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  • 1985-1989  (37)
  • 1970-1974  (16)
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  • 1
    Digitale Medien
    Digitale Medien
    Synthese substituierter Cyclononatetraene42. Mitt. über Fulvene, Fulvalene. 41. Mitt.: [1]. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 623-634 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Substituted CyclononatetraenesIn the course of an exploration of possible synthetic pathways to nonafulvenes, a series of 1-substituted cyclononatetraenes (CNT) 4b-1 have been prepared in yields of about 60%. Their structures follow from spectroscopic data as well as from the quantitative valence isomerisation to 1-endo-substituted cis-3a, 7a-dihydroindenes 8. Both all-cis-CNT- 1 and cis,cis,cis,trans-CNT- 2 have been used as nucleophiles. Whereas 2 is normally more nucleophilic than 1, the yield of cyclononatetraenes 4 prepared with 2 may be reduced due to by-products such as 9 and 10.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680315
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  • 2
    Digitale Medien
    Digitale Medien
    Synthese neuer Nonafulvene44. Mitt. über Fulvene, Fulvalene, 43. Mitt. [1]; Kurzmitteilungen [2] [3]. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1543-1556 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of New NonafulvenesNonafulvenes 1c and 1m-s are prepared by the following methods: (a) Elimination of AcOH from acetoxyalkyl-cyclononatetraenes (Scheme 2; 1m); (b) alkylation of nonafulvenolates (Scheme 3; 1c, 1n); (c) elimination of alcohol from di- and trialkoxymethyl-cyclononatetraenes (Scheme 5; 1o, 1p, 1q); (d) deprotonation of intermediary formed formamidiniumcyclononatetraenes (Scheme 6; 1r, 1s). Scope and limitations of these preparative sequences are discussed and compared with the corresponding pentafulvene syntheses.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680606
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  • 3
    Digitale Medien
    Digitale Medien
    Synthese und NMR-Spektren von Nonafulven sowie Vergleich mit 10-PhenylnonafulvenHerrn Prof. Dr. Hans Nitschmann zum 80. Geburtstag gewidmet52. Mitt. über Fulvene, Fulvalene; 51. Mitt. [1]; Kurzmitt. [2]. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 862-880 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and NMR Spectra of Nonafulvene and Comparison with 10-PhenylnonafulveneExperimental procedures for the reaction of cis,cis,cis,trans-cyclononatetraenide (ccct-CNT-; see 4) with bromomethyl acetate (1a, R = H, X = Br) to give (cyclononatetraenyl)methyl acetate (5a; 84% yield) as well as for the base-induced elimination of HOAc from 5a to give nonafulvene (6a; 44% yield) are described. Spectroscopic as well as chemical evidence for 6a and 6b is presented. An approximate high-field-NMR analysis of 6a and 6b has been completed. The results are in favour of a fast interconversion of the type 6A⇄6B (Scheme 4), and supported by the MNDO-optimised geometry of 6a. The first X-ray analysis of a cyclononatetraene (i.e. of 5b) has been accomplished: 5b is a polyolefinic molecule with largely alternating bond lengths and with a nine-membered ring deviating strongly from planarity.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19870700327
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  • 4
    Digitale Medien
    Digitale Medien
    Synthese von Triafulven-Vorstufen aus trisubstituierten Cyclopropanen54. Mitt. über Fulvene, Fulvalene, 53. Mitt.: [1]. Kurzmitt.: [2] [3]. (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 2026-2033 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Triafulvene-Precursors from Trisubstituted CyclopropanesTrisubstituted cyclopropanes 5a-f are prepared by carbene addition to the appropriate olefins. While 5a (Y = OAc) and 5c (Y = Cl) rearrange in the presence of BuLi, 5d (Y = SPh) is stable enough to allow the envisaged sequence for triafulvene (Scheme 2) : halogen-Li exchange, followed by methylation of 6d, gives 7d in a 93% yield; after base-induced elimination of HBr from 7d, the key precursor 1-methylene-2-(phenylthio)cyclopropane (9, 70% yield) is isolated. Compound 9 is transformed into the corresponding sulfoxide 10 (83%), sulfone 11 (80%), and sulfonium fluoroborate 12 (95% yield) by subsequent oxidation and methylation, respectively. Some 1H-NMR results of cyclopropanes 5a-f and 7d as well as of methylidene-cyclopropanes 9-11 are discussed.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19880710820
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  • 5
    Digitale Medien
    Digitale Medien
    Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 29-40 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19890720105
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  • 6
    Digitale Medien
    Digitale Medien
    Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 41-50 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19890720106
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  • 7
