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71.
Robert Weis Reto Brun Robert Saf Werner Seebacher 《Monatshefte für Chemie / Chemical Monthly》2003,134(7):1019-1026
Summary. 4-Aminobicyclo[2.2.2]octanones which were prepared in one-pot-reactions from benzylidene acetone and dialkylammonium rhodanides
were reduced stereoselectively to their corresponding alcohols. The activities of the bicyclic compounds against causative
organisms of tropical deseases were examined. The 4-aminobicyclo[2.2.2]octan-2-ols were in general more active against Trypanosoma b. rhodesiense and Plasmodium falciparum than the corresponding keto compounds.
Corresponding author. E-mail: robert.weis@uni-graz.at
Received November 27, 2002; accepted December 2, 2002
Published online May 2, 2003 相似文献
72.
Elke Barsties Stefan Schaible Marc-Heinrich Prosenc Ursula Rief Werner Rll Oliver Weyand Birgit Dorer Hans-Herbert Brintzinger 《Journal of organometallic chemistry》1996,520(1-2):63-68
Bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (2-(CH3)2N-C9H6)2ZrCl2, and dimethylsilyl-bridged bis(2-N,N-dimethylamino-indenyl) zirconium dichloride, (CH3)2Si(2-(CH3)2N-C9H5)2ZrCl2, were prepared by reaction of the corresponding ligand lithium salts with ZrCl4 in toluene. Diffractometric structure determinations reveal C2-symmetric complex geometries for both complexes. An increased electron density at the Zr center of the dimethylamino-substituted complexes is indicated by reduction potentials which are 0.3–0.4 V more negative than those of their unsubstituted analogs. When activated with methyl aluminoxane in toluene solution, (CH3)2Si(2-(CH3)2N-C9H5)2ZrCl2 catalyzes the polymerization of propene to polymers with a microstructure comparable with that of polymers produced with other Me2Si-bridged bis(indenyl)ZrCl2 complexes, but with a substantially increased fraction of i-propyl end groups derived from alkyl exchange between Zr-polymer and Al---Me species. 相似文献
73.
Summary The calculation of electronically excited states with the internally contracted multiconfiguration-reference configuration interaction (CMRCI) method is discussed. A straightforward method, in which contracted functions for all states are included in the basis, is shown to be very accurate and stable even in cases of narrow avoided crossings. However, the expense strongly increases with the number of states. A new method is proposed, which employs different contracted basis sets for each state, and in which eigensolutions of the Hamiltonian are found using an approximate projection operator technique. The computational effort for this method scales only linearly with the number of states. The two methods are compared for various applications.Dedicated in honor of Prof. Klaus Ruedenberg 相似文献
74.
Gröger H Hummel W Buchholz S Drauz K Nguyen TV Rollmann C Hüsken H Abokitse K 《Organic letters》2003,5(2):173-176
[reaction: see text] An enzyme-compatible biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration has been developed. In this biphasic reaction media, which is advantageous for reactions at higher substrate concentrations, both enzymes (alcohol dehydrogenase and FDH from Candida boidinii) remain stable. The reductions with poorly water-soluble ketones were carried out at substrate concentrations of 10-200 mM, and the optically active (S)-alcohols were formed with moderate to good conversions and with up to >99% ee. 相似文献
75.
R. Werner Soukup 《Monatshefte für Chemie / Chemical Monthly》2005,13(1):803-818
Chemists have always defined the properties of materials on the basis of the changes observed when they reacted with other substances. Whereas this approach led chemists to relational concepts such as affinity, acid, and oxidant, physicists made measurements of objects they considered unchanged, determining their mass, charge, dipole moment, etc. In the middle of the 18th century, the Jesuit Josip Ruder Bocovi started thinking about the way in which atoms might be present in crystals, introducing a new concept according to which atoms in condensed phases represented punctual centres of attracting and repelling forces. Josef Loschmidt became aware of these ideas through the philosopher J. F. Herbart, and it is to Loschmidt that we owe the first representation of bonds as atomic spheres penetrating one another. The term quantum chemistry was first used by the physicist Arthur Erich Haas, who was born in Brno. However, Hans Hellmann (1903–1938) was the true founder of quantum chemistry. Hellmann, who was shot in Moscow in 1938, was the first person to realize the quantum-physical effect that leads to the chemical bond. In the 1960s K. Ruedenberg and others took theory a stage further when – thanks to the concept of the localized electron pair – they realized that the different approaches to the phenomenon of the chemical bond taken by chemists and physicists were largely comparable. This made it possible to bring the differing standpoints largely into line with one another. 相似文献
76.
[reaction: see text] A systematic investigation on a broad set of aldehydes reveals that the lifetimes of (Z)-photoenols can be modulated by variation of the substituents. We have found that the lifetimes of (Z)-enols (in benzene) can be varied by more than 1 order of magnitude with a judicious choice of the substituents that exert mesomeric and inductive effects as, for example, in the case of pentamethylbenzaldehyde (tau = 35 ns) and dicyanomesitaldehyde (tau = 760 ns). This study thus points to the fact that the electronic factors in conjunction with hydrogen bonding stabilization can considerably broaden the uni- as well as bimolecular chemistry based on photoenolization. Further, we have shown that the photoenols exhibit dramatic shifts in their absorption properties with variation of the substituents; although the photoenols have long been considered to be colored, their absorption properties have not been heretofore comprehensively examined. 相似文献
77.
