Synthesis of nickel(II)-di(2,3-dichlorophenyl)carbazonate and its adduct formation with heterocyclic nitrogen bases

The nickel(II)-di(2,3-dichlorophenyl)carbazonate [Ni(D2,3DClPC)₂] complex has been prepared and characterized by elemental and spectral studies. The Ni^II chelate forms adducts with heterocyclic nitrogen bases, which were studied spectrophotometrically in monophase CHCl₃ media. Saturated monodentate bases such as pyrrolidine, piperidine, etc., form pentacoordinate adducts of 1:1 stoichiometry, whereas bidentate and unsaturated monodentate bases form hexacoordinated adducts with 1:1 and 1:2 metal–ligand stoichiometries respectively. The results are discussed interms of steric properties, basicity and ring structures of the heterocyclic bases.     

Direct Asymmetric Hydrogenation and Dynamic Kinetic Resolution of Aryl Ketones Catalyzed by an Iridium-NHC Exhibiting High Enantio- and Diastereoselectivity

A chiral iridium carbene-oxazoline catalyst is reported that is able to directly and efficiently hydrogenate a wide variety of ketones in excellent yields and good enantioselectivity (up to 93 % ee). Moreover, when using racemic α-substituted ketones, excellent diastereoselectivities were obtained (dr 99:1) by dynamic kinetic resolution of the in situ formed enolate. Overall, the herein described hydrogenation occurs under ambient conditions using low hydrogen pressures, providing a direct and atom efficient method towards chiral secondary alcohols.     

Ethanol as a Hydrogenating Agent: Palladium-Catalyzed Stereoselective Hydrogenation of Ynamides To Give Enamides

Ethanol is shown to act as a hydrogenating agent for ynamides under palladium catalysis. This behavior is different from the normally expected reaction of ethanol addition to alkynes. The reaction shows stereoselectivity for E enamides, which is in contrast to reports using other hydrogenating sources. The method was also extended to ynamines. Alternatively, the use of ethanol and ammonium formate as the hydrogenating source gives Z enamides. The role of ethanol in hydrogenation was demonstrated by means deuterium labeling experiment.     

Organo-Oxotin Cages Containing Arsinate Ligands

Abstract

New monoorgano-oxotin cages which possess bridging arsinate ligands have been prepared and characterized by X-ray and ¹¹⁹Sn NMR spectroscopy. The tetrameric, trimeric, and dimeric tin compounds containing arsinate ligands and six-and four-membered stannoxane rings exhibit characteristics which parallel the phosphinate-bridged cages previously reported.^1,2 Conversion of the tetrameric cube structure, [n-BuSnO(O₂AsMe₂)]₄, to a mixed butterfly composition is easily accomplished by addition of arsinic, phosphinic, or carboxylic acid. For example, two butterfly compounds that we formed are: [n-BuSn(OH)(O₂AsMe₂)(OP(O)Me₂)]₂ and [n-BuSn(OH)(0₂AsMe₂)(OAs(O)Me₂)]₂.     

Thermoresponsive N-vinyl caprolactam grafted sodium alginate hydrogel beads for the controlled release of an anticancer drug

A series of thermoresponsive sodium alginate-g-poly(vinyl caprolactam) (NaAlg-g-PNVCL) beads were prepared as drug delivery matrices of 5-flurouracil (5-FU) crosslinked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Graft copolymers of sodium alginate with vinyl caprolactam were synthesized using azobisisobutyronitrile as an initiator, and characterized by Fourier infrared spectroscopy, differential scanning calrimetry and X-ray diffraction for analysis of the amorphous nature drug in the beads, and by scanning electron microscopy for the spherical nature of the beads. Preparation condition of the beads was optimized by considering the percentage of encapsulation efficiency, swelling behavior of beads and their release data. Effects of variables such as GA concentration, drug/polymer ratio and catalyst concentration on the release of 5-FU were carried out at two different temperatures (25 and 37 °C) in simulated intestinal fluid for 12 h. It was observed that, drug release from the beads decreased with increasing drug/polymer (d/p) ratio, extent of crosslinking agent and catalyst concentration. The swelling degree of graft copolymer beads was found to be increased with decreasing of environmental temperature. In vitro release studies were performed at 25 and 37 °C for 12 h, and showed that thermoresponsive graft copolymer beads had higher drug release behavior at 25 °C than that at 37 °C, following Fickian diffusion transport mechanism with slight deviation.     

Molecular and crystal structures of bis-tetrazolate ammonium salt and bis-tetrazole monohydrate

The title compounds bis-tetrazolate ammonium salt (I) and bis-tetrazole monohydrate (II) are synthesized and studied by single crystal and powder X-ray diffraction, IR and elemental analyses. Compound I crystallizes in the monoclinic space group C2/m, a = 8.8862(17) Å, b = 11.2334(21) Å, c = 3.7269(7) Å, β = 99.4(6)°, V = 367.03 ų (12), Z = 2. Compound II crystallizes in the monoclinic space group P2₁/c, a = 5.1701(9) Å, b = 4.7506(8) Å, c = 15.2197(24) Å, β = 107.2(7)°, V = 357.09(10) ų, Z = 2. In the structure of I, both ammonium cation and bis-tetrazolate counter-anion are located on twofold crystallographic axes, moreover, the bis-tetrazolate anion has a mirror plane passing through the ’C1-C1a bond. In the crystal structure of (II), the bis-tetrazole molecule sits on the twofold axis (bisecting the C1-C1a bond), whereas the solvent water molecule occupies a general position. In the crystal structure of (I), the molecules are packed via N-H…N intermolecular interactions. In the crystal structure of (II), the molecules are packed via N-H…O and O-H…O intermolecular interactions. In addition, the crystal packing of both structures is further strengthened by π-π stacking interactions.     

Decomposition of 2-propanol on an intermetallic compound for hydrogen storage

Decompositon of 2-propanol has been carried out on the hydrogen storage material Mg₂Cu and its modified form (OH–Mg₂Cu) to study their catalytic behavior. The reaction was carried out in a continuous flow type reactor in the temperature range of 403–513 K at various flow rates. Mg₂Cu showed good catalytic activity with large amounts of condensation products. Its modified form gave acetone as the only products. The reason for these differences is explained in terms of differences in the structure of the catalyst as determined by XRD and XPS, as well as by surface area measurements. The reason for the formation of condensation products is discussed.     

A translation plane of order 72 with a very small translation complement

A translation plane of order 7² is constructed whose left nucleus is a cyclic group of order 6. Generally the translation complement of a translation plane is quite large when compared to the order of the left nucleus. The plane discussed in this paper has the distinguished feature that its translation complement modulo the scalar collineations group is very small. In fact it is a Dihedral group of order 12 and is the smallest of all the known examples. The translation complement divides the set of ideal points into 9 orbits of lengths 1,1, 6, 6, 6, 6, 6, 6, and 12.