Direct C2-trifluoromethylation of indole derivatives catalyzed by copper acetate

Direct C2-selective trifluoromethylation of indole derivatives was achieved with Togni’s hypervalent iodine reagent and CuOAc as a catalyst in MeOH under mild conditions, affording the desired C2-trifluoromethylated indoles in good yield (up to 90%).     

Giant dielectric susceptibility and magnetocapacitance effect in manganites at room temperature

Extremely high values of the relative permittivity up to 10⁷ and the magnetocapacitance up to 10⁵% have been found in La_{1 − x} Sr _x MnO₃ single crystals (x = 0.1, 0.11). These phenomena are observed even at room temperature. The observed behavior can be a consequence of the strong interaction among charge, spin, and lattice degrees of freedom, which leads to charge and phase separation in the regime before the percolation threshold.     

Large enhancement of the thermoelectric Seebeck coefficient for amorphous oxide semiconductor superlattices with extremely thin conductive layers

Herein we demonstrate that amorphous oxide semiconductor (AOS) superlattices composed of a‐In–Zn–O (well) and a‐In–Ga–Zn–O (barrier) layers, fabricated on SiO₂ glass substrate by pulsed laser deposition at room temperature, exhibited an enhanced Seebeck coefficient |S |. The |S | value increases drastically with decreasing a‐In–Zn–O thickness (d_IZO) when d_IZO < ∼5 nm, and reached 73 µV K^–1 (d_IZO = 0.3 nm), which is ∼4 times larger than that of bulk |S |_3D (19 µV K^–1), while it kept its high electrical conductivity, clearly demonstrating that the quantum size effect can be utilized in AOS superlattices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Examination of surface adsorption of sodium chloride and sodium dodecyl sulfate by surface potential measurement at the air/solution interface

The surface potential (DeltaV) of the air/sodium chloride solution interface was measured by using an ionizing (241)Am electrode method at 298.2 K. The surface potential steeply increased from 0 up to 15 mV with increasing concentration, then gradually increased up to 20 mV between 1 and 10 mmol dm(-3), and finally stayed almost constant at 20 mV up to the concentration of 20 mmol dm(-3). This result means that sodium ions concentrate more just near the air/solution interface, whereas chloride ions concentrate more far below the interface above the bulk region of electroneutrality. The dipole moment was derived from the surface potential value, from which the width of the interfacial layer was estimated as a function of the magnitude of electric charge. As for the sodium dodecyl sulfate solution, on the other hand, the surface potential steeply decreased from 0 down to -80 mV with increasing concentration from 0 to 0.01 mmol dm(-3), then rapidly increased up to -50 mV between 0.1 and 3 mmol dm(-3), then linearly increased up to 0 mV with increasing concentration from 3 mmol dm(-3) up to the CMC, 8 mmol dm(-3), then quite rapidly decreased again down to -82 mV from the CMC to 10 mmol dm(-3), and finally stayed almost constant at -82 mV up to the concentration of 20 mmol dm(-3). The above variations of the surface potential cannot be elucidated by the conventional surface excess, and therefore, the new concept of surface adsorption was presented for a simple salt and a typical anionic surfactant.     

Sulfur extrusion with tin radical: synthesis of 4',5'-didehydro-5'-deoxy-5'-(tributylstannyl)adenosine, an intermediate for potential inhibitors against S-adenosyl homocysteine hydrolase

A new approach has been developed for the synthesis of potential inhibitors of S-adenosyl-l-homocysteine (AdoHcy) hydrolase. The key intermediate 9-[2,3-bis-O-(tert-butyldimethylsilyl)-5-(Z)-(tributylstannyl)-5-deoxy-beta-d-erythro-pent-4-enofuranosyl]adenine (12) was prepared by sulfur extrusion reaction of 4',5'-didehydro-5'-deoxy-5'-(phenylthio)adenosine (11) with tributyltin radical. It was found that this reaction proceeds stereoselectively, forming 12 irrespective of the geometry of 11. Compound 12 readily underwent iodination, bromination, and chlorination with retention of configuration, whereas fluorination gave both (Z)- and (E)-isomers of vinyl fluoride. Because of the susceptibility of 12 to protodestannylation, the (Z)-vinyl iodide (13), prepared in quantitative yield from 12, was used as a substrate for C-C bond formation. Various types of carbon substituents (phenyl, vinyl, trifluorovinyl, ethynyl, and cyano) were introduced to the 5'-position of the 5-deoxy-beta-d-erythro-pent-4-enofuranosyl structure to open up a new route to potential inhibitors of AdoHcy hydrolase.     

Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid-state 17O NMR spectroscopy and ab initio MO calculations

The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated.     

Precocentration method using an activatable yield tracer for neutron activation analysis

Previously, the use of an enriched stable isotope as an activatable yield tracer in preconcentration steps has been tested by use of commercially available enriched¹¹⁶Cd and¹⁵⁶Dy for biological standard reference materials.^1,2 In the present work, this method has been further applied to the determination of lanthanoid contents in various kinds of samples: one coal fly-ash, three Japanese standard rocks, and eight standard soils. Samples were decomposed by alkali fusion in the preconcentration step. Thirteen elements were determined for coal fly-ash and soil samples, and 14 elements for rocks. The data obtained for coal fly-ash and standard rocks are compared with the data reported in literature. The data for soil samples have been newly determined in the present work. The ordinary instrumental neutron activation analysis and radiochemical neutron activation analysis were also performed to confirm the accuracy and usefulness of the present method.     

Chemical conversion of uridine to 8,5′-O-cyclo-3-deazaguanosine

Treatment of 1-(2,3-O-isopropy lidene-β-D-ribofuranosyl)-2-oxo-4-imidazoline-4-carboxylic acid methyl ester with formaldehyde gave the 5-hydroxymethyl derivative which, after aeetylalion, gave the 5-eyanomelhyl derivative by treatment with tetra-n-butylammonium cyanide. The 2,5′-O-cyclo derivative of the 5-cyanomethylimidazole-4-carboxylate was converted to the title compound by treatment with ammonia. The present sequence of reactions furnished the chemical conversion of uridine to a 3-deazaguanosine via the imidazole nucleoside as the intermediate.     

Synthesis of 6-arylazo-substituted 5-hydroxy-2-hydroxymethyl-4-pyridones and related compounds

5-Hydroxy-2-hydroxymethyl-4-pyridone ( 1 ) and 5-hydroxy-2-hydroxymethyl-1-methyl-4-pyridone ( 2 ) reacted with arenediazonium salts to give 6-arylazo-substituted compounds 3a-d and 4a-d , respectively. Compounds 3a-d were methylated with diazomethane to afford 6-arylazo-2-hydroxymethyl-4,5-dimethoxypyridines 5a-d .