Chiral zinc(II) and copper(II)-catalyzed asymmetric ring-opening reactions of meso-epoxides with aniline and indole derivatives

The ring-opening reactions of meso-epoxides with aniline and indole derivatives proceeded smoothly in water in the presence of Zn(II) and Cu(II) surfactant-type catalysts to afford the corresponding products in moderate to high yields with good to excellent enantioselectivities. Opposite enantiomers were obtained by using Sc(III) and Zn(II) or Cu(II) with the same chiral ligand. Crystal structures of these catalysts may explain the reversal of the enantioselectivity. Some reactions were also tested in dichloromethane (DCM), and it was revealed that the reactions proceeded faster in water than in DCM. Finally, several non-linear effect experiments suggested unique structure of these chiral catalysts.     

Control of energy spread and dark current in proton and ion beams generated in high-contrast laser solid interactions

By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad. Numerical simulations suggest that expansion of the rear-side contaminant layer allowed for density conditions that prevented the protons from being screened from the sheath field, thus providing a low energy cutoff in the observed spectra normal to the target surface.     

Relaxation structure analysis of Li inserted γ-Fe2O3

γ-Fe₂O₃ has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe₂O₃, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe₂O₃ (x = 0.66, 1.1, 1.5 in terms of Li_XFe₂O₃), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe₂O₃ with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically.     

Spontaneous racemization and epimerization behavior in solution of chiral nitroxides

[reaction: see text] Enantiomerically enriched samples of chiral cyclic nitroxides with a 4-hydroxyphenyl group on the stereogenic center bearing the NO radical group undergo unprecedented spontaneous racemization and/or epimerization in aprotic solvents, which can be well accounted for by the multistep equilibrations involving planar quinoid intermediates.     

Internal delivery of soft chlorine and bromine atoms: stereoselective synthesis of (E)-beta-halogenovinyl(aryl)-lambda3-iodanes through domino lambda3-iodanation-1,4-halogen shift-fluorination of alkynes

4-(Difluoroiodo)toluene-induced domino lambda(3)-iodanation-1,4-halogen shift-ring enlargement-fluorination reaction of 5-halopentynes with a four-, five-, or six-membered carbocycle afforded the ring-expanded (E)-delta-fluoro-beta-halovinyl-lambda3-iodanes stereoselectively in high yields, probably via the intermediacy of five-membered halonium ions. Use of internal alkynes makes it possible to synthesize tetrasubstituted beta-halovinyl-lambda(3)-iodanes with defined stereochemistry.     

Volume reduction and tritium retention factor in electrolytic enrichment of water

Volume reduction(N), tritium retention factor (R), tritium concentration factor(Z) and apparent separation factor(beta) were measured on the large and small electrolytic cell systems. The relative variation of R was smaller than that of Z. So, it is recommended to use R in calculation of tritium concentrations in water samples. Furthermore, it was empirically revealed that R can be obtained only from N if a reliable beta-value is previously known. Therefore, it is possible to obtain R without electrolysis of the tritium standard solution. Taking into account the above facts, the so-called non-spike analysis of tritium, in which electrolytic enrichment and liquid scintillation counting are combined, becomes practicable.     

Hydrophobic indicators for two-phase titrations and their application to the determination of silver and pentachlorophenol

The hydrophobic dyes tetrabromophenolphthalein ethyl ester and 2,6-dichlorophenolindo-phenol are proposed as visual indicators for two-phase titrations. The aqueous phase is colourless throughout the titration and these indicators make it possible to detect the end-point of the titration by the colour of one or the other phase. The indicators allow the two-phase titration of the silver(I)-1,10-phenanthroline complex with tetraphenylborate and of pentachlorophenol with tetraphenylphosphonium chloride.     

Thermal extrusion of cellulose using hydroxypropyl methylcellulose

Cellulose - Hydroxypropyl methylcellulose (HPMC), a cellulose derivative, is highly water soluble, viscoelastic, and thermoplastic. However, the thermoplasticity of HPMC has not yet been studied in...     

Palladium-catalyzed allylic oxidation of olefins by t-butyl hydroperoxide and tellurium(IV) oxide

Treatment of several cyclic olefins, β-pinene, allylbenzene, and estragole with palladium(II) salt in acetic acid in the presence of t-butyl hydroperoxide and tellurium(IV) oxide afforded mainly the corresponding allylic acetates. The reaction proceeded catalytically with palladium(II) salt, t-BuOOH working as a reoxidizing agent.