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Christian Chapius Piotr Rzepecki Tomasz Bauer Janusz Jurczak 《Helvetica chimica acta》1995,78(1):145-150
Under the co-operative influence of two prosthetic groups, and independent of the TiCl4 concentration, complete and constant diastereofacial π-selection was achieved during the [4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroyl-di[(2R)-bornane-10,2-sultam] ((?)- 1c ); reactive conformations are discussed. 相似文献
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Tomasz Bauer Christian Chapuis Anna Kucharska Piotr Rzepecki Janusz Jurczak 《Helvetica chimica acta》1998,81(2):324-329
Among seventeen different Lewis acids, TiCl4 was found to be the best catalyst for the [4 + 2] cycloaddition of cyclopentadiene to N,N′-fumaroylbis[(2R)-bornane-10,2-sultam] ((?)- 1 ). Independently of the TiCl4 molar concentration, almost constant and complete (98–89% d.e.) diastereofacial π-selection was achieved in the Diels-Alder addition of (?)- 1 to cyclopentadiene, cyclohexadiene, isoprene, and 2,3-dimethylbuta-1,3-diene. 相似文献
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Michal Achmatowicz Christian Chapuis Piotr Rzepecki Janusz Jurczak 《Helvetica chimica acta》1999,82(2):182-190
The [4+2] cycloaddition of cyclopentadiene to the (2R)-bornane-10,2-sultam derivative (−)- 1b of fumaric monomethyl ester proceeds with high endo and π-facial diastereoselectivity in the presence of 0.5 mol-equiv. of TiCl4. The major diastereoisomer endo-(2R,3R)- 2b , isolated in 87% yield by crystallization, was subjected to X-ray crystal-structure analysis. Steric influence of ethyl- and benzyl-ester analogues (−)- 1c and (−)- 1d , respectively, is also reported. 相似文献
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The cyclic [2R,S(R)]‐bornane‐10,2‐sulfinamide (−)‐ 2b , an analogue of Oppolzer`s camphor‐derived sultam (−)‐ 2a , was synthesized by reduction of the known N‐alkylidenesulfinamide (+)‐ 1b with NaBH4. The uncatalyzed [4+2] cycloaddition of cyclopentadiene to the methyl ester (−)‐ 3b of the N‐fumaroylsulfinamide, obtained from (−)‐ 2b , proceeds with lower endo and π‐facial selectivity as compared to dienophiles (−)‐ 3a , c . In contrast to these latter, the diastereoselectivity is reversed either in apolar CCl4 or in the presence of TiCl4. This inversion is explained by a competitive C(α)‐si addition on the reactive anti‐s‐trans conformer. 相似文献
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Jürg K. Schneider Peter Hofstetter Ern Pretsch Daniel Ammann Wilhelm Simon 《Helvetica chimica acta》1980,63(1):217-224
N,N,N′,N′-Tetrabutyl-3,6-dioxaoctane-dithioamide, an Ionophore with Selectivity for Cd2+ The dioxa-dithioamide 3 behaves as a highly selective ionophore for Cd2+ in solvent polymeric membranes. It induces cation-permselectivity in these membranes with a transference number of 1 for Cd(NO3)2- and of 2 for CdCl2-solutions. In the presence of a proton carrier, 3 may be used to selectively pump Cd2+ through membranes by coupling with a pH gradient. 相似文献
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V. A. Al'bekov A. F. Benda A. F. Gontar' G. A. Sokol'skii I. L. Knunyants 《Russian Chemical Bulletin》1986,35(6):1305-1308
Conclusions Perfluoroazomethines react with cyclopentadiene at 160–180°C to form [2 + 4]-cycloadducts, viz., fluorine derivatives of 5-azabicyclo[2.2.1]hept-2-ene. These derivatives were used to obtain the products of the radical addition of chlorine, bromine, and bis(trifluoromethyl)-nitroxyl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1437–1440, June, 1986. 相似文献
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A Chiral N,N′‐Dioxide–ZnII Complex Catalyzes the Enantioselective [2+2] Cycloaddition of Alkynones with Cyclic Enol Silyl Ethers 下载免费PDF全文
Tengfei Kang Shulin Ge Dr. Lili Lin Yan Lu Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Angewandte Chemie (International ed. in English)》2016,55(18):5541-5544
