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91.
92.
Kazuhiko Semba Masataka Shinomiya Prof. Dr. Tetsuaki Fujihara Prof. Dr. Jun Terao Prof. Dr. Yasushi Tsuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7125-7132
The highly selective copper‐catalyzed hydroboration of allenes has been developed. Allylboranes and alkenylboranes were selectively prepared by the judicious choice of catalytic species (copper hydride and boryl copper). Furthermore, two types of alkenylboranes could be selectively synthesized by the choice of an appropriate ligand. Mechanistic studies confirmed that the protonation of a (Z)‐σ‐allyl copper species, which was isolated and structurally characterized by single‐crystal X‐ray diffraction, was a key step in these reactions. Besides allenes, this method is also applicable to the selective hydroboration of 1,3‐diene derivatives to afford allylboranes and homoallylboranes. 相似文献
93.
Prof. Takanori Suzuki Yuto Sakano Dr. Tomohiro Iwai Dr. Shinichi Iwashita Dr. Youhei Miura Dr. Ryo Katoono Prof. Hidetoshi Kawai Prof. Kenshu Fujiwara Prof. Yasushi Tsuji Prof. Takanori Fukushima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):117-123
When two benzene rings are fused to a tetraaryl‐o‐quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron‐donating alkoxy groups, 1 undergo reversible two‐electron oxidation to 2 2+, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec‐butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b 2+ and 2 c 2+, which represents an efficient method for enhancing circular‐dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X‐ray analysis of dication 2 2+ revealed π–π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response. 相似文献
94.
Ariaki Murata Ryota Akaike Tatsuya Kawahashi Ryo Tsuchiya Hiroyuki Takemoto Toshiyuki Ohnishi Yasushi Todoroki Nobuyuki Mase Mineyuki Yokoyama Kazuteru Takagi Peter Winterhalter Naoharu Watanabe 《Tetrahedron》2014
A flower-inducing compound, LDS1, was isolated from a free-floating aquatic plant, Lemna paucicostata. The chemical structure and the absolute stereochemistry of LDS1 were determined as (9R,13R,11E,15Z)-9,13-dihydroxy-10-oxooctadeca-11,15-dienoic acid for its most abundant diastereomer. LDS1 was enzymatically produced when the plant was exposed to drought stress, and induced flowering at a concentration of 10 nM. 相似文献
95.
The catalytic activities of the cationic synthetic flavin adduct 1 with various dendritic and non-dendritic 2,6-bis(acylamino)pyridines 2 were examined for the oxidation of organic sulfides with H2O2. The adduct of 5-ethyllumiflavinium perchlorate 1a with 2b–d bearing poly(benzyl ether) dendron units acts as an efficient organocatalyst for the oxidative transformation of sulfides to the corresponding sulfoxides under mild conditions. 相似文献
96.
Copper‐Catalyzed CH Bond Direct Chalcogenation of Aromatic Compounds Leading to Diaryl Sulfides,Selenides, and Diselenides by Using Elemental Sulfur and Selenium as Chalcogen Sources Under Oxidative Conditions
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Prof. Fumitoshi Shibahara Takafumi Kanai Eiji Yamaguchi Akika Kamei Takayuki Yamauchi Prof. Toshiaki Murai 《化学:亚洲杂志》2014,9(1):237-244
The reactions of aromatic compounds and elemental chalcogens catalyzed by a copper salt with molecular oxygen as an oxidant were carried out. The reaction of 3‐substituted imidazo[1,5‐a]pyridines and elemental sulfur in the presence of CuTC (copper(I) thiophenecarboxylate) gave the corresponding bisimidazopyridyl sulfides in good to quantitative yields. The reaction proceeded even under aerobic oxidation conditions. The use of a polar solvent was crucial for the reaction, and DMSO (dimethyl sulfoxide) in particular stimulated the reaction. The reaction could be applied to common aromatic compounds, such as N‐methyl indole and dialkyl anilines. The reaction of indole proceeded at the nucleophilic C3 position rather than at the acidic C2 position. In addition, the reaction of dialkyl anilines proceeded with an ortho, para orientation. The reactions of imidazopyridines and elemental selenium under similar conditions gave the corresponding bisimidazopyridyl diselenides along with bisimidazopyridyl monoselenides. The resulting diselenides were readily converted to the corresponding monoselenides with unreacted imidazopyridines under the same conditions. The reaction could be applied to the copolymerization of bifunctional bisimidazopyridines and elemental sulfur to give oligomeric copolymers in quantitative yield. 相似文献
97.
98.
We report ellipticity dependence of high-order harmonic generation (HHG) from aligned N2, O2, and CO2 molecules. Experimentally, we find that the ellipticity dependence is sensitive to molecular alignment and to the shape and symmetry of the valence orbitals. It is also found that the destructive interference in the recombination process affects the ellipticity dependence. Theoretically, we extend the original Lewenstein model to a more generalized model, which can be applicable to HHG from molecules, by introducing an electron acceleration parameter xi(theta) and by combining the molecular orbital method. The present observations are successfully explained by our model. 相似文献
99.
We demonstrate an optical parametric chirped-pulse amplification (OPCPA) system with the pulse energy of 1.5 mJ at a 1 kHz repetition rate. The newly developed 100 ps Ti:sapphire pump laser system, which was optically synchronized with OPCPA seed pulses, delivered 10 mJ, 400 nm pump pulses. After three-stage parametric amplification, recompression of the amplifier output from 45 ps to 6.4 fs was performed. The pulse width of 6.4 fs is, to our knowledge, the shortest ever obtained by OPCPA, and the average power of 1.5 W (1.5 mJ, 1 kHz) is believed to be the highest among few-cycle OPCPA systems. 相似文献
100.
N. Kuroda S. Ulmer D. J. Murtagh S. Van Gorp Y. Nagata M. Diermaier S. Federmann M. Leali C. Malbrunot V. Mascagna O. Massiczek K. Michishio T. Mizutani A. Mohri H. Nagahama M. Ohtsuka B. Radics S. Sakurai C. Sauerzopf K. Suzuki M. Tajima H. A. Torii L. Venturelli B. Wünschek J. Zmeskal N. Zurlo H. Higaki Y. Kanai E. Lodi Rizzini Y. Nagashima Y. Matsuda E. Widmann Y. Yamazaki 《Hyperfine Interactions》2015,235(1-3):13-20
In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected. 相似文献