Low-temperature interface modification by hydrocarbon radicals in heteroepitaxy of 3C-SiC on Si clean surface

An interface modification by hydrocarbon radicals from cracked-propane (C₃H₈) and dimethylgermane ((CH₃)₂GeH₂:DMGe) in heteroepitaxy of 3C-SiC on Si has been studied with in situ reflection high-energy electron diffraction (RHEED) and a high-resolution scanning electron microscope. In the case of cracked-C₃H₈, a clean Si surface is carbonized at 750°C. Whereas, in the case of DMGe, it can be carbonized reproducibly at as low as 650°C. A RHEED pattern of a carbonized layer prepared using DMGe indicates single-crystalline 3C-SiC without twins and Ge-related patterns. The activation energy in the range of 46.9-51.1 kcal/ mol is obtained in the initial stage of 3C-SiC growth for both hydrocarbon sources. The difference in 3C-SiC growth by using different hydrocarbon sources is discussed in detail.     

Trinuclear coordinatively labile Cu(II) complex of 4,6-O-ethylidene-beta-D-glucopyranosylamine derived Schiff base ligand and its reactivity towards primary alcohols and amines

A novel neutral trinuclear Cu(II) complex of a Schiff base ligand derived from D-glucose has been synthesised and structurally characterised, which exhibits excellent alcohol binding affinity and activates the C-Cl bond of chloroform in the presence of primary amine.     

Cp*RuCl-catalyzed [2 + 2 + 2] cycloadditions of alpha,omega-diynes with electron-deficient carbon-heteroatom multiple bonds leading to heterocycles

In the presence of a catalytic amount of Cp*RuCl(cod), 1,6-diynes were allowed to react chemo- and regioselectively with electron-deficient nitriles and heterocumulenes at 60-90 degrees C to afford heterocyclic compounds. The mechanism of the ruthenium-catalyzed regioselective formations of bicyclic pyridines and pyridones were analyzed on the basis of density functional calculations. Cyclocotrimerizations of ethyl propiolate with ethyl cyanoformate or propyl isocyanate gave rise to two of the four possible pyridine or pyridone regioisomers.     

Domino coupling relay approach to polycyclic pyrrole-2-carboxylates

CuBr2-catalyzed three-component coupling of N-benzylallylamine, ethyl glyoxalate, and terminal alkynes afforded glycine-tethered 1,6-enynes, which were further transformed into polycyclic pyrrole-2-carboxylates via novel cycloisomerization/Diels-Alder cycloaddition/dehydrogenation sequence under iridium-catalyzed conditions.     

Iridium-catalyzed ring cleavage reaction of cyclobutanone O-benzoyloximes providing nitriles

[reaction: see text] Iridium-catalyzed ring cleavage reaction of cyclobutanone O-benzoyloximes in the presence of 9,10-dihydroanthracene and potassium carbonate proceeds to give saturated nitriles via C-C bond fission at the sterically more hindered site.     

Temperature and energy dependence of the minimum yield in axial channeling

An analytical expression for the minimum yield in axial channeling is obtained using Lindhard theory for the real situation. The temperature and energy dependence agree well with a Monte-Carlo calculation by Barrett.     

Phase behavior and phase-transfer catalysis of tetrabutylammonium salts. Interface-mediated catalysis

The phase behavior and component composition of the coexisting phases in the tetrabutylammonium bromide (TBABr)/benzene/water/NaBr four-component system were strongly influenced by the temperature, TBABr content, and NaBr concentration. The phase-transfer catalytic activity of TBABr for the reaction of decyl methanesulfonate with sodium bromide was closely related to the phase behavior. Under O (oil-rich phase) + L (TBABr-rich liquid phase) + W (aqueous phase) triphase conditions, the influences of temperature and stirring speed on the phase-transfer catalytic activity were small compared with those under O + W biphase conditions. The addition of other quaternary salts that were able to form w/o aggregates in the O phase enhanced the TBABr catalytic activity even under O + W conditions. The relationship between phase behavior and catalytic activity of tetrabutylammonium chloride or iodide (TBACl or TBAI) was also examined. The results strongly suggested that the catalysis of TBAX was attributable to the interfacial reactions of TBAX with the substrate. The interface includes the water-oil microinterface formed in the microemulsion-like L phase as well as the bulk water-oil interface.