Palladium Supported on Zinc Oxide Nanoparticles as Efficient Heterogeneous Catalyst for SuzukiMiyaura and Hiyama Reactions under Normal Laboratory Conditions

Nanoscale Pd supported on ZnO was prepared by a facile coprecipitation method. Pd/ZnO Nanoparticles were characterized by using XRD, TEM, SEM, XPS, BET specific surface area measurement, and thermogravimetric analysis. This catalyst was used as novel and excellent heterogeneous catalyst for ligand‐free C? C bond‐formation particularly in the synthesis of unsymmetrical biaryls by Suzuki? Miyaura and Hiyama cross‐coupling reactions under air atmosphere without use of any Ar or N₂ flow. The catalyst can be recovered and recycled several times without marked loss of activity.     

Microdetermination of collagenase and collagen

A method for the microdetermination of bacterial collagenase activity and different types of collagen is described. The assay can be used in the range of 2–60 μg for type I and from 10 to 60 μg for other types. Interference of other proteins was eliminated, even those that binds the Sirius red dye. The method is sensitive, rapid, and inexpensive in determination of collagen type I in its pure and fibril form and bacterial collagenase activity and its kinetic parameter.     

Cs6[TeMo6O24] · 2 Te(OH)6 · 4 H2O ? eine Tellursäure-reiche Einschlußverbindung

Cs₆[TeMo₆O₂₄] · 2 Te(OH)₆ · 4 H₂O – A Telluric Acid-rich Inclusion Compound Single crystals of Cs₆[TeMo₆O₂₄] · 2 Te(OH)₆ · 4 H₂O have been grown from aqueous solution. It crystallizes triclinically in space group P1 with Z = 1, a = 1 086.6(1), b = 1 095.6(1), c = 1 105.5(1) pm, α = 118.83(1), β = 106.22(1) and γ = 100.00(1)°. X-ray structure determination (5 755 reflections, 251 parameters, R_g = 0.0355) revealed an infinite chain consisting of hydrogen bonded (OH …? O 259.4(5) – 267.4(6) pm) Te(OH)₆ molecules and [TeMo₆O₂₄]^6? anions to be the Prominent structural feature. Further hydrogen bonds between neighbouring Te(OH)₆ molecules connect these chains to yield a two-dimensionally infinite arrangement.     

Synthesis,Characterization and Applications of Immobilized Iminodiacetic Acid-Modified Silica

Porous immobilized iminodiacetic acid modified silica of the general formula S—(CH₂)₃—N(CH₂COOH)₂, (where S represents [Si—O] _n siloxane network) has been prepared by replacement of the iodide in 3-iodopropyl modified silica with diethyliminodiacetate. The immobilized-diethyliminodiacetate ligand system (S-DIDA) was then hydrolyzed by hydrochloric acid to produce the immobilized iminodiacetic acid ligand system (S-IDA). The iodo functionalized modified silica (S-I) was prepared by polycondensation of Si(OEt)₄ and (MeO)₃Si(CH₂)₃I. The XPS and CP/MAS ¹³C NMR spectra showed that not all iodine atoms are replaced and that the hydrolysis of ethyl acetate groups are incomplete upon treatment with HCl. The immobilized iminodiacetic acid ligand system exhibits high potential for the uptake of various di- and trivalent metal ions such as (Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺). Complexation of the iminodiacetate ligand system for the metal ions at the optimum conditions was found in the order: Cu²⁺ > Fe³⁺ > Ni²⁺ > Co²⁺ > Mn²⁺ > Zn²⁺. Stability studies of the iminodiacetate ligand system showed that a degradation of the siloxane network and leaching of some species occurred upon treatment with strong acid and base aqueous solutions.     

Zinc oxide (ZnO) as a new, highly efficient, and reusable catalyst for acylation of alcohols, phenols and amines under solvent free conditions

Zinc oxide (ZnO) is a highly efficient catalyst for the acylation of a variety of alcohols, phenols and amines with acid chlorides or acid anhydrides under solvent free conditions. Primary, secondary, tertiary, allylic and benzylic alcohols, diols and phenols with electron donating or withdrawing substituents can be easily acylated in good to excellent yield.     

Nonaqueous oxidation of phosphites to phosphates in nucleotide synthesis

$\text{m}$-Chloroperbenzoic acid in methylene chloride represents a rapid non-aqueous method for the conversion of phosphites to phosphates during oligonucleotide synthesis both in solution and on a solid support.     

Experimental charge density of octafluoro-1,2-dimethylenecyclobutane: atomic volumes and charges in a perfluorinated hydrocarbon

Octafluoro-1,2-dimethylenecyclobutane, mp. 238 K, was crystallized in situ on a SMART 1000-CCD diffractometer, and high order X-ray diffraction data were collected at 100 K for a charge density determination. A topological analysis was applied and a partitioning of the molecule into atomic regions making use of Bader's zero flux surfaces yielded atomic volumes and charges. Corresponding atomic properties were also derived theoretically from B3LYP/6-311++G(3df,3pd) wavefunctions. While for carbon the volumes and charges are largely dependent on their bonding environment, fluorine has an almost constant atomic volume around 16-17 A3 and a charge between -0.6 and -0.7e, not only in the title compound, but also in two further perfluorinated hydrocarbons, of which the charge densities were determined earlier.     

Solvent-free Knoevenagel Condensations over TiO2

A study involving the scope of substrates in the Knoevenagel reaction under SFC has been conducted. Reactivity trends favored formation of the condensation product using both electron deficient and rich aryl aldehydes. A recycling study confirmed that the reaction medium could be used multiple times affording, with each run, the desired condensation product in excess of 95% conversion.     

LIGHT-DRIVEN H2 PRODUCTION WITH PROFLAVIN AND HYDROGENASE: COMPARISON OF CYTOCHROME C3 AND METHYL VIOLOGEN AS e- MEDIATORS

We have studied the hydrogenase-catalyzed production of H, when either its natural electron mediator cytochrome c₃ (c₃) or the artificial mediator methyl viologen (MV) was reduced by illumination of proflavin (PF) in the presence of ethylenediaminetetraacetate (EDTA). The reduction rates of MV and c₃ were comparable at equivalent concentrations of PF, taking into account the four redox sites of c₃. However, when the concentration of c₃ exceeded that of PF, the reduction rate decreased. We explain this by light quenching. In the H₂-producing system, MV was more efficient than c₃ as electron mediator when the initial reaction rates were compared. However, under certain conditions with MV, the rate of H₂ production decreased rapidly with time of illumination, whereas with c₃ it consistently remained stable. Possible reasons for this difference are discussed.
Severe inactivation of hydrogenase was observed in the absence of the primary electron donor EDTA. It is concluded that this inactivation is caused by the excited state of PF