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  • Organic Chemistry  (6)
  • Solid-state structures  (2)
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1, 4, 5, 6-Tetrahydro-ν-tetrazin-DerivateThe title compounds 2 and 13 are readily available from α-lithiated N-alkyl-nitrosoamines 1 (see Tables 1 and 2) which decompose at - 73° to yield the N-oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations (la- 3- 4- 5- 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (-6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)-(5)] are reported.The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., 1H- (cf. Fig. 9) and 13C-NMR., PE. (Scheme 2), by an X-ray analysis of 2a (Fig. 4-8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4-atom-6-electron N—N=N≡N-system. Comparisons are made with 2-tetrazenes, the open chain analogues of 13, wherever possible. Raney-Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l-configuration through the 1H-NMR. spectra of the aminals 7 and 15. Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4].Compound 2a is dimerized to the bis (nitrosoamino)-2-tetrazene 18 by treatment with acid, ZnII, CuI or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20, with H2O2), or at the CH2-groups of the ring to give oxo-N-oxide 21 (with MnO2 or the ring contracted oxo-tetrazoline-N-oxide 22 (with KMnO4).Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N-methylimine, but no diazetidine 27. Silver and mercury complexes 29 are obtained from 13a, while Cr(CO)5. THF does not furnish a complex as with azocompounds, but rather replaces N2 in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 307-316 
    ISSN: 0009-2940
    Keywords: Halogen oxides ; Solid-state structures ; Intermolecular interactions ; Halogens ; Oxygen ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The development of new preparative and analytical techniques that allow appropriate handling and characterizations of the capricious halogen oxides have initiated a revival of their chemistry. Due to these recent activities, the amount of well-confirmed knowledge about such oxides has considerably increased. This is especially valid for the structural chemistry in the solid state, which (among other topics) has greatly benefitted from developments in the techniques of in situ crystal growth of low melting substances on a diffractometer. As a consequence, some general crystal chemical features have become apparent: The coordination polyhedra of the halogen oxides can be readily understood in terms of the qualitative VSEPR concept, and there is a pronounced tendency to form mixed valence compounds where the respective valence states can be easily deduced from the coordination polyhedra. Furthermore, intermolecular or interionic bonds are significant, with increasing importance when moving from chlorine to iodine. Finally, ClO2 appears to be the only representative with the halogen in an even oxidation state.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 447-457 
    ISSN: 0947-3440
    Keywords: Isoquino[1,2-b][3]benzazepines ; Iso-C-homoberbines ; Conformation analysis ; Bischler-Napieralski reaction ; Methyl ∊-hydroxycarboxylates ; Heterocycles ; Alkaloids ; Drug research ; Medicinal chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of Hexahydro-isoquino[1.2.-b][3]benzazepinesThe synthesis of the six hexahydro-isoquino[1,2-b][3]benzazepines 13a-f is described; their conformation is investigated by NMR spectroscopic methods, X-ray analysis and dehydrogenation with mercury(II) acetate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0947-3440
    Keywords: Isoquino[3,2-a][2]benzazepines ; B-Homoberbines ; Bischler-Napieralski reaction ; Calculations, MMX force-field ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of Hexahydro-isoquino[3,2-a][2]benzazepines of the B-Homoberbine TypeThe two-step synthesis of the hexahydro-isoquino[3,2-a][2]-benzazepines („B-homoberbines“) 4b-e is described. The main and some further products of the Bischler-Napieralski reaction of hydroxyamide 3c were isolated and identified. The conformation of the B-homoberbines was investigated by X-ray analysis, spectroscopic methods and dehydrogenation with mercury(II) acetate.
    Additional Material: 5 Tab.
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  • 5
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclopentenon-Derivate, X.  -  Ein einfacher Zugang zu Bicyclo[6.3.0]undecan-DerivatenEs wird ein einfacher Weg zu funktionalisierten Bicyclo[6.3.0]undecan-Derivaten beschrieben, die als Zwischenprodukte bei Terpensynthesen genutzt werden können. Die trans-Konfiguration des Acetals 12 wird durch eine Röntgenstrukturanalyse bewiesen.
    Notes: A straightforward route to functionalized bicyclo[6.3.0]undecane derivatives, which can be used in terpene synthesis, is described. The trans configuration of the acetal 12 is established by an X-ray structural analysis.
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0170-2041
    Keywords: CP-MAS NMR Spectroscopy ; Melanin ; Oxidative phenolic coupling ; Quinone methides ; Labelled compounds, 13C ; Dopamines ; Enzymes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-state NMR spectroscopy was applied to the analysis of melanins prepared by peroxidase-H2O2 oxidation of dopamines specifically 13C labelled in the α- or β-side chain positions. A surprisingly diverse pattern of signals indicated the presence of uncyclized dopamine and noradrenaline-derived units, in addition to indole and carbonyl carbon atoms. These structural features, coupled with the results obtained from elemental analysis of dopamine melanin samples prepared under different conditions, point to a pigment formation process more complex than previously believed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 1135-1142 
    ISSN: 0170-2041
    Keywords: Isoquino[2,1-b][2]benzazepines ; C-Homoberbines ; Bischler-Napieralski reaction ; Conformation studies of the homoberbines ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of the Hexahydro-isoquino[2,1-b][2]benzazepinesThe synthesis of Hexahydro-isoquino[2,1-b][2]benzazepines 6a-c in a three-step reaction is reported; their conformation is investigated by spectroscopic methods, X-ray analysis and dehydrogenation with mercury(II) acetate.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 35 (1996), S. 1286-1304 
    ISSN: 0570-0833
    Keywords: computer chemistry ; solid-state structures ; structure prediction ; synthesis planning ; Computer chemistry ; Solid-state reactions ; Solid-state structures ; Solid-phase synthesis ; Structure prediction ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is presented here that allows, in principle, the prediction of the existence and structure of (meta)stable solid compounds. It is based on a set of adjustable modules that are applied to the study of the energy function of the chemical system of interest. The main elements are a set of routines for global optimization and local minimization, as well as algorithms for the investigation of the phase space structure near local minima of the potential energy, and the analysis and characterization of the structure candidates. The current implementation focuses on ionic compounds, for which empirical potentials are used for the evaluation of the energy function in the first stage, and a Hartree-Fock algorithm for refinements. The global optimization is performed with a stochastic simulated annealing algorithm, and the local minimization employs stochastic quenches and gradient methods. The neighborhoods of the local minima are studied with the threshold algorithm. The results of this approach are illustrated with a number of examples: compounds of binary noble gases, and binary and ternary ionic compounds. These include several substances that have not been synthesized yet, but should stand a fair chance of being kinetically stable, for example further alkali metal nitrides besides Li3N, as well as Ca3SiBr2 or SrTi2O5.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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