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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and thermal isomerization of a cyclobuta[d]naphthalenone (1984)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 433-434 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00314a036
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  • 2
    Electronic Resource
    Electronic Resource
    Dual generation of the [4.4.4]propella-2,4,7,9,11-pentaenyl cation. Its threefold Wagner-Meerwein rearrangement cascade leading to 4a,7-dihydropleiadiene (1986)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 3739-3744 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00273a031
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  • 3
    Electronic Resource
    Electronic Resource
    Functionalized polyunsaturated [4.4.4]propellanes. Synthesis, intraring chemistry, and backbone rearrangements. [4.4.4]Propella-2,4,7,9,12-pentaene and its thermal frangibility (1986)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 3731-3739 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00273a030
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  • 4
    Electronic Resource
    Electronic Resource
    [4.4.4]Propella-2,4,7,9,12-pentaene. Synthesis and remarkable thermal stability (1984)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 1518-1519 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00317a075
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  • 5
    Electronic Resource
    Electronic Resource
    [4.4.4]Propellahexaene by triple Shapiro degradation. Structural and electronic properties of this maximally unsaturated hydrocarbon and consequences of O-methylation of its [4.4.4]propellatrienetrione precursors (1990)
    s.l. : American Chemical Society
    The @journal of organic chemistry 55 (1990), S. 1598-1611 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00292a040
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  • 6
    Electronic Resource
    Electronic Resource
    Vanadium(II)- and Niobium(III)-Induced, Diastereoselective Pinacol Coupling of Peptide Aldehydes to Give a C2-Symmetrical HIV Protease InhibitorDedicated to Professor Richard Neidlein on the occasion of his 65th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 307-315 
    Details
    ISSN: 0947-6539
    Keywords: enzyme inhibitors ; niobium complexes ; peptide aldehydes ; pinacol coupling ; vanadium complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Peptide aldehydes 15 a-c are prepared without epimerization from enantiomerically pure (S)-α-amino acids (Scheme 3). Reductive pinacol homocoupling of 15 a-c, induced by vanadium complex 11 or niobium complex 16 in refluxing THF, yields C2-symmetrical (S,R,R,S)-configurated 6a, 6b and 2, respectively, with moderate to high stereoselectivity (Scheme 4). In a novel protocol for the preparation and utilization of THF solutions of 11, the isolation of air-sensitive intermediates can be avoided and the potent HIV protease inhibitor 2 prepared in enantio- and diastereomerically pure form on a kilogram scale without chromatographic purification. The (S,R,R,S) selectivity of the pinacol homocouplings is confirmed by means of an independent, stereochemically unequivocal synthesis of 6 a and 2 from D-mannitol 4 (Scheme 1).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020312
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  • 7
    Electronic Resource
    Electronic Resource
    Reaktionen von trans-Cycloocten und von 7-Methoxy-1,3-dioxa-5(E)-cycloocten mit Allenen und mit Chlorsulfonylisocyanat. Bildung der ersten trans-anellierten Methylencyclobutane. Reaktion von Allen als En-Komponente (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2136-2164 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of trans-Cyclooctene and of 7-Methoxy-1,3-dioxa-5(E)-cyclooctene with Allenes and with Chlorosulfonyl Isocyanate., Synthesis of the First trans-Annulated Methylenecyclobutanes., Reaction of Allene as an Ene-Componenttrans-cyclooctene (1) exhibits [2 + 2]-cycloadditions with allene and with 1,1-dimethylallene in the temperature range 120-150°C, with methoxyallene at 90-100°C. The more strained 7-methoxy-1,3-dioxa-5(E)-cyclooctene (17) reacts at as much as 50°C lower temperature, even then suffering concurrently extensive dimerization. All the cycloadducts obtained are trans-annulated. Unsymmetrical allenes react preferentially at the more highly substituted double bond. Confronted with the enophilic trans-olefins 1 and 17, allene, but not 1,1-dimethylallene, behave as an enecomponent, besides the [2 + 2]-cycloaddition. In the cycloadducts of the unsymmetrical trans-olefine 17 the exocyclic double bond is Mainly turned away from the methoxy group. The reaction of trans-cyclooctene with 1,2-cyclononadiene at 90-100°C produces 1:2- and 2:2-cycloadducts (64, 65). At 0°C chlorosulfonyl isocyanate cycloadds to trans-cyclooctene utilizing its C=N bond (→46).