    Digitale Medien
    Digitale Medien
    Bis (2,4,6,8-cyclononatetraen-1-yl)methane43. Mitt. über Fulvene und Fulvalene. 42. Mitt.: [1]. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 887-891 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Bis (2,4,6,8-cyclononatetraen-1-yl)methanesBis (2,4,6,8-cyclononatetraen-1-yl)methanes (2a-c) have been prepared by reaction of all-cis-cyclononatetraenide with 1,1-dichlorodimethyl ether as well as with carbenium ion precursors 9b and 9c. The title compounds 2 are attractive precursors of highly delocalised nonafulvenes of type 3; however, elimination experiments 2→3 failed so far.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19850680409
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  • 8
    Digitale Medien
    Digitale Medien
    Synthese von Triafulven-Vorstufen für Retro-Diels-Alder-Reaktionen48. Mitt. über Fulvene, Fulvalene, 47. Mitt.: [1]. (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 835-848 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Triafulvene Precursors for Retro-Diels-Alder ReactionsTriafulvene precursors exo-15 and endo-15 have been prepared by addition of dibromocarbene to benzobarrelene 12 followed by a lithium-halogen exchange, methylation, and elimination of HBr (12→13→14→15), (Scheme 2). Gas-phase pyrolysis of exo/endo-mixtures of 15 above 400° gave minor amounts of naphthalene (16), traces of a hydrocarbon C4H4 identified by MS (presumably triafulvene 1) and predominantly (36%) the isomerization product 17 (Scheme 3). In a second synthetic approach the well-known cycloheptatriene-norcaradiene equilibrium of type 26⇆27 has been utilised to prepare various endo-trans-3-(X-methyl) tricyclo[3.2.2.02,4]nona-6,8-dienes 31 (Scheme 5). However, numerous elimination experiments 31→9 failed so far. The structure of two rearrangement products 33 and 34 (Scheme 6) has been elucidated.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19860690410
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  • 9
    Digitale Medien
    Digitale Medien
    Synthese von Pentafulvalen durch oxidative Kupplung von Cyclopentadienid mittels Kupfer(II)-chlorid50. Mitteilung über Fulvene, Fulvalene; 49. Mitteilung: [1]; Kurzmitteilung: [2]. (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 1644-1654 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Pentafulvalene by Oxidative Coupling of Cyclopentadienide with Copper(II) ChlorideStarting with a nearly quantitative coupling of cyclononatetraenide 7 to 1, 1′-dihydrononafulvalene 8 by means of AgBF4, a simple general synthetic concept for fulvalenes is outlined (Scheme 2), consisting in an oxidative coupling of ‘Hückel anions’ like 2 and 7 to 1, 1′-dihydrofulvalenes 10 with Ag(I) or Cu(II) salts, followed by deprotonation (→11) and oxidation (→12); it has been realised in the case of pentafulvalene (1; overall yield 61%; Scheme 3) and 1,2:5,6-dibenzopentafulvalene (18; overall yield 66%, Scheme 4). NMR-spectroscopic investigations show that 1 is a non-aromatic compound with strongly alternating bond-lengths, its π-system being even more localised than that of simple pentafulvenes. In fact, 1 is extremely reactive in concentrated solutions above -50°. Besides of polymerisations, Diels-Alder dimerisation 1→19 followed by a rearrangement 19→20 takes place (Scheme 5).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19860690719
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  • 10
    Digitale Medien
    Digitale Medien
    Nonapentafulvalen51. Mitteilung über Fulvene, Fulvalene; 50. Mitteilung: [1]; Kurzmitteilung: [2].Teil der Dissertation von A.E. [3]. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 49-58 
    Details
    ISSN: 0018-019X
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Nonapentafulvalene(1) has been prepared by oxidative coupling of sodium cyclopentadienide (6) and sodium cyclononatetraenide (7) with CuCl2 in THF, two-fold deprotonation of cyclopentadienyl-cyclononatetraene 8 to give dianion 16, and oxidative treatment of 16 with CuCl2 (Schemes 2 and 3). Compound 1 is a highly reactive and thermally instable molecule, since valence isomerisation 1 → 17 proceeds easily even at low temperature (the half-life of 1 is ca. 30 min at -15° in CDCl3). NMR investigations show that nonapentafulvalene is an olefinic molecule with strongly alternating bond lengths, its nine-membered ring deviating strongly from planarity. Comparison of the NMR data of 1 with those of a series of sterically similar pentafulvenes 18 and nonafulvenes 19 (Tables 1 and 2) demonstrates that (a) with regard to the pentafulvene unit of 1, the cyclononatetraene ring acts as very weak electron-donating group, while (b) with regard to the nonafulvene unit of 1, the cyclopentadiene ring acts as weak electron-accepting group. So nonapentafulvalene may be regarded as a ‘nonafulvene of inverse π-polarisation’.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/hlca.19870700106
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