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61.
Massoud S. Stephan Antonius J. J. M. Teunissen Gerard K. M. Verzijl Johannes G. de Vries 《Angewandte Chemie (International ed. in English)》1998,37(5):662-664
Environmentally benign and economical production of arylated olefins can be achieved by a new variant of the Heck reaction in which no halogen salts are formed. The trick is the use of aromatic carboxylic anhydrides 1 as arylating agents. With halide-activated palladium chloride as catalyst, which requires no phosphane ligands, the olefins 2 can be prepared according to Equation (a) in good yields. 相似文献
62.
Hans Bock Zdenek Havlas Delia Hess Christian Nther 《Angewandte Chemie (International ed. in English)》1998,37(4):502-504
Quite unexpectedly, all three electrons are taken up by the same anthryl moiety when 9,9′-bianthryl is reduced with an excess of sodium metal. Thanks to the “right” ligand/solvent mixture the first radical trianion salt (depicted on the right) could be isolated. It is a contact-ion quadruple of bianthryl in which all three Na+ counterions coordinate to the same half of the hydrocarbon molecule. 相似文献
63.
Hidetoshi Kawai Takanori Suzuki Masakazu Ohkita Takashi Tsuji 《Angewandte Chemie (International ed. in English)》1998,37(6):817-819
Benzene rings severely bent and closely stacked face-to-face are revealed in the crystal structure of the [1.1]paracyclophane derivative 1 , which could be isolated thanks to the kinetic stabilization provided by the steric shielding of the bridgehead sites by the substituents. 相似文献
64.
Chikako Matsuda Yuto Suzuki Prof. Dr. Hiroshi Katagiri Dr. Takashi Murase 《化学:亚洲杂志》2021,16(5):538-547
The intramolecular Diels−Alder reactions of helicenes deform their π-conjugated screw-shaped skeletons. In particular, terminally tetrafluorinated [7]helicene (F4-[7]helicene) undergoes a photoinduced Diels−Alder reaction followed by a photoinduced double fluorine atom transfer. Herein, we thoroughly investigated this photochemical domino process by decreasing the level of fluorine substitution. F3-[7]Helicenes bearing two fluorine atoms at the dienophile terminal underwent photoinduced Diels−Alder reactions, but the whole domino process became slow. F2-[7]Helicene, which is difluorinated only at the dienophile terminal, was also photolabile. As a result, two fluorine atoms were sufficient for the photochemical domino reaction to occur. X-ray crystallographic analysis revealed that F2-[7]helicene was less compressed than F4-[7]helicene, indicating that terminal polyfluorination enhanced the intramolecular arene−fluoroarene stacking interactions and thus promoted the transformations. 相似文献
65.
Influence of Halogen Substitution in the Ligand Sphere on the Antitumor and Antibacterial Activity of Half‐sandwich Ruthenium(II) Complexes [RuX(η6‐arene)(C5H4N‐2‐CH=N‐Ar)]+
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Joel M. Gichumbi Bernard Omondi Geraldine Lazarus Moganavelli Singh Nazia Shaikh Hafizah Y. Chenia Holger B. Friedrich 《无机化学与普通化学杂志》2017,643(11):699-711
New complexes [(η6‐p‐cymene)Ru(C5H4N‐2‐CH=N–Ar)X]PF6 [X = Br ( 1 ), I ( 2 ); Ar = 4‐fluorophenyl ( a ), 4‐chlorophenyl ( b ), 4‐bromophenyl ( c ), 4‐iodophenyl ( d ), 2,5‐dichlorophenyl ( e )] were prepared, as well as 3a – 3e (X = Cl) and the new complexes [(η6‐arene)RuCl(N‐N)]PF6 (arene = C6H5OCH2CH2OH, N‐N = 2,2′‐bipyridine ( 4 ), 2,6‐(dimethylphenyl)‐pyridin‐2‐yl‐methylene amine ( 5 ), 2,6‐(diisopropylphenyl)‐pyridin‐2‐yl‐methylene amine ( 6 ); arene = p‐cymene, N‐N = 4‐(aminophenyl)‐pyridin‐2‐yl‐methylene amine ( 7 )]. X‐ray diffraction studies were performed for 1a , 1b , 1c , 1d , 2b , 5 , and 7 . Cytotoxicities of 1a – 1d and 2 were established versus human cancer cells epithelial colorectal adenocarcinoma (Caco‐2) (IC50: 35.8–631.0 μM), breast adenocarcinoma (MCF7) (IC50: 36.3–128.8.0 μM), and hepatocellular carcinoma (HepG2) (IC50: 60.6–439.8 μM), 3a – 3e were tested against HepG2 and Caco‐2, and 4 – 7 were tested against Caco‐2. 1 – 7 were tested against non‐cancerous human epithelial kidney cells. 1 and 2 were more selective towards tumor cells than the anticancer drug 5‐fluorouracil (5‐FU), but 3a – 3e (X = Cl) were not selective. 1 and 2 had good activity against MCF7, some with lower IC50 than 5‐FU. Complexes with X = Br or I had moderate activity against Caco‐2 and HepG2, but those with Cl were inactive. Antibacterial activities of 1a , 2b , 3a , and 7 were tested against antibacterial susceptible and resistant Gram‐negative and ‐positive bacteria. 1a , 2b , and 3a showed activity against methicillin‐resistant S. aureus (MIC = 31–2000 μg · mL–1). 相似文献
66.
