Enantioselective, Copper-Catalyzed Addition of Nucleophilic Silicon to Alkenyl-Substituted Phosphine Oxides

An enantioselective β-silylation of α,β-unsaturated phosphine oxide derivatives using a silylboronic ester as the silicon pronucleophile is reported. The reaction is catalyzed by copper salts in the presence of chiral pyridine–oxazoline (PyOx) ligands. Good to high enantioselectivities (≤ 95% ee) are obtained for β-aryl-substituted acceptors whereas alkyl residues in the β-position lead to a lower ee value for 1° and no reaction for 2° and 3°. The new method represents another way of accessing α-chiral silanes and complements the known β-borylation.

Wood Moisture-Content Measurement Accuracy of Impregnated and Nonimpregnated Wood

The influence of the impregnation process of pine wood (Pinus sylvestris L.) samples on the electrical resistance changes and the moisture-content measurement accuracy is presented in this paper. In this study, the resistances of impregnated and nonimpregnated green pine timber harvested from northern Poland were compared. An impregnation method based on a vacuum-pressure chamber was used. Copper salts were applied as the impregnated solutions. The obtained results of the electrical resistance comparison showed a dependence of wood resistance on the moisture content. Higher conductivity occurred in impregnated wood samples filled with copper salt compared with wood samples without impregnation. Noticeable differences in the electrical resistance values were observed when the wood moisture content was significantly above the Fibre Saturation Point (FSP).

Copper-catalyzed ultrasonic-promoted coupling of acetylene analogs, dialkyl azo dicarboxylate, and benzazoles to assemble tricyclic fused-ring [1,2,3]triazolo[3,4-b][1,3]benzazole analogs

: An unprecedented copper-catalyzed reaction of acetylene analogs with dialkyl azo dicarboxylate and benzazole analogs via a cross-coupling sequence was reported. A library of triazolobenzazole fused ring systems including [1,2,3]triazolo[3,4-b][1,3]benzothiazole, [1,2,3]triazolo[3,4-b][1,3]benzoxazole and [1,2,3]triazolo[3,4-b][1,3]benzimidazole structures were obtained in moderate to excellent yields under very mild reaction conditions. Structural confirmation of the final products became possible using different methods like spectroscopy and elemental analysis. The control experiments indicated C-H activation of acetylene by copper salts, followed by cycloaddition between a 2-(phenylethynyl)benzo[d]azol-3(2H)-yl anion and azo dicarboxylate as the key mechanistic feature. The broad substrate scope with simple and easily-affordable starting materials as well as mild reaction conditions are the noticeable attributes of this methodology which provides facile access to the desired products.

Towards chemotherapy of tuberculosis: experiments with external use of copper salts in lupus

The question of the treatment of various chronic diseases, especially tuberculosis, with drugs with chemotherapeutic properties, has long been in the focus of attention of researchers. Chemotherapy seeks mainly to influence the body with certain medicinal substances, which, while destroying _ pathogens, do not harm the body itself.

Optimization of Copper Stain Removal from Marble through the Formation of Cu(II) Complexes in Agar Gels

Copper complexes with different ligands (ethylenediaminetetraacetic acid, EDTA, ammonium citrate tribasic, TAC, and alanine, ALA) were studied in aqueous solutions and hydrogels with the aim of setting the optimal conditions for copper stain removal from marble by agar gels, with damage minimization. The stoichiometry and stability of copper complexes were monitored by ultraviolet-visible (UV-Vis) spectroscopy and the symmetry of Cu(II) centers in the different gel formulations was studied by electron paramagnetic resonance (EPR) spectroscopy. Cleaning effectiveness in optimized conditions was verified on marble laboratory specimens through color variations and by determining copper on gels by inductively coupled plasma-mass spectrometry (ICP-MS). Two copper complexes with TAC were identified, one having the known stoichiometry 1:1, and the other 1:2, Cu(TAC)2, never observed before. The stability of all the complexes at different pH was observed to increase with pH. At pH 10.0, the gel’s effectiveness in removing copper salts from marble was the highest in the presence of ALA, followed by EDTA, TAC, and pure agar gel. Limited damage to the marble surface was observed when gels with added EDTA and TAC were employed, whereas agar gel with ALA was determined to be the most efficient and safe cleaning material.

Surface Texturing Behavior of Nano-copper Particles under Various Copper Salts System during Copper-assisted Chemical Etching

In this work, the effects of different copper salts on the etching behavior of n-type monocrystalline silicon wafers were detailedly studied by Cu-assisted chemical etching method. Firstly, the inverted pyramid, inverted pyramid-like and oval pit texturing structures were obtained by HF/H2O2/Cu(NO3)2, HF/H2O2/CuSO4 and HF/H2O2/CuCl2 etching systems. Then, the evolution of copper particles deposition behavior was studied to reveal the influencing mechanism of different anion species, the textured wafer surfaces were characterized by scanning electron microscopy (SEM) and ultraviolet-visible (UV) spectrophotometer, the etching rate, silicon wafer thinning and the deposition amount of copper particle was systematically analyzed. We conclude that the binding force between anion and cation, the oxidation of anions and the formation of complex groups [CuCl2]− lead to great difference in the deposition behavior of copper, resulting in different etching morphology and etching rate. The moderate size copper particles deposited from HF/H2O2/Cu(NO3)2 system make that the etching process is mild and the anisotropic etching ability can fully demonstrated, and the regular inverted pyramid structures can be formed under low thinning of silicon wafers. This work will provide guidance for controllable preparation of inverted pyramid structure and future application in high efficiency solar cells.