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排序方式: 共有249条查询结果,搜索用时 15 毫秒
91.
Hagiwara K Sei Y Akita M Yoshizawa M 《Chemical communications (Cambridge, England)》2012,48(62):7678-7680
A novel tubular macrocycle containing four anthracene panels covalently linked by meta-phenylene spacers was synthesized. The tube is approximately 1 nm long with anthracene panels delimiting a columnar cavity with a diameter of ~1 nm and exhibits strong blue fluorescence. 相似文献
92.
The addition of 4?eq of chloral to osmundalactone (4S,5R)-4 gave quantitative formation of the hemiacetal derivative (4S,5R)-8, which was treated with methane sulfonic acid to afford the intramolecular Micheal addition product (+)-(3S,4S,5R)-9 possessing a 3,4-cis-dihydroxy-δ-lactone in 78% overall yield from (4S,5R)-4. The obtained (+)-(3S,4S,5R)-9 was subsequently converted to methyl D-digitoxoside (pyranoside) (12) in 13% overall yield and methyl D-digitoxoside (furanoside) (12) in 20% overall yield. The reaction of benzyl-osmundalactone (4R,5S)-3 and MeOH in the presence of Amberlyst A-26 as a basic catalyst gave 3,4-trans-δ-lactone (-)-(3S,4R,5S)-20 in 28% yield and 3,4-cis-δ-lactone (-)-(3R,4R,5S)-21 in 45% yield. Dibal-H reduction of (-)-(3S,4R,5S)-20 followed by catalytic hydrogenation gave L-oleandrose (6) in 86% overall yield, while Dibal-H reduction of (-)-(3R,4R,5S)-21 followed by catalytic hydrogenation provided L-cymarose (7) in 85% overall yield. 相似文献
93.
Li Z Kishi N Yoza K Akita M Yoshizawa M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8358-8365
An isostructural series of M(2)L(4) molecular capsules quantitatively self-assembled from two M(II) ions (M=Zn, Cu, Pt, Pd, Ni, Co, and Mn) and four bent ligands with embedded anthracene fluorophores. X-ray crystallographic analysis (for M=Zn, Cu, Ni, and Pd) confirmed the formation of closed-shell structures in which the large interior cavities inside the molecular capsules (about 1 nm) were shielded by eight anthracene panels. Analysis of the Zn(II) and Cu(II) structures showed the inclusion of an unusual triad guest cluster; four MeCN molecules, one water molecule, and one CF(3)SO(3)(-) ion were located inside the cavities. Full characterization by NMR spectroscopy and MS (ESI-TOF) demonstrated that the molecular capsules were quite stable and persist in solution. The fluorescence properties of the isostructural capsules were strongly dependent on the identity of the metal species: the Zn(II) capsule emitted strong blue fluorescence with a high quantum yield (Φ=0.8), in sharp contrast to the weakly emissive Ni(II) and Mn(II) capsules and the completely non-emissive Pd(II), Pt(II), and Co(II) capsules. On the other hand, the Cu(II) capsule exhibited solvatochromism and solvent-dependent emission behavior; blue emission of the capsule was "on" in DMSO but "off" in MeCN. 相似文献
94.
Kyosuke Matsumoto Shunsuke Kusaba Yuya Tanaka Yoshihisa Sei Munetaka Akita Kazushi Aritani Masa‐aki Haga Michito Yoshizawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8551-8555
Synthesis of molecular containers capable of incorporating multiple fullerenes remains challenging. Reported here is that room‐temperature mixing of metal ions with W‐shaped bispyridine ligands featuring polyaromatic panels results in the quantitative formation of a peanut‐shaped M2L4 capsule. The capsule reversibly converts into two molecules of an ML2 double tube in response to changes in the solvent. Notably, the capsule allows the incorporation of two fullerene molecules into the connected two spherical cavities at room temperature. The close proximity yet non‐contact of the encapsulated C60 molecules, with a separation of 6.4 Å, was revealed by X‐ray crystallographic analysis. The resultant, unusual fullerene dimer undergoes sequential reduction within the capsule to generate (C60.?)2, C60.??C602?, and (C602?)2 species. Furthermore, temperature‐controlled stepwise incorporation of two C60 molecules into the capsule is demonstrated. 相似文献
95.
Yasuo Akita Hideta Kanekawa Tatsuya Kawasaki Ikuko Shiratori Akihiro Ohta 《Journal of heterocyclic chemistry》1988,25(3):975-977
By the coupling reactions of trimethylsilylacetylene and 2-chloro-3,6-diisobutylpyrazine, 3,6-diisobutyl-2-trimethylsilylethynylpyrazine or 1,2-bis(3,6-diisobutylpyrazin-2-yl)acetylene was obtained, depending on the solvent used. The former substance coupled with various aryl and heteroaryl halides to give 1-aryl-2-pyrazin-ylacetylenes. 相似文献
96.
97.
Pairs of isomeric heterodinuclear complexes, [(cod)Ir(mu-PNNN)M(L)]BF4 and [(L)M(mu-PNNN)Ir(cod)]BF4, with switched metal arrangements are prepared in a specific manner by simply changing the addition order of the reagents. 相似文献
98.
Palladium-catalyzed cyclization-methoxycarbonylation of (2R,3S)-3-methylpenta-4-yne-1,2-diol (6) derived from (2R,3S)-epoxy butanoate 7 followed by methylation gave the tetrahydro-2-furylidene acetate (−)-10, which was converted to the left-half aldehyde (+)-3. A Wittig reaction between (+)-4 and the phosphoranylide derived from the bithiazole-type phosphonium iodide 4 using lithium bis(trimethylsilyl)amide afforded the (+)-cystothiazole A (2). 相似文献
99.
Yuya Tanaka Yuya Kato Kaho Sugimoto Reo Kawano Tomofumi Tada Shintaro Fujii Manabu Kiguchi Munetaka Akita 《Chemical science》2021,12(12):4338
Here, we report multinuclear organometallic molecular wires having (2,5-diethynylthiophene)diyl-Ru(dppe)2 repeating units. Despite the molecular dimensions of 2–4 nm the multinuclear wires show high conductance (up to 10−2 to 10−3G0) at the single-molecule level with small attenuation factors (β) as revealed by STM-break junction measurements. The high performance can be attributed to the efficient energy alignment between the Fermi level of the metal electrodes and the HOMO levels of the multinuclear molecular wires as revealed by DFT–NEGF calculations. Electrochemical and DFT studies reveal that the strong Ru–Ru interaction through the bridging ligands raises the HOMO levels to access the Fermi level, leading to high conductance and small β values.Multinuclear organometallic molecular wires having (diethynylthiophene)diyl-Ru(dppe)2 repeating units show high conductance with small attenuation factors. The strong Ru–Ru interaction is the key for the long-range carrier transport. 相似文献
100.