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排序方式: 共有176条查询结果,搜索用时 15 毫秒
1.
Koichi Mikami Yukinori Yusa Manabu Hatano Kazuki Wakabayashi Kohsuke Aikawa 《Tetrahedron》2004,60(20):4475-4480
A tropos rhodium(I) complex having skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric ene-type carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers or spiro-rings. 相似文献
2.
Alkyl radicals, derived from decarboxylation of carboxylic acids, add readily to phenyl vinyl sulphone and vinyl phosphonium bromide. The adducts may be further converted into a variety of useful synthetic intermediates. 相似文献
3.
An operationally simple, inexpensive, efficient, and environmentally friendly esterification of various carboxylic acids, phosphonic acids, and phosphinic acids with triethyl orthoacetate or trimethyl orthoacetate under neutral conditions in a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, was successfully carried out to provide the corresponding ethyl esters or methyl esters in high yields. 相似文献
4.
A system involving two polymer-supported reagents for the selective and organocatalytic oxidation of alcohols to aldehydes or ketones has been developed in which both polymeric reagents can be recovered and reused. 相似文献
5.
A simple method for the diastereoselective synthesis of racemic 1,2-diol mediated by low-valence niobium generated in situ is described. A 1,4-dioxane-toluene solvent system was found to be essential to achieve higher selectivities and to prevent other reactions of pinacols, such as deoxygenation and acetal formation. Aromatic aldehydes and ketones were converted to the corresponding pinacols with up to 97 and 85% de, respectively. 相似文献
6.
7.
Hideaki Hioki Yumiko Ohnishi Miwa Kubo Emi Nashimoto Yukinori Kinoshita Miho Samejima Mitsuaki Kodama 《Tetrahedron letters》2004,45(3):561-564
A fluorescence-labeled calix[4]arene library substituted with peptides at the upper rim was synthesized. Screening of the library for binding a dye-labeled oligopeptide indicated that some peptidocalix[4]arenes selectively bind the oligopeptide. The chemosensitivity of the library members for a target peptide was also investigated. 相似文献
8.
Iodophosphoryloxylation of carbon-carbon multibonds was attempted. Alkynes and cyclohexene were converted to the corresponding 1,2-iodophosphoryloxylated compounds in moderate to good yields with a trivalent iodine compound/iodine system, while glucal gave mainly the corresponding iodohydrin compound in this system. However, 2-deoxy-2-iodoglycosyl diphenylphosphinates were obtained from the corresponding glycals with a diphenylphosphinic acid/iodine/potassium carbonate system in good yields. Moreover, triethylborane smoothly reduced 2-deoxy-2-iodoglycosyl diphenylphosphinates to 2-deoxyglycosyl diphenylphosphinates in a 1,4-cyclohexadiene solvent. 相似文献
9.
10.
Takahiro Gunji Yukinori Nagao Takahisa Misono Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》1992,30(3):371-377
From polytitanosiloxanes (PTS), SiO2–TiO2 oxide fibers with fairly good tensile strength were prepared, and their mechanical and thermal properties were investigated. The precursor fibers PTS-0.5 and PTS-1.0 were obtained by dry spinning of a highly viscous PTS solution which were formed as the reaction mixture of silicic acid (SA) with bis(2,4-pentanedionato)titanium diisopropoxide (PTP) in the molar ratios (SA/PTP) of 0.5 and 1.0. The precursor fibers PTS-0.5 were too brittle to measure their tensile strength, whereas PTS-1.0 and the heat-treated fibers were found to have tensile strength of 130 (precursor), 540 (500°C), and 450 (900°C) MPa, respectively. Heat-treatment of the fibers PTS-1.0 at above 1000°C forms anatase and rutile of titanium dioxide. The crystallization is resulted from the unreacted PTP which is not incorporated into the polymer network. 相似文献