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  • Medium-sized rings  (4)
  • Computational Chemistry and Molecular Modeling  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of 5,5,10,10-tetramethyl-1-oxacyclotridecane-6,7,8,9-tetrone - on the mechanism of the Rubottom reactionDedicated to Professor Hans-Dieter Scharf on the occasion of his 65th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1655-1661 
    Details
    ISSN: 0947-3440
    Keywords: Cyclic vicinal tetraketones ; Rubottom reaction ; Medium-sized rings ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 5,5,10,10-tetramethyl-1-oxacyclotridecan-6,7,8,9-tetrone (12) was achieved via a multistep procedure involving an oxidation known as the Rubottom reaction. The key intermediates were the dialdehyde (25), the diacid (33), the cyclic diketone (39) and the bis(silyl enol ether) (42). The oxidation of 42 with mCPBA yielded two diastereomers, the syn and anti bis(α-hydroxy ketones) (44, 45) the ratio of which depends strongly on the solvent used. This result combined with the isolation of the diepoxide (43) gives an insight into the stereochemistry of the Rubottom reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199509230
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and Structures of Cyclotetradeca-4,11-diynone, Cyclotetradeca-4,11-diyne-1,8-dione, Their Exomethylene Derivatives, and 1,8-Dioxacyclotetradeca-4,11-diyneDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1545-1550 
    Details
    ISSN: 0947-3440
    Keywords: Medium-sized rings ; Alkynes ; Conformation analysis ; Ketones ; Cyclizations ; Ether ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following 14-membered ring diynes have been synthesized: cyclotetradeca-4,11-diynone (4), cyclotetradeca-4,11-diyne-1,8-dione (6), the corresponding exomethylene derivatives 5 and 7, as well as 1,8-dioxacyclotetradeca-4,11-diyne (8). The synthesis of the diketal of 4 was achieved by the reaction of the ethylene ketal of 1,5-dibromopentan-3-one (9) with the dilithium salt of 1,8-nonadiyne. Similarly, the diketal of 6 was prepared from the dilithium salt of the ethylene ketal of 1,8-nonadiyn-5-one 11 with 9. The unprotected ketones 4 and 6 were obtained by treating the ketals 10 and 14, respectively, with HCl. The ketones 4 and 6 were transformed to the exomethylene derivatives by a Wittig reaction. The reaction of the dilithium salt of 5-oxanona-1,8-diyne (16a) with 1,5-dibromo-3-oxapentane (15) yielded 8. X-ray investigations of single crystals of 6 and 8 revealed chair conformations with a zig-zag arrangement, employing two anti orientations of the two chains between the triple bonds. A zig-zag arrangement of the chain containing the carbonyl group was also found in 4. In 3b and 7 Ci symmetry was found, with only one anti conformation in each chain. Molecule 6 crystallizes with C2h symmetry and 8 with a center of symmetry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970734
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  • 3
    Electronic Resource
    Electronic Resource
    Koopmans' defects in metal group VIII carbonyls - a many-body approachPart 16 in the series: “Electronic Structure of Organometallic Compounds.” Part 15: M. C. Böhm and R. Gleiter, J. Organomet. Chem., to appear. (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 3 (1982), S. 140-153 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The ionization potentials of iron pentacarbonyl (1), ethylene-iron tetracarbonyl (2), cobalt tetracarbonylhydride (3), and nickel tetracarbonyl (4) have been calculated using a Green's function perturbation method based on the INDO approximation. It is shown that the deviations from Koopmans' theorem are largest in the Co complex, while the smallest reorganization energies of strongly localized MOs with predominant metal 3d character are found in the Fe carbonyls 1 and 2. The calculated Koopmans' defects are analyzed by an investigation of the relaxation terms of the self-energy part and are compared with previous INDO results for Cr, Mn, and Fe tricarbonyl derivatives. Additionally, orbital energies, bond indices, and net charges for the ground states of 1-4 are calculated and compared with experimental data.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540030205
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  • 4
    Electronic Resource
    Electronic Resource
