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31.
Fulvene-Dieters: Synthesis, Structure Elucidation and Thermal Behaviour In contrast to earlier assumptions, thermal reaction of pure fulvene ( 1a ), 6-methylfulvene ( lb ) and 6, 6-dimethylfuivene ( 1c ) at 227deg; gives oligomeric mixtures consisting mainly of the endo-[4 + 2]-eycloaddition products 2a , 2b and 2c . Thermal reactivity of the fulvenes decreases strongly in the series 1a > 1b > 1c . While the dimers 2b and 2c equilibrate very easily in solution above room temperature with 1b and 1c , respectively, 2a equilibrates with the isomer 5a (? 1, 6-Dimethyliden3a α, 3bβ, 6a α, 6bβ-tetrahydro-1-H), 6 H-bi (cyclopentadienylen). This surprising rearrangement envolves a formal 1,3-shift of the 1, 2-dihydrofulvene-unit of 2a (s. Scheme 4). 相似文献
32.
Hans-Peter Ros Rolf Kyburz Nigel W. Preston Rex T. Gallagher I. Ralph C. Bick Manfred Hesse 《Helvetica chimica acta》1979,62(2):481-487
The revised structure 1 is put forward for peduncularine, the main alkaloid of Aristotelia peduncularis (Labill.) HOOK. F. (Elaeocarpaceae), on the basis of its spectroscopic properties and those of its degradation products, the Hofmann base 3 and the hydrogenation product 4 . Structure 1 represents the relative configuration of the alkaloid. Peduncularine belongs to the class of indole alkaloids with a monoterpene unit as the aliphatic portion. To our knowledge it constitutes the first example in which an isopropyl group has become detached from the terpene unit and occurs as a substituent on nitrogen. 相似文献
33.
Hans-Peter Schröcker 《Central European Journal of Mathematics》2012,10(2):426-439
We study discrete conjugate nets whose Laplace sequence is of period four. Corresponding points of opposite nets in this cyclic
sequence have equal osculating planes in different net directions, that is, they correspond in an asymptotic transformation.
We show that this implies that the connecting lines of corresponding points form a discrete W-congruence. We derive some properties
of discrete Laplace cycles of period four and describe two explicit methods for their construction. 相似文献
34.
Markus Follmann Nils Griebenow Michael G. Hahn Ingo Hartung Franz‐Josef Mais Joachim Mittendorf Martina Schfer Hartmut Schirok Johannes‐Peter Stasch Friederike Stoll Alexander Straub Peter Jeschke Ralf Nauen Michael Edmund Beck Hans‐Wilhelm Engels Hans‐Georg Pirkl Reinhard Albers Rolf W. Albach Jens Krause Andreas Hoffmann Holger Casselmann Jeff Dormish 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(36):9503-9503
35.
Ferenc Hartung 《Annali di Matematica Pura ed Applicata》2013,192(1):17-47
In this paper, we consider a class of nonlinear neutral differential equations with state-dependent delays in both the neutral and the retarded terms. We study well-posedness and continuous dependence issues and differentiability of the parameter map with respect to the initial function and other possibly infinite dimensional parameters in a pointwise sense and also in the C-norm. 相似文献
36.
Oliver Brücher Uwe Bergsträßer Harald Kelm Jens Hartung Marco Greb Ingrid Svoboda Hartmut Fuess 《Tetrahedron》2012,68(34):6968-6980
A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion. 相似文献
37.
Christian Reichardt Hans-Peter Erfurt Klaus Harms 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):1081-1092
Attempts at the oxidation of 3-ethyl-2-methylbenzothiazolium salt 2 with a variety of oxidizing reagents did not lead to the desired isochiral S -oxide 3 or achiral S , S -dioxide 4 , in some cases, however, unexpectedly to the ring-opened dimeric 2,2'-di( N -ethyl-acetamino)substituted diphenyl disulfane 5 , the molecular structure of which was confirmed by x-ray analysis. The synthesis of 2-methylbenzothiazole- S , S -dioxide 14 , reported by Zincke et al. in 1915, turned out to be not reproducible. \centerline{\epsfbox{:art:fig-01.jpg}} 相似文献
38.
Dr. Claudia Kolbeck Dr. Alexey Deyko Dr. Takashi Matsuda Florian T. U. Kohler Prof. Dr. Peter Wasserscheid Dr. Florian Maier Prof. Dr. Hans-Peter Steinrück 《Chemphyschem》2013,14(16):3726-3730
We present the first systematic study of the influence of temperature on the degree of surface enrichment of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs). Using angle-resolved X-ray photoelectron spectroscopy, we demonstrate that the degree of surface enrichment strongly decreases with increasing temperature for all the studied ILs. For ILs with the same cation, but different anions, [C8C1Im]Br, [C8C1Im][TfO] and [C8C1Im][Tf2N], no significant differences of the temperature-induced partial loss of surface enrichment are found. Measurements for [C4C1Im][TfO], [C8C1Im][TfO] and [C18C1Im][TfO] indicate a small effect of the chain length. For [C18C1Im][TfO], a continuous decrease of alkyl surface enrichment is found with increasing temperature, with no abrupt changes at the phase-transition temperature from the smectic A to the isotropic phase, indicating that the surface enrichment is not affected by this phase transition. 相似文献
39.
Carbon‐Coated LiTi2(PO4)3: An Ideal Insertion Host for Lithium‐Ion and Sodium‐Ion Batteries 下载免费PDF全文
Dr. Vanchiappan Aravindan Dr. Wong Chui Ling Steffen Hartung Nicolas Bucher Prof. Srinivasan Madhavi 《化学:亚洲杂志》2014,9(3):878-882
We report the extraordinary performance of carbon‐coated sodium super ion conductor (NASICON)‐type LiTi2(PO4)3 as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON‐type compound was prepared by means of a Pechini‐type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field‐emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two‐phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon‐coated NASICON‐type LiTi2(PO4)3 hosts attractive for the development of next‐generation batteries. 相似文献
40.
Daniel Wechsler Cynthia Carolina Fernndez Julia Kbl Lisa-Marie Augustin Corinna Stumm Norbert Jux Hans-Peter Steinrück Federico Jos Williams Ole Lytken 《Molecules (Basel, Switzerland)》2021,26(10)
Porphyrins are large organic molecules that are interesting for different applications, such as photovoltaic cells, gas sensors, or in catalysis. For many of these applications, the interactions between adsorbed molecules and surfaces play a crucial role. Studies of porphyrins on surfaces typically fall into one of two groups: (1) evaporation onto well-defined single-crystal surfaces under well-controlled ultrahigh vacuum conditions or (2) more application-oriented wet chemical deposition onto less well-defined high surface area surfaces under ambient conditions. In this study, we will investigate the wet chemical deposition of 5-(monocarboxyphenyl)-10,15,20-triphenylporphyrin (MCTPP) on well-defined rutile TiO2(110) single crystals under ambient conditions. Prior to deposition, the TiO2(110) crystals were also cleaned wet-chemically under ambient conditions, meaning none of the preparation steps were done in ultrahigh vacuum. However, after each preparation step, the surfaces were characterized in ultrahigh vacuum with X-ray photoelectron spectroscopy (XPS) and the result was compared with porphyrin layers prepared in ultrahigh vacuum (UHV) by evaporation. The differences of both preparations when exposed to zinc ion solutions will also be discussed. 相似文献