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It was found that 1,2-trifluoromethylation reactions of ketones, enones, and aldehydes were easily accomplished using the Prakash reagent in the presence of catalytic amounts of cesium carbonate, which represents an experimentally convenient, atom-economic process for this anionic trifluoromethylation of non-enolisable aldehydes and ketones.

A study of diffusivity of [Er.sup.3+] into LiNb[O.sub.3] crystal as a function of [Li.sub.2]O content and crystal orientation is described. The results obtained from X-cut and Z-cut congruent substrates treated with Li-rich vapor transport equilibration (VTE) technique showed that the [Er.sup.3+] diffusivity decreased monoexponentially with the increase in the [Li.sub.2]O content.

A palladium-catalyzed intramolecular direct arylation reaction of o-bromoaryl phosphine oxides was developed to afford a variety of P-stereogenic phosphole oxides in good yields. The enantioselectivities were closely associated with the specific structures of substrates, which ranged from 4-94%. As a result of ready availability of starting materials and simple operation to improve the enantioselectivities of the products with low ee values, the method provides a simple and straightforward procedure for the synthesis of P-stereogenic phosphole oxides. [ABSTRACT FROM AUTHOR]

It was found that 1,2-trifluoromethylation reactions of ketones, enones, and aldehydes were easily accomplished using the Prakash reagent in the presence of catalytic amounts of cesium carbonate, which represents an experimentally convenient, atom-economic process for this anionic trifluoromethylation of non-enolisable aldehydes and ketones. [ABSTRACT FROM AUTHOR]

It was found that the cinchona-derived primary amines and their combined catalyst systems with chiral organic acid or Lewis acid have been successfully applied in the cross-aldol reaction of trifluoromethyl ketones and aliphatic ketones. Excellent yields and good enantioselectivities (up to 89% ee) of the resulting β-trifluoromethyl-β-hydroxy ketones were obtained in the chiral primary amine catalyzed cross-aldol reaction under different conditions, which also led to both enantiomers of the desired products. This study also demonstrated the importance of synergistic effect of chiral organic acid on the primary amine catalysis. [ABSTRACT FROM AUTHOR]

Surface etching of a MgO-doped LiNbO3 crystal is demonstrated by annealing a sandwich structure formed by Mg:LiNbO3/Ti film/Mg:LiNbO3 at 1050-1100°C in a wet 02 atmosphere. The etching depth, raised Ti layer height and surface roughness were studied as a function of initial Ti film thickness, annealing temperature, and duration. The results show that the maximum etching depth can reach 260 nm while the surface roughness is <5 nm. The features of the raised Ti layer height and surface roughness of the etched surface and raised Ti layer are discussed on the basis of the Ti diffusion mechanism. Combined studies of X-ray single-crystal diffraction, Raman scattering, energy-dispersive X-ray, waveguiding characteristics, surface refractive index, and secondary-ion mass spectrometry show that the etched surface not only retains the LiNbO3 crystalline phase and the original crystal composition but is also Ti-free. An etching mechanism based upon an electrochemical reaction process is proposed. The MgO doping effect on the etching rate and surface roughness is discussed and explained in terms of the MgO doping effect on Ti solubility. A comparison of the +Z and -z surface etching is made. Finally, the present method is compared with other etching techniques and its possible application is suggested. [ABSTRACT FROM AUTHOR]

The feasibility of preparing locally Er-doped near-stoichiometric (NS) LiNbO3 crystals for integrated optics applications is demonstrated by a two-step process with standard diffusion (1130°C/154 h) of Er metal followed by vapor transport equilibration (VTE) treatment under three different conditions of 1135°C/22 h, 1115°C/50 h, and 1125°C/60 h. Detailed studies on the crystalline phase, Li composition, diffused surface roughness, and emission characteristics of Er3+ ions indicate that there is an upper limit on the initial Er metal film thickness: ∼20 nm for an X-cut crystal and ∼30 nm for a Z-cut crystal. When the initial Er film thickness is below this limit, the post-VTE does not induce formation of ErNbO4 precipitate and the diffused surface retains high quality with a root mean square roughness <3 nm. Depending on the VTE condition adopted, the VTE results in the increase of ([Li]+[Er])/[Nb] ratio in the diffused layer from congruent point (94.5%) to 97.4%–99.4%. Secondary ion mass spectrometry study shows that the post-VTE does not affect the Gauss nature of the Er profile, but leads to the increase of diffusion depth by as much as 1.6 μm. In comparison with the standard Er diffusion, the post-VTE results in the decrease of Er diffusivity by three to nine times. The higher the VTE temperature is, the lower the Er diffusivity is. In addition, the post-VTE also results in definite reduction of OH− content in crystal, slight lengthening of lifetime and slight narrowing of linewidth of Er3+ emission at 1530 nm. [ABSTRACT FROM AUTHOR]

X- and Z-cut off-congruent LiNbO 3(LN) crystals for use for integrated optics were prepared by carrying out Li-poor vapor transport equilibration (VTE) treatment on 1-mm-thick congruent plates at 1100 °C for durations ranging from 65 to 170 h. The Li 2O contents and crystalline phase in these Li-poor VTE-treated crystals were characterized by using Raman scattering, optical absorption, and powder X-ray diffraction spectroscopy. The studies of optical absorption in the ultraviolet region show that the Li-poor VTE treatments result in different extents of red-shifts of the optical absorption edges (OAEs), and the amount of the red-shift increases with the prolonged VTE duration. The mean Li 2O contents in all VTE samples were evaluated from the measured OAEs. The results show that the VTE-induced reduction of the mean Li 2O content can reach as much as ∼1 mol% for both cases of X-cut and Z-cut, and the mean Li 2O content and the VTE duration follows the linear relations: cLi= (48.62 ± 0.06) − (0.0052 ± 0.0004) tfor the X-cut crystals and cLi= (48.53 ± 0.08) − (0.0063 ± 0.0005) tfor the Z-cut crystals. The out-diffusion of Li shows a slight anisotropy. The diffusivity in a Z-cut crystal is slightly larger. The results of visible absorption, Raman scattering, and powder X-ray diffraction show that all the VTE crystals still retain the LiNbO 3phase, consistent with the result predicted from the LiNbO 3phase diagram. The critical VTE duration, longer than which the VTE will induce LiNb 3O 8phase in the crystal, is roughly evaluated to be about 577 and 476 h for an X-cut and a Z-cut plate, respectively. [ABSTRACT FROM AUTHOR]