    Propella[34] prismane and its congeners: A MO-theoretical study (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 31-36 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometries of a fourfold bridged tricyclo[4.2.0.02,5]octa-3,7-diene (1) and its photoproducts 2 and 3 were calculated by Hartree-Fock ab initio (3-21G and DZP basis) and semiempirical (MNDO, AM1, MINDO /3) methods. It was found that due to the smaller distance between the double bonds in 1 (2.65 Å) as compared to the parent tricyclo[4.2.0.02,5]octa-3,7-diene (4) (2.91 Å), the sequence of the frontier orbitals is different. In the case of 1, the photochemical [2 + 2]cycloaddition is allowed, whereas in 4 it is forbidden. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540160104
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  • 5
    Electronic Resource
    Electronic Resource
    INDO-Type calculations on the ground state and various ionic states of transition metal tricarbonylsPart 10 in the series “Electronic Structure of Organometallic Compounds.” For Part 9, see ref. 1. (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 407-416 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: By means of the ΔSCF and transition operator (TO) methods based on a recently developed INDO extension to the first transition metal series, the first ionization potentials of benzene - chromium tricarbonyl (I), cyclopentadienyl manganese tricarbonyl (II), the iron - tricarbonyl complexes with trimethylenemethane (III), and cyclobutadiene (IV) have been calculated and compared with experimental data. It is shown that the electronic structure of I to IV can be rationalized by Hoffmann's fragment approach in both the ground state and the cationic hole states. Within the series I - IV there are remarkable energy differences in the ground state for MOs derived from the 1a1 and 1e orbitals of the M(CO)3 fragment. The observation that only one band is associated with the ionization events from MOs predominantly localized at the metal site is traced back to large relaxation effects. In the cationic hole states the split of the M(CO)3 fragment orbitals 1a1 and 1e is minute in all four compounds.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540010412
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular Structures of Cyclotetradeca-1,3,8,10-tetrayne and Cyclohexadeca-1,3,9,11-tetrayne (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2841-2843 
    Details
    ISSN: 1434-193X
    Keywords: Medium-sized rings ; Alkynes ; Structure elucidation ; X-ray diffraction ; Cyclic compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclotetradeca-1,3,8,10-tetrayne (3) and cyclohexadeca-1,3,9,11-tetrayne (4) have been prepared according to Sondheimer et al. The X-ray crystal structures of 3 and 4 reveal them to be in the chair conformation (3) and the twisted chair-chair-conformation (4). The tetrayne units in both molecules deviate considerably from linearity, giving rise to transannular distances of the terminal sp centers of 3.098(2) Å (3) and 4.147(2), 4.196(2) Å (4), and 3.390(2) Å (3) and 4.251(2), 4.252(2) Å (4) for the central sp atoms, respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation of 1-Azacyclododeca-3,8-diynes and 1,6-Diazacyclododeca-3,8-diynes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2113-2118 
    Details
    ISSN: 0947-3440
    Keywords: Medium-sized rings ; Cyclizations ; Alkynes ; Heterocycles ; Multicomponent reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of N,N′-dialkyl- and N,N′-diaryl-1,6-diazacyclodeca-3,8-diynes was achieved by reaction of alkyl- or arylamines with 1,4-dihalobut-2-yne under dilution conditions in yields of 5-15%. The compounds synthesized by this procedure were the N,N′-dimethyl (2b), N,N′-diethyl (2c), N,N′-diisopropyl (2d), N,N′-di-tert-butyl (2e), N,N′-dicyclohexyl (2f), N,N′-diphenyl (2g), and N,N′-di-p-tolyl (2h) derivatives. The parent compound 2a was obtained in ca. 40% yield by heating 2d with α-chloroethylchloroformate (20). Using 1,9-dibromonona-2,7-diyne (10) and methylamine or isopropylamine, respectively, the corresponding N-alkyl-1-azacyclodeca-3,8-diynes 4b and 4d were synthesized under dilution conditions. By heating 4d with 20 we obtained 1-azacyclodeca-3,8-diyne (4a). As side products of the cyclization reactions the trimers 18 and tetramers 12 and 19 were isolated and characterized. N-methyl-1-azacycloundeca-3,9-diyne (14b) was prepared by reaction of 1,10-dibromodeca-3,8-diyne (13) with methylamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971013
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