Palladium approaches to beta- and gamma-carbolines

A variety of substituted beta- and gamma-carbolines containing aryl, alkyl, hydroxymethyl, ester and silyl functionality at the 3- and 4-positions have been prepared by the palladium-catalyzed iminoannulation of internal and terminal alkynes. This methodology has been successfully employed to the synthesis of two biologically active beta-carboline alkaloids, ZK93423 and abecarnil.;A variety of 3-substituted beta- and gamma-carbolines have been synthesized from N-substituted 3-iodo-1H-indole-2-carboxaldehydes and 2-bromo-1H-indole-3-carboxaldehydes, respectively. The coupling of these aldehydes with various terminal acetylenes using cat. PdCl 2(PPh3)2/CuI readily affords the corresponding alkynylindole carboxaldehydes, which have subsequently been converted to the corresponding tert-butylimines and cyclized to beta- and gamma-carbolines by either copper-catalyzed or thermal processes.;A variety of N-substituted 2-bromo-1H-indole-3-carboxaldehydes incorporating an alkyne-containing tether on the indole nitrogen have been converted to the corresponding tert-butylimines, which have been subjected to palladium-catalyzed intramolecular iminoannulation, affording various gamma-carboline derivatives with an additional ring fused across the 4- and 5-positions in good to excellent yields. This intramolecular concept has been extended to other palladium-catalyzed annulations to synthesize various complex heteropolycycles.;A novel 1,4-palladium migration has been observed by trapping the palladium intermediate generated from o-iodobiaryls by way of a Suzuki coupling reaction. The choice of reaction conditions is important in turning on and off the migration. There are important electronic effects controlling the distribution of the palladium intermediates, which is reflected in the isomer distribution of the Suzuki products

Preparation of MoS2 Microspheres with Different Proportions by Hydrothermal Method and their Gas Sensing Performance

MoS2 microspheres with three different proportions were prepared by hydrothermal method. The effects of different proportions on the morphology, purity and sensing performance of MoS2 were studied. The morphology and structure of MoS2 were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the MoS2 microspheres with the best morphology and the highest purity can be obtained when the ratio of Mo to S is 1:2. The results of gas sensitivity test show that the optimum working temperature of the three samples is 175℃. When the ratio of Mo to S is 1:2, the sensitivity to 100ppm-500ppm ethanol gas is obviously better than other ratios

Density Functional Theory Study on the Electrical Properties of α-CsPbX3 (X=I, Cl, Br)

All-inorganic perovskite solar cells have become more important in the commercialization of the photovoltaic devices. In this study the structural, electronic properties of inorganic metal halide cubic perovskites CsPbX3 (X = I, Br, Cl) for perovskite solar cells are simulated using first-principles Density Functional Theory (DFT). The newly adjusted parameters make the calculations more accurate. These compounds are semiconductors with direct band gap energy. Results suggest that the α-CsPbX3 (X=I, Cl, Br) have a wide bandgap adjustment range with potential application in solar cells and other optoelectronic energy devices. On the basis of the electronic properties, one can expect that the α-CsPbI3 would be a better used to perovskite solar cell. α -CsPbCl3 and α-CsPbBr3 better suitable for others photovoltaic device

The Photocatalytic Applications of TiO2-WO3 Heterostructure in Methylene Blue

In this work, TiO2-WO3 composite materials were forged by sol-gel method and the forged samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and UV-vis diffuse reflectance spectroscopy. The tough interaction in the interface of TiO2-WO3 heterostructures and the solar spectral response of TiO2 and WO3 reduce the electron-hole pair recombination rate and enhance the photoelectrochemical activity. The TiO2-WO3 heterostructures also show good adsorption ability for organic pollutants. This study testified that the fabricated TiO2-WO3 heterostructures are expectation materials for efficient water splitting as well as adsorption and photocatalytic wipe off organic pollutants

Structural, Electronic and Optical Properties of CsMI3(M=Ge,Sn,Pb) Perovskite from First Principles

The all-inorganic lead halide perovskites has received wide attention in optoelectronic applications such as solar cells and light-emitting diodes due to its high photoabsorption, suitable bandgap and good stability. Based on the first principles, the electronic structure and optical properties of the structure are studied by substituting all the lead elements in CsPbI3 with Ge and Sn.We found that the structural stability of all the substituted materials was enhanced. The tolerance factors of CsGeI3 and CsSnI3 were 0.934 and 0.874, respectively. The most important point is to replace the toxic Pb element, which not only reduces environmental pollution but also can be more suitable for commercial production. By analyzing the imaginary part of the dielectric function and absorption coefficient, it is found that the blue shift occurs in all the materials which replace Pb element, and the absorption ability of sun light is stronger in the visible light range, which proves the foundation for lead free perovskite solar cells

Synthesis of 1-substituted 3-amino-1H-1,2,4-triazoles from ethyl N-(5-phenyl-1,2,4-oxadiazol-3-yl)formimidate

A general and efficient method for the synthesis of 1-substituted 3-amino-1H-1,2,4-triazoles has been developed. The desired 3-amino-1H-1,2,4-triazoles (3) were prepared in good to excellent yields from ethyl N-(5-phenyl-1,2,4-oxadiazol-3-yl)formimidate (1a) and anilines or amines (2) via a one-pot process involving formimidamide formation followed by a thermal monocyclic rearrangement. The benzoyl protecting group could be readily removed by sulfuric acid promoted deprotection