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排序方式: 共有235条查询结果,搜索用时 187 毫秒
91.
92.
Yoshiharu Ishikawa Norihisa Kato Shigeyuki Suematsu Tokihiro Kuroyanagi 《Nuclear Physics A》1982,380(3)
In the experiments on 74Ge(d, pγ)75Ge, a 52.5±0.1 keV γ-ray was found in 75Ge with a half-life of 216±5 ns. From the analysis of the γ-ray spectra the conversion coefficient of the 52.5 keV γ-ray was determined. Then, a new level of
is confirmed to exist at 192.5 keV. The reduced transition probabilities of the 52.5 keV transition are deduced to be (6.9+5.6 −2.1) × 10−5 for B(M1) and 31+3 −2 for B(E2) in Weisskopf units. 相似文献
93.
94.
Shigeyuki Yoshifuji Hideyo Matsumoto Ken-ichi Tanaka Yoshihiro Nitta 《Tetrahedron letters》1980,21(31):2963-2964
The ruthenium tetroxide oxidation of N-acyl-l-proline esters gave the corresponding l-pyroglutamic acid derivatives in good yields with no appreciable racemization, which led to the first chemical conversion of l-proline to l-glutamic acid. 相似文献
95.
96.
Masaoka S Akiyama G Horike S Kitagawa S Ida T Endo K 《Journal of the American Chemical Society》2003,125(5):1152-1153
Novel Cu(I) complexes containing a mu2-eta2,eta2-type benzoquinone ligand have been synthesized and crystallographycally characterized. These complexes are synthesized by the redox reaction of a copper-quinonoid pair and may indicate a significant intermediate in the Cu-BQ catalytic system. Moreover, this study is regarded as one of the good examples in the Cu(I)-olefin family of enhanced pi-back-donation. 相似文献
97.
Hiromu Fuse Hiroyasu Nakao Yutaka Saga Arisa Fukatsu Mio Kondo Shigeyuki Masaoka Harunobu Mitsunuma Motomu Kanai 《Chemical science》2020,11(44):12206
Hydroxyalkylation of N-heteroaromatics with aldehydes was achieved using a binary hybrid catalyst system comprising an acridinium photoredox catalyst and a thiophosphoric acid organocatalyst. The reaction proceeded through the following sequence: (1) photoredox-catalyzed single-electron oxidation of a thiophosphoric acid catalyst to generate a thiyl radical, (2) cleavage of the formyl C–H bond of the aldehyde substrates by a thiyl radical acting as a hydrogen atom transfer catalyst to generate acyl radicals, (3) Minisci-type addition of the resulting acyl radicals to N-heteroaromatics, and (4) a spin-center shift, photoredox-catalyzed single-electron reduction, and protonation to produce secondary alcohol products. This metal-free hybrid catalysis proceeded under mild conditions for a wide range of substrates, including isoquinolines, quinolines, and pyridines as N-heteroaromatics, as well as both aromatic and aliphatic aldehydes, and tolerated various functional groups. The reaction was applicable to late-stage derivatization of drugs and their leads.Hydroxyalkylation of N-heteroaromatics with aldehydes was achieved using a binary hybrid catalyst system comprising an acridinium photoredox catalyst and a thiophosphoric acid organocatalyst. 相似文献
98.
Yoshiyuki Oishi Shigeyuki Harada Masa-Aki Kamimoto Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1989,27(10):3393-3403
New fluorine-containing aromatic polyamides with inherent viscosities of 0.4–1.8 dL/g were prepared by the low temperature solution polycondensation of tetrafluoroisophthaloyl and tetrafluoroterephthaloyl chlorides with N,N′-bis(trimethylsilyl)-substituted aromatic diamines. The aromatic polyperfluoroisophthalamides were amorphous polymers with glass transition temperatures around 280°C, whereas the polyperfluoroterephthalamides were crystalline. Most of these aromatic polyamides were soluble in organic solvents, and began to decompose around 330°C in air or nitrogen atmosphere. 相似文献
99.
100.
The first total synthesis of ankorine (4), an Alangium lamarckii alkaloid, has been accomplished in the form of a recemic modification by means of an initial condensation of 2-benzyloxy-3,4-dimethoxyphenacyl bromide with the lactim ether 6, derived from ethyl (±)-trans-5-ethyl-2-oxo-4-piperidineacetate (5), and succeeding steps proceeding through the intemediates 7a, 8a, 9a, 10a (X=Cl), 11a, and 12a. A parallel synthetic route starting with 3,4,5-trimethoxyphenacyl bromide and 6 gave (±)-11-methoxyprotoemetinol (12c) via the intermediates 7c, 8c, 9c, 10c (X =I,ClO4), and 11c. The trimethyl ether 12c did not match the O-Me derivative (type 12e) of natural ankorine. Thus, the formula 4 defines the structure and relative stereochemistry of ankorine. 相似文献