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51.
Preliminary results leading towards the total synthesis of Brefeldin A are presented. 相似文献
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γ-Lactone-cis-annulation to Δ2- and Δ3- Cholestene. From Δ2- and Δ3- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The 13C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported. 相似文献
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Hanns‐Dieter Amberger Lixin Zhang Hauke Reddmann Christos Apostolidis Olaf Walter 《无机化学与普通化学杂志》2006,632(15):2467-2470
Electronic Structures of Organometallic Compounds of f Elements. 64 Does the Zwitterionic Nature of the Triphenylphosphine Oxide Ligand Manifest itself in its Spectrochemical Properties? The triphenylphosphine oxide mono adducts of the moiety tris(η5‐cyclopentadienyl)lanthanide(III) (Ln(Cp)3; Ln = Pr ( 1 ), La ( 2 )) were synthesized and structurally characterized. The Ln–O distances of these compounds are noticeably shorter than those of the corresponding THF adducts. A crystal field (CF) analysis of the optical spectra of 1 leads to a low absolute value of the quadratic CF parameter which is comparable with those of [Pr(Cp)3(L)]? adducts with anionic bases but not with [Pr(Cp)3(MeTHF)]. Reasons for the latter finding are presented. 相似文献
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The percolation transition of geometric clusters in the three-dimensional, simple cubic, nearest neighbor Ising lattice gas model is investigated in the temperature and concentration region inside the coexistence curve. We consider quenching experiments, where the system starts from an initially completely random configuration (corresponding to equilibrium at infinite temperature), letting the system evolve at the considered temperature according to the Kawasaki spinexchange dynamics. Analyzing the distributionn
l(t) of clusters of sizel at timet, we find that after a time of the order of about 100 Monte Carlo steps per site a percolation transition occurs at a concentration distinctly lower than the percolation concentration of the initial random state. This dynamic percolation transition is analyzed with finite-size scaling methods. While at zero temperature, where the system settles down at a frozen-in cluster distribution and further phase separation stops, the critical exponents associated with this percolation transition are consistent with the universality class of random percolation, the critical behavior of the transient time-dependent percolation occurring at nonzero temperature possibly belongs to a different, new universality class. 相似文献
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Thomas M. Klapötke Burkhard Krumm Dieter Naumann 《Journal of fluorine chemistry》2004,125(6):997-1005
The perfluoroaryl tellurolates C6F5TeLi (1) and 4-CF3C6F4TeLi (2) were prepared. These intermediates were identified by NMR spectroscopy and may form, depending on the reaction conditions, either the corresponding ditellanes C6F5TeTeC6F5 (3) and CF3C6F4TeTeC6F4CF3 (4) by subsequent oxidation, or in the case of 1, a telluranthrene (C6F4Te)2 (5) by reaction with itself. The halogenation products of 5, ( C6F4Te)2F4 (6), (C6F4Te)2Cl4 (7), (C6F4Te)2Br4 (8), as well as the azidation product (C6F4Te)2(N3)4 (9) were synthesized. Furthermore, in pursuit of our recent work on tellurium azides, the syntheses and properties of R2Te(N3)2 (R=CF3 (10), C6F2H3 (11)) and RTe(N3)3 (R=CF3 (12) and C6F5 (13)) are reported. The crystal structures of CF3C6F4TeTeC6F4CF3 (4), (C6F4Te)2Br4 (8), and (C6F2H3)2Te(N3)2 (11) were determined. 相似文献