A highly efficient enantioselective [2+2] cycloaddition between alkynones and cyclic enol silyl ethers was developed by using a chiral N,N′‐dioxide‐zinc(II) complex as a catalyst. This method functions well for a variety of terminal alkynes as well as cyclic enol silyl ethers, with good to excellent enantioselectivity (up to 97 % ee). This is also the first successful example for the catalytic enantioselective [2+2] cycloaddition of internal alkynes with cyclic enol silyl ethers to give fully substituted cyclobutenes. Meanwhile, the desired cyclobutene product can easily be transformed into fused cyclobutane derivatives. 相似文献
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CH2[N(SO2F)2]2 is monoclinic, space group P21/c, with 8 molecules in the unit cell. The structure, which was solved by direct methods in a straightforward manner and refined to R = 0.082 for 2647 diffractometer intensities, consists of discrete molecules. 相似文献
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Jaromír Marek Pavel Kopel Zdenk Trvní
ek 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):m558-m560
In the crystal structure of the title compound, [N,N′‐bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trithionato(2−)‐κ2N,S]zinc(II) ethanol solvate, [Zn(C8H22N4)2(C3HN3S3)]·C2H6O, the ZnII atom is octahedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐aminopropyl)ethylenediamine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a trithiocyanurate(2−) (ttcH2−) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds. 相似文献
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D. Hugh Powell Andr E. Merbach Gabriel Gonzlez Ern Brücher Kroly Micskei M. Francesca Ottaviani Klaus Khler Alex Von Zelewsky Oleg Ya. Grinberg Yakob S. Lebedev 《Helvetica chimica acta》1993,76(5):2129-2146
EPR Spectra have been measured for aqueous solutions of a series of Gd3+ complexes at variable temperature and a range of magnetic fields; S-band (0.14 T), X-band (0.34 T), Q-band (1.2 T), and 2-mm-band (5.0 T). The major contribution to the observed line widths is magnetic-field-dependent and is interpreted as being due to the modulation of the zero-field splitting produced by distortion of the complexes from perfect symmetry. The transverse and longitudinal relaxation matrices for an 8S ion with such an interaction have been calculated using Redfield theory with vector-coupling methods, and diagonalised numerically to obtain relaxation rates and intensities for the degenerate transitions which contribute to the multiplet. The observed line width, which is inversely proportional to the magnetic field at low temperatures, is best described by the intensity-weighted mean transverse relaxation time for the four transitions with non-zero intensity. A least-squares fit of the data yields the square of the zero-field splitting tensor, Δ2, and a correlation time, τv, with activation energy, Ev. The physical significance of these parameters and the extent of validity of the theoretical approach are considered. The parameters are used to predict the magnetic-field dependence of the longitudinal and transverse electronic relaxation times, which are discussed in the context of their relevance to 1H-NMR relaxivity. 相似文献
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The title compound (-)-N-[(3R)-3-cyclohexyl]-3-phenylpropananoyl]bornane-10,2sultam (C 25 H 35 NO 3 S,M r=429.60),a derivative of camphorsultam,crystallizes in the monoclinic space group P2 1 /c with a=10.3301(7),b=19.4040(13),c=11.8106(8),β=100.5580(10)°,V=2327.3(3) 3,Z=4,D c=1.226 g/cm 3,λ=0.71073,μ(MoKα)=0.165 mm-1 and F(000)=928.X-ray diffraction analysis reveals that the six-membered ring of sultam shows a boat form (Fig.1).The planes constructed by (C(4),C(5),C(6),C(7)) and (C(7),C(8),C(9),C(4)) form a dihedral angle of 69.5°.The C(1)-C(2)-C(3) plane forms dihedral angles to the aforementioned planes of 89.8(1) and 85.9(3)°,respectively.And molecules are linked via hydrogen bonding (C-H···N/O) interactions. 相似文献