Basic metals. XXIV. Mono- and dinuclear cobaltthiolato complexes obtained from disulfides. Splitting of a S? S bond by a metal base The dinuclear complex C5H5(PMe3)Co(μ-CO)2Mn(CO)C5H4Me ( 3 ) reacts with the disulfides S2R2 (R ? Ph, CH2Ph) by splitting of the sulfur-sulfur bond to form C5H5(PMe3)Co(SR)2 ( 4, 5 ). From 3 and S2Me2 a mixture of C5H5(PMe3)Co(SMe)2 ( 6 ) and [C5H5Co(μ-SMe)]2 ( 7 ) is obtained. The synthesis of C5H5(PMe3)Co(SCF3)2 ( 8 ) succeeds by treating 3 with N(SCF3)3. Whereas the reactions of 4 and 5 with MeI lead to the complex C5H5(PMe3)CoI2 ( 9 ), the dinuclear complex [C5H5(PMe3)Co(μ-SPh)]2(BF4)2 ( 11 ) is formed from 4 and [OMe3]BF4. The reactions of 11 with L = PMe3 and P(OMe)3 produce the compounds [C5H5Co(PMe3)(L)SPh]BF4 ( 12, 13 ), which react with [OMe3]BF4 to yield [C5H5Co(PMe3)(L)(MeSPh)](BF4)2 ( 14, 15 ). 相似文献
78.
Basic Metals. LXIV. Lewis-basic Bis(trimethylphosphine)cobalt Complexes with Indenyl and Trifluormethylcyclopentadienyl as Ligands The half-sandwich type compounds C9H7Co(PMe3)2 ( 1 ) and (C5H4CF3)Co(PMe3)2 ( 6 ) are prepared from CoCl(PMe3)3 and C9H7Li or TlC5H4CF3, respectively. They behave like metal bases and react with HBF4, CH3I (or CF3SO3CH3), I2, and CH3COCl by oxidative addition to give the cationic complexes [C9H7CoX(PMe3)2]+ and [(C5H4CF3)CoX(PMe3)2]+ (X ? H, CH3, I, COCH3) which are isolated as the PF6 salts ( 2–5 and 7–10 ). The 1HNMR and the IR spectra of the compounds 1–10 are discussed, also in comparison to those of the corresponding cyclopentadienylcobalt complexes. 相似文献
79.
Electrokinetic phenomena at grafted polyelectrolyte layers 总被引:1,自引:0,他引:1
During the last decades the electrokinetic theory of Smoluchowski (Z. Phys. Chem. 92 (1918) 129) was extended to be applicable for soft surfaces (grafted polyelectrolyte layers (PL), biological and artificial membranes, etc.) by either using the Debye approximation or numerical solutions. In the theory of Ohshima (Colloids Surf. A 103 (1995) 249) the nonlinearized Poisson-Boltzmann (PB) equation for thick and uniform PL is solved analytically and a general hydrodynamic equation is derived in an integral form. These advantages in the theory of Ohshima provided a base for the further development of a generalized electrokinetic theory for soft surfaces. In his theory the final equation for the electroosmotic (electrophoretic) velocity is specified for the case of the complete dissociation of ionic sites within PL. Accordingly, the equation may be used only if the difference between pK and pH is very large. However, it turned out that an analytical solution of the nonlinearized PB equation for thick PL is possible for any degree of dissociation. This was achieved using the approximation of excluded coions if the absolute value of the reduced Donnan potential is larger than 2 and due to the simplification in the case of weak dissociation, when the absolute value of the reduced Donnan potential is less than 2. Combining this generalized double layer (DL) theory for PL and the theory of Ohshima enables to obtain an analytical equation for electroosmosis for the general case of any degree of dissociation. This equation creates for the first time a theoretical base for the interpretation of electrokinetic fingerprinting (EF) for the characterization of soft surfaces. 相似文献
80.
Fries G Wolf J Ilg K Walfort B Stalke D Werner H 《Dalton transactions (Cambridge, England : 2003)》2004,(12):1873-1881
A series of unsymmetrical 1,2-bis(phosphino)ethanes R(2)PCH(2)CH(2)PR'(2) and 1-arsino-2-phosphinoethanes R(2)AsCH(2)CH(2)PR'(2) mainly with bulky substituents R and R' were prepared from the cyclic sulfate by stepwise cleavage of the carbon-oxygen bonds by LiPR(2) and LiPR'(2) or LiAsR(2) and LiPR'(2), respectively. Analogously, racemic mixtures of R(2)PCH(2)CH(Me)PPh(2)(R =iPr, Cy ) as well as the enantiomers (R)-, (R)- and (R)-tBu(2)PCH(2)CH(Me)PPh(2)(R)- were obtained from the corresponding unsymmetrical cyclic sulfates and (S)-. On a similar route, the racemates of the 1,3-bis(phosphino)propanes R(2)PCH(2)CH(2)CH(Me)PPh(2)(R =iPr, tBu ), optically pure (R)- and (S,S)-iPr(2)PCH(Me)CH(2)CH(Me)PPh(2)(S,S)- were prepared. The reaction of [[RhCl([small eta](4)-C(8)H(12))](2)] with chelating ligands L-L, where L-L is R(2)PCH(2)P(men)(2)(R =iPr, Ph; men =(1S,2R,5S)-menthyl), Cy(2)AsCH(2)P(men)(2), or (R)-, (R)-, (R)-, (R)- and (S,S)-, in the presence of AgPF(6), gave the complexes [Rh(eta(4)-C(8)H(12))(L-L)]PF(6) which were used as pre-catalysts in the hydrogenation of the methyl ester of alpha-acetamidocinnamic acid (ACM). Depending on L-L, the solvent, the temperature and the pressure of H(2), optical yields of up to 69% ee were achieved. For two of the rhodium complexes, and, the molecular structures were determined by X-ray crystallography. 相似文献