)₃](BiF₆)₃, Ln: La, Nd. Raman spectra of the compounds [Ln(XeF₂)_n](AF₆)₃ (A: As, Bi) show that no XeF⁺ salts are formed. The interaction of XeF₂ with metal ion is covalent over the fluorine bridge. Analogous reactions of Ln(AsF₆)₃ with AsF₃ in aHF yield [Ln(AsF₃)₃](AsF₆)₃ which are stable in a dynamic vacuum at temperatures lower than 233 K. In reactions between M(AF₆)₂ (M: alkaline earth metal and Pb, A: As, Sb) and XeF₂ in aHF as a solvent, compounds of the type [M(XeF₂)_n](AF₆)₂ were synthesized. Analogous reactions with AsF₃ yield coordination compounds of the type [M(AsF₃)_n](AsF₆)₂. During the preparation of M^x(AsF₆)_x (M: metal in oxidation state x+) by the reaction between metal fluoride and excess of AsF₅ in aHF it was found that HF could also act as a ligand to the metal ions (e.g. Ca(HF)(AsF₆)₂).