Dr. Gabriele Hierlmeier Dr. Paolo Tosatti Dr. Kurt Puentener Prof. Dr. Paul J. Chirik 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(3):e202216026
Treatment of phosphino(imino)pyridine (PIP) molybdenum cyclooctadiene (COD) complexes [(PIP)Mo(COD)] with dihydrogen in the presence of benzene selectively furnished the molybdenum cyclohexadienyl hydrides [(PIP)MoH(η5-C6H7)], which are precatalysts for the hydrogenation of benzene to cyclohexane. [(PIP)MoH(η5-C6H7)] arises from a rarely observed insertion of benzene into a molybdenum-hydride bond, a key step in the molybdenum-catalyzed homogeneous hydrogenation of arenes. The reaction with toluene afforded a single isomer of the corresponding molybdenum cyclohexadienyl hydride while para-xylene predominantly formed the molybdenum η6-arene complex with the insertion product being a minor component. Addition of carbon monoxide to a cyclohexane-d12 solution of [(PIP)MoH(η5-C6H7)] liberated cyclohexadiene, providing experimental support for a higher kinetic barrier for the subsequent steps en route to cycloalkanes. 相似文献
67.
Xinbei Du Mengke Ma Yahan Zhang Xiang Yu Longming Chen Han Zhang Zhao Meng Xueshun Jia Junyi Chen Qingbin Meng Chunju Li 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301857
Since bacteria in biofilms are inherently resistant to antibiotics and biofilm-associated infections pose a serious threat to global public health, new therapeutic agents and schemes are urgently needed to meet clinical requirements. Here two quaternary ammonium-functionalized biphen[n]arenes (WBPn, n=4, 5) were designed and synthesized with excellent anti-biofilm potency. Not only could they inhibit the assembly of biofilms, but also eradicate intractable mature biofilms formed by Gram-positive S. aureus and Gram-negative E. coli bacterial strains. Moreover, they could strongly complex a conventional antibiotic, cefazolin sodium (CFZ) with complex stability constants of (7.41±0.29)×104 M−1 for CFZ/WBP4 and (4.98±0.49)×103 M−1 for CFZ/WBP5. Combination of CFZ by WBP4 and WBP5 synergistically enhanced biofilm eradication performance in vitro and statistically improved healing efficacy on E. coli-infected mice models, providing a novel supramolecular strategy for combating biofilm-associated infections. 相似文献
68.
Claude Niebel 《Tetrahedron letters》2008,49(51):7276-7278
A general approach toward Janus diones involving the reaction of pyromellitic or naphthalenetetracarboxylic dianhydrides with ethyl(triphenylphosphoranylidene)acetate and subsequent rearrangement of the products is described. This approach allows avoiding the formation of poorly soluble intermediates, in which purity cannot be effectively controlled. Dicyclopenta[b,g]naphthalene-1,3,6,8(2H,7H)-tetraone 3, a promising precursor of molecular and polymeric advanced materials is described. 相似文献
69.
The first 4-chloro-1,3-bis(trimethylsilyloxy)-1,3-diene and its application to the regioselective synthesis of chlorinated arenes 总被引:1,自引:0,他引:1
Stefanie Reim 《Tetrahedron letters》2008,49(14):2329-2332
Chlorinated phenols, benzophenones, and butenolides are prepared by various one-pot cyclization reactions of the first 4-chloro-1,3-bis(trimethylsilyloxy)-1,3-butadiene. 相似文献
70.
Arasambattu K. Mohanakrishnan Vasudevan Dhayalan J. Arul Clement Ramalingam Balamurugan Radhakrishnan Sureshbabu Natarajan Senthil Kumar 《Tetrahedron letters》2008,49(41):5850-5854
A ZnBr2-mediated arylation of N-protected 2/3-bromomethylindoles containing an electron-deficient malonylidene unit with arenes at 80 °C led to the formation of arylated products, which on unprecedented 1,5-sigmatropic rearrangement followed by electrocyclization and subsequent aromatization with loss of diethylmalonate furnished the corresponding annulated carbazoles in reasonable yields. 相似文献