Efficient construction of C–C bonds from aryl halides/aryl esters with arylboronic acids catalysed by palladium(II) thiourea complexes

A new set of palladium(II) complexes comprising phenyl(thiazolyl)thiourea ligands have been successfully synthesized and characterized with the aid of analytical as well as spectral (IR, UV–visible and NMR) methods. A distorted square‐planar geometry with N^S coordination mode of thiourea ligands in the new palladium complexes was corroborated by single‐crystal X‐ray diffraction methods. Interestingly, the palladium(II) thiourea complexes showed the highest catalytic activity with 0.1 mol% catalyst loading in Suzuki–Miyaura cross‐coupling reactions utilizing a range of aryl bromides/unactivated aryl chlorides with arylboronic acids as coupling partners in aqueous–organic media. Syntheses of diaryl ketones using aryl esters and arylboronic acids as coupling partners were also achieved with low catalyst loading within 20 h. The potential of our catalyst was demonstrated by its wide substrate scope, low catalyst loadings and high isolated yield. Moreover, the influences of key parameters like solvent, base, temperature and catalyst loading were also investigated.     

Synthesis of bis-α-amino acids through proline catalyzed asymmetric α-amination of higher homologs of Garner's aldehyde

A very convenient synthesis of bis-α-amino acids from the higher homologs of Garner's aldehyde is reported. The key step is proline catalyzed asymmetric amination of the aldehydes using dibenzylazodicarboxylate. The aldehydes used are either commercially available or can easily be prepared from aspartic or glutamic acid. One of the two chiral centers in the bis-amino acids comes from the aldehyde and the other one is generated through the proline catalyzed reaction, which were high yielding and proceeded with very high diastereoselectivity (93–99%). The reported route offers a general method for the synthesis of the title compounds with desired stereochemical outcome.     

Synthesis and Crystal Structure Analysis of 9-Phenyl-β-carboline

An efficient method is described for the synthesis of 9-phenyl-9H-pyrido[3,4-b]indole and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole by employing a catalytic amount of CuI (10 mole%) without any ligand. The single crystal of 9-phenyl-9H-pyrido[3,4-b]indole was produced by crystallization from hexane and ethyl acetate mixture that was investigated by single X-ray diffraction (XRD). The compound crystallizes in monoclinic P21/c space group with unit cell dimensions a = 11.3132(5) Å, b = 12.0061(5) Å, c = 9.2498(4) Å, α = 90°, β = 103.187(3)°, γ = 90°. ¹H and ¹³C NMR, IR, and mass spectroscopic methods of the compounds are also discussed.     

Optimisation of the analytical method for octa-, nona- and deca-brominated diphenyl ethers using gas chromatography–quadrupole mass spectrometry and isotope dilution

An analytical method for higher brominated congeners of polybrominated diphenyl ethers (PBDEs) was optimised using a gas chromatograph equipped with an electron impact ionisation-quadrupole mass spectrometer (GC-EI-qMS) and five native PBDEs and three ¹³C₁₂-labelled congeners in biological and environmental samples (mussels, sediment, dust). In the optimised instrumental conditions, abundance and repeatability improved with increase in temperature of the ion source. The instrumental detection limits (IDLs) for BDE-196, BDE-197, BDE-206, BDE-207 and BDE-209 were 0.1, 0.1, 0.2, 0.3 and 0.6?pg, respectively. When compared to the previous reports, the IDLs were the same as for electron capture negative ionisation (ECNI) or EI-double focusing magnetic sector (EI-Sector) mass spectrometer, indicating that sensitive determination could be achieved using a conventional GC-EI-qMS. Validation of the method was carried out by the analysis of reference materials and mussel samples. We confirmed that the concentrations quantified using this method was in the range of reported values for reference materials. Similar concentrations were found in mussels, which were analysed previously by our group. Thus, we conclude that a conventional GC-EI-qMS can be applied for analysis of higher brominated PBDEs in various environmental and biota matrices.     

Synthesis, characterization, and growth mechanism of α-Cr2O3 monodispersed particles

Monodispersed spherical particles of chromium (III) oxide, α-Cr₂O₃, were successfully synthesized from a diluted solution of KCr(SO₄)₂·12H₂O using the Aqueous Chemical Growth (ACG) technique. The spherical α-Cr₂O₃ particles obtained were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy for structural, surface morphological, chemical, and physical properties, as a function of deposition time. The XRD and Raman spectroscopy showed that aging had no apparent effect on the structure of the obtained uniform fine (in the range of micron-nano-level)-spherical particles of α-Cr₂O₃. The use of SEM demonstrated that aging had a clear influence on the size and the particles size distribution. Accordingly, the time dependence of the average diameter of α-Cr₂O₃ spherical particles follows the d³ law as required for diffusion-limited Ostwald ripening.     

Evaluation of Nanostructured coating layers formed on Ni balls during mechanical alloying of Cu powder

A novel coating method utilizing mechanical alloying was used to deposit a nickel-copper solid solution on the surface of nickel balls in a planetary ball mill. Mechanically milled copper powders were deposited by cold welding on the activated surface of the nickel balls. The impact of the nickel balls causes surface wear, leading to formation of mixed layered particles of copper-nickel and rewelding. In addition, diffusion takes place through the coating layer to form a Ni-Cu solid solution. The hardness of the coating reached a threefold increase (HV_0.01594) in comparison with the substrate hardness. Microstructural characterization of the coating surface performed using an optical microscope, SEM, and EPMA indicates that, with appropriate processing conditions, a thick, fully dense coating can be metallurgically bonded to the nickel balls. XRD results revealed the presence of a solid solution and nanocrystalline structure.     

Synthesis and Characterization of Rare Earth Orthovanadate (RVO4; R = La, Ce, Nd, Sm, Eu & Gd) Nanorods/Nanocrystals/Nanospindles by a Facile Sonochemical Method and Their Catalytic Properties

We report herein on an efficient sonochemical method for the synthesis of rare earth orthovanadate nanorods/nanoparticles/nanospindles, (general formula RVO₄; R = La, Ce, Nd, Sm, Eu and Gd). TGA, XRD, FTIR, Raman, UV–Vis, and TEM studies are employed for their characterization and for understanding their morphologies. In order to vary the textural properties of the rare earth vanadates, two surfactants, polyethylene glycol (PEG) and amphiphilic triblock copolymer Pluronic P123, are chosen in the preparation. While the sonochemical synthesis in the presence of PEG results in the formation of nearly spherical nanoparticles of LaVO₄, CeVO₄, SmVO₄ and EuVO₄, the same technique yields nanorods and nanospindles of NdVO₄ and GdVO₄, respectively. When P123 is used as the surfactant, the morphologies of RVO₄ are strikingly different, and in most cases nanorods and nanospindles are formed. The photocatalytic activities of the rare earth orthovanadate have been evaluated by studying the degradation of methylene blue, and CeVO₄ seems to be the best catalyst in the heterogeneous photolysis. The electrocatalytic activity of the vanadates has been examined by studying the hydrogen evolution reaction using a linear sweep voltammogram technique in 1 M of a H₂SO₄ solution. GdVO₄ seems to be the best electrocatalyst. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Lewis Acid Catalyzed Selective Reactions of Donor–Acceptor Cyclopropanes with 2‐Naphthols

Lewis acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with 2‐naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)₃ as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene‐fused cyclopentanes. Interestingly, engaging Sc(OTf)₃ as the Lewis acid, a Friedel–Crafts‐type addition of 2‐naphthols to cyclopropanes takes place, thus affording functionalized 2‐naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields.