Temporary Intramolecular Generation of Pyridine Carbenes in Metal‐Free Three‐Component C?H Bond Functionalisation/Aryl‐Transfer Reactions

Nucleophilic addition of pyridines to benzyne generates zwitterionic adducts that evolve by a rapid intramolecular proton shift to produce the corresponding pyridine carbenes, N‐phenyl pyrid‐2‐ylidenes. In the presence of electrophilic ketones (isatin derivatives), the pyridylidenes can further react by an original bis‐arylation reaction of the carbonyl compounds involving a formal pyridine C? H bond functionalisation. The overall transformation is an unprecedented three‐component reaction featuring a carbene intermediate. The mechanism of this transformation was examined in detail by using both experimental and theoretical approaches. It was found that the generation of N‐phenyl pyrid‐2‐ylidene from pyridine and benzyne is energetically favoured, and that the corresponding carbene dimer can also form easily. Under the three‐component reaction conditions, the pyridylidene preferentially adds to the ketone group of the isatin derivative to produce a zwitterionic adduct amenable to an intramolecular aryl transfer reaction by a concerted nucleophilic aromatic substitution. This peculiar reactivity for a carbene was compared to possibly competitive known reactions of stable carbenes with carbonyl compounds, and the reaction was found to be under thermodynamic control. The reported method of generation of N‐phenyl pyrid‐2‐ylidenes and their reactivity with carbonyl compounds unlock new perspectives in organic synthesis.     

Stability-Indicating UPLC Method for the Determination of Bisoprolol Fumarate and Hydrochlorothiazide: Application to Dosage Forms and Biological Sample

A sensitive, selective and accurate ultra performance liquid chromatographic method has been developed and validated for the simultaneous determination of bisoprolol fumarate and hydrochlorothiazide in their combined dosage forms and as well as in spiked human urine samples. The separation was achieved on an Acquity UPLC BEH C18 1.7 μm (2.1 × 50 mm) column, at 40 °C with mobile phase consisting of acetonitrile:phosphate buffer (20 mM) at pH 3.0 with a gradient elution at 225 nm. Bisoprolol fumarate and hydrochlorothiazide were well separated in <1.5 min with good resolution and without any tailing and interference of excipients. The method was fully validated according to ICH guidelines in terms of accuracy, precision, linearity and specificity. A linear response was observed over the concentration range 0.5–150 μg mL^?1 for hydrochlorothiazide and 0.5–250 μg mL^?1 for bisoprolol fumarate. Limit of detection and limit of quantitation for hydrochlorothiazide were calculated as 0.01 and 0.03 μg mL^?1, respectively, and for bisoprolol fumarate were 0.07 and 0.21 μg mL^?1, respectively. Moreover, bisoprolol fumarate and hydrochlorothiazide were subjected to degradation conditions such as hydrolytic, oxidative and thermal stress conditions to evaluate the ability of the proposed method for the separation of bisoprolol fumarate and hydrochlorothiazide from their degradation compounds.     

Iron Cyclopentadienone Complexes: Discovery,Properties, and Catalytic Reactivity

Iron cyclopentadienone complexes have recently received particular attention in organic chemistry. This is due to their easy synthesis from simple and cheap materials, air–water stability, and most importantly for their unique catalytic features arising from the presence of a non‐innocent ligand, triggering powerful redox properties. Herein we discuss the properties of such complexes from synthetic and mechanistic points of view, and their applications in original redox‐neutral transformations in both racemic and enantioselective series.     

Charge Polarization at a Au–TiC Interface and the Generation of Highly Active and Selective Catalysts for the Low‐Temperature Water–Gas Shift Reaction

Au atoms in contact with TiC(001) undergo significant charge polarization. Strong metal–support interactions make Au/TiC(001) an excellent catalyst for the low‐temperature water–gas shift (WGS), with turnover frequencies orders of magnitude larger than those observed for conventional metal/oxide catalysts. DFT calculations indicate that the WGS reaction follows an associative mechanism with HOCO as a key intermediate.     

Review of technetium chemistry research conducted at the University of Nevada Las Vegas

The chemistry of technetium is being explored at the University of Nevada Las Vegas. Our goal is to investigate both the applied and fundamental aspects of technetium chemistry, with a special emphasis on synthesis, separations, and materials science. The synthetic chemistry focuses on metal–metal multiple bonding, oxides and halides. Synthesis and characterizations of (n-Bu₄N)₂Tc₂X₈, Tc₂(O₂CCH3)₄X₂ (X = Cl, Br), TcO₂, Bi₂Tc₂O₇, Bi₃TcO₈, TcBr₃ and TcBr₄ have been performed. The applied chemistry is related to the behavior of Tc in the UREX process. Separation of U/Tc has been conducted using anion exchange resin and metallic Tc waste form synthesized and characterized.     

Neutrino masses in the supersymmetric SU(3)C⊗SU(3)L⊗U(1)X model with right-handed neutrinos

The R-symmetry formalism is applied for the supersymmetric SU(3)_C⊗SU(3)_L⊗U(1)_X (3-3-1) model with right-handed neutrinos. For this kind of models, we study the generalization of the MSSM relation among R-parity, spin and matter parity. Discrete symmetries for the proton stable in this model are imposed, and we show that in such a case it is able to give leptons masses at only the tree level contributions required. A simple mechanism for the mass generation of the neutrinos is explored. We show that at the low-energy effective theory, the neutrino spectrum contains three Dirac fermions, one massless and two degenerate in mass. At the energy level where the mixing among them with the neutralinos is turned on, neutrinos obtain Majorana masses and correct the low-energy effective result which naturally gives rise to an inverted hierarchy mass pattern. This mass spectrum can fit the current data with minor fine-tuning. Consistent values for masses of the charged leptons are also given. In this model, the MSSM neutralinos and charginos can be explicitly identified in terms of the new constraints on masses which is not as in a supersymmetric version of the minimal 3-3-1 model. PACS 11.30.Er; 14.60.Pq; 14.60.-z; 12.60.Jv     

Synthesis and characterization of amminecopper hexamolybdometalates

Representatives of a new class of heteropoly compounds (HPCs) have been synthesized. Such an HPC is an oligomer, which is built of two monomeric 6-heteropolyanions with the Perloff structure; these monomers are linked through an amminecopper cation. The composition of the new HPCs is Cu(NH₃)₄ · ?ub;H[MMo₆O₁₈(OH)₆] · 10H₂O?ub;₂Cu(NH₃)₄, where M = Al(III), Cr(III), Fe(III), Co(III), Ga(III), or Rh(III). The compounds have been characterized using IR spectroscopy, thermogravimetry, and X-ray powder diffraction.