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111.
A new helically chiral hexacyclic system, bearing an acetoxymethyl group, was prepared from a simple naphthalene building block in good yield and purity, via a four-step sequence involving palladium-catalysed Heck couplings and oxidative photocyclizations. Suitable crystals of the latter indicate that its conformation closely resembles that of unsubstituted [6]helicene, whose idealized symmetry is C2. The optical properties of the hexacyclic helicene were investigated and show interesting behaviour. 相似文献
112.
Mouna Ferchichi Erwann JeanneauBernard Fenet Faouzi MeganemUlrich Darbost Isabelle Bonnamour 《Tetrahedron letters》2012,53(32):4047-4050
The synthesis of a series of six new per-substituted p-tert-butylcalix[9]arenes derivatives has been achieved. Functions such as ester, nitrile, or carbonate have been grafted on the phenolic oxygens of calix[9]arene: p-tert-butylcalix[9]arene nona-ethyl acetate, p-tert-butylcalix[9]arene nona-carboxylic acid, p-tert-butylcalix[9]arene nona-cyanopropyloxy, p-tert-butylcalix[9]arene nona-tert-butoxycarbonyle, p-tert-butylcalix[9]arene nona-acetyl, and p-tert-butylcalix[9]arene nona-trifluoroacetyl have been obtained in good yields (from 48% to 78%) and fully characterized. The X-ray structures of p-tert-butylcalix[9]arene nona-tert-butoxycarbonyl and p-tert-butylcalix[9]arene nona-ethyl acetate have been determined. A dynamic NMR study has revealed the high conformational mobility of such structures, even at low temperature. 相似文献
113.
Reduction in situ of WCl4(MeCN)2 with zinc in the presence of diazadiene ligands 1b-f is reported and produces a series of diamagnetic complexes (DAD)WCl22b-f. All complexes were characterized by 1H, 13C NMR and IR spectroscopic data. The crystal structures of complexes 2b and 2e were solved by X-ray diffraction methods. 相似文献
114.
Optical Review - Multimode fibers (MMF) are enjoying a renewed attention boosted by recent advances in multimode complex nonlinear optics. Reason behind nonlinearity is occurred either due to... 相似文献
115.
Faouzi Triki & Tao Yin 《计算数学(英文版)》2023,41(3):482-500
This paper concerns the reconstruction of a scalar coefficient of a second-order elliptic equation in divergence form posed on a bounded domain from internal data. This problem finds applications in multi-wave imaging, greedy methods to approximate parameter-dependent elliptic problems, and image treatment with partial differential equations. We first show that the inverse problem for smooth coefficients can be rewritten as a linear transport equation. Assuming that the coefficient is known near the boundary, we study the well-posedness of associated transport equation as well as its numerical resolution using discontinuous Galerkin method. We propose a regularized transport equation that allow us to derive rigorous convergence rates of the numerical method in terms of the order of the polynomial approximation as well as the regularization parameter. We finally provide numerical examples for the inversion assuming a lower regularity of the coefficient, and using synthetic data. 相似文献