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91.
The reaction of zirconium n-propoxide in glycol at 300°C yielded microcrystalline tetragonal zirconia (ZrO2). The crystallite size of the product depended on the carbon number of the glycol and increased in the following order (carbon
number of glycol): 2<6<4, which suggested that the heterolytic cleavage of O-C bond of gylcoxide formed by transesterification
is the prime factor for the formation of the product. In toluene, zirconium isopropoxide also gave tetragonal zirconia at
300°C, and zirconium tert-butoxide decomposed at 200°C yielding amorphous zirconia, while zirconium n-propoxide was stable at 300°C. These results suggest that the reaction in toluene depends on the structure of the alkyl group
of the alkoxides. Thus-obtained tetragonal zirconias maintained large surface areas (90–160 m2/g) even after calcination at 500°C. 相似文献
92.
The sequence Fourier analysis reported previously seems to be applicable to elucidating a simple and concerted interaction in Arabidopsis thaliana, similar to that in Homo sapiens. 相似文献
93.
In this paper, we consider the expected probabilities of misclassification (EPMC) in the linear discriminant function (LDF) based on two-step monotone missing samples and derive an asymptotic approximation for the EPMC with an explicit form for the considered LDF. For this purpose, we also provide some results of the expectations for the inverted Wishart matrices in this paper. Finally, we conduct the Monte Carlo simulation for evaluating our result. 相似文献
94.
Kitagawa O Takahashi M Yoshikawa M Taguchi T 《Journal of the American Chemical Society》2005,127(11):3676-3677
In the presence of (R)-DTBM-SEGPHOS-Pd(OAc)2 catalyst, N-arylation of ortho-tert-butyl-NH-anilides with 4-nitroiodobenzene proceeds with high enantioselectivity (89-95% ee) to give optically active atropisomeric anilides possessing N-C chiral axis. Furthermore, the intramolecular version of the present catalytic asymmetric N-arylation gave atropisomeric lactams with high optical purity (94-96% ee). 相似文献
95.
Soloshonok VA Cai C Yamada T Ueki H Ohfune Y Hruby VJ 《Journal of the American Chemical Society》2005,127(43):15296-15303
This paper describes a systematic study of addition reactions between the chiral Ni(II) complex of the Schiff base of glycine with (S)-o-[N-(N-benzylprolyl)amino]benzophenone and (S)- or (R)-3-[(E)-enoyl]-4-phenyl-1,3-oxazolidin-2-ones as a general and synthetically efficient approach to beta-substituted pyroglutamic acids and relevant compounds. These reactions were shown to occur at room temperature in the presence of nonchelating organic bases and, most notably, with very high (>98% diastereomeric excess (de)) stereoselectivity at both newly formed stereogenic centers. The stereochemical outcome of the reactions was found to be overwhelmingly controlled by the stereochemical preferences of the Michael acceptors, and the chirality of the glycine complex influenced only the reaction rate. Thus, in the reactions of both the (S)-configured Ni(II) complex and the Michael acceptors, the reaction rates were exceptionally high, allowing preparation of the corresponding products with virtually quantitative (>98%) chemical and stereochemical yields. In contrast, reactions of the (S)-configured Ni(II) complex and (R)-configured Michael acceptors proceeded at noticeably lower rates, but the addition products were obtained in high diastereo- and enantiomeric purity. To rationalize the remarkably high and robust stereoselectivity observed in these reactions, we consider an enzyme-substrate-like mode of interaction involving a topographical match or mismatch of two geometric figures. Excellent chemical and stereochemical yields, combined with the simplicity and operational convenience of the experimental procedures, render the present method of immediate use for preparing various beta-substituted pyroglutamic acids and related compounds. 相似文献
96.
Miura T Goto K Waragai H Matsumoto H Hirose Y Ohmae M Ishida HK Satoh A Inazu T 《The Journal of organic chemistry》2004,69(16):5348-5353
The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS. 相似文献
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Ion exchange fabric (IEF) having the functional group of sulfonic acid was synthesized by radiation grafting of glycidyl methacrylate on a polyethylene nonwoven fabric and subsequent chemical modification. Total organic carbon eluted from the resulting IEF could be reduced to the concentration less than 1 ppb after washing with organic solvents. Adsorption performance of the obtained IEF was evaluated by 10 ppb Na+ solution. The column packed IEF, 7 mm in diameter and 20 mm high, could remove the Na+ at the distribution coefficient of 1.2×107 at linear velocity of 400 m/h. At column height of 95 mm, the breakthrough point reached 2.0×105 in bed volume and the degree of column utilization was improved up to 18.7%. From these results, the IEF synthesized by graft polymerization was considered to be applicable for water purification in ultra-pure water production. 相似文献