    Notes: trans-Cycloocten (1) geht [2 + 2]-Cycloadditionen mit Allen und mit 1,1-Dimethylallen im Temperaturbereich von 120-150°C, mit Methoxyallen bei 90-110°C ein. Das gespanntere 7-Methoxy-1,3-dioxa-5(E)-cycloocten (17) reagiert bereits bei um 50°C niedrigerer Temperatur, auch dann noch unter umfangreicher Dimerisierung von 17 als Konkurrenzreaktion. Alle Cycloaddukte sind trans-verknüpft. Die höher substituierte Doppelbindung unsymmetrischer Allene reagiert bevorzugt. Neben der [2 + 2]-Cycloaddition wirkt Allen, nicht aber 1,1-Dimethylallen, als En-Komponente gegenüber den enophilen trans-Cycloolefinen 1 und 17. Bei den Umsetzungen des unsymmetrischen Olefins 17 ist die exocyclische Doppelbindung der [2 + 2]-Cycloaddukte bevorzugt der Methoxygruppe abgewandt. Die Umsetzung von trans-Cycloocten mit 1,2-Cyclononadien bei 90-100°C liefert 1:2- und 2:2-Cycloaddukte (64, 65). Chlorsulfonylisocyanat reagiert mit trans-Cycloocten bei 0°C unter Cycloaddition an der C=N-Doppelbindung (→46).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160609
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  • 8
    Electronic Resource
    Electronic Resource
    Desaminierungsreaktionen, 33. Reaktionen aliphatischer Diazonium-Ionen mit Lithiumazid (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 2120-2144 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Deamination Reactions, 33. Reactions of Aliphatic Diazonium Ions with Lithium AzideThe reactions of aliphatic diazonium ions with lithium azide in methanol to give organic azides proceed by a variety of mechanisms. Azo coupling has been definitely established by means of 15N labels in the case of cyclopropane and alkenediazonium ions. The contribution of a pentazole to the coupling pathway is ca. 40% with cyclopropanediazonium ions, but less than 20% with alkenediazonium ions, as shown by a comparison of α- and β- 15N labeled diazonium ions. No coupling occurs with diazonium groups at sp3 hybridized carbons, including bicyclo[2.2.1]heptane-1-diazonium ions (2). Most of them produce alkyl azides by SN1 mechanisms; selectivities indicate some participation of azide ion in the extrusion of nitrogen from primary alkanediazonium ions. Whenever the diazo compounds generated by deprotonation of the diazonium ions are thermally labile, the carbenes thus produced also contribute to the formation of organic azides. Variations in product distribution, 15N content, and deuterium incorporation served to identify this novel mechanism.
    Notes: Die Reaktionen aliphatischer Diazonium-Ionen mit Lithiumazid in Methanol zu organischen Aziden verlaufen nach unterschiedlichen Mechanismen. Für Cyclopropan- und Alkendiazonium-Ionen wurde Azokupplung mit Hilfe von 15N-Markierung eindeutig nachgewiesen. Der Pentazol-Anteil an der Kupplungsreaktion beträgt ca. 40% bei Cyclopropandiazonium-Ionen, dagegen ≤ 20% bei Alkendiazonium-Ionen, wie aus dem Vergleich α- und β-15N-markierter Diazonium-Ionen hervorgeht. Diazoniumgruppen an sp3-hybridisiertem Kohlenstoff zeigen keine Kupplung, auch nicht Bicyclo[2.2.1]heptan-1-diazonium-Ionen (2). Aus ihnen entstehen Alkylazide meist nach einem SN1-Mechanismus; Selektivitätsuntersuchungen weisen auf die Beteiligung des Azid-Ions an der Stickstoffabspaltung aus primären Alkandiazonium-Ionen hin. Wenn die Deprotonierung der Diazonium-Ionen zu thermisch labilen Diazoverbindungen führt, tragen die so erzeugten Carbene ebenfalls zur Bildung organischer Azide bei. Veränderungen in der Produkt-verteilung, im 15N-Gehalt und im Deuterium-Einbau dienten zum Nachweis dieses neuartigen Mechanismus.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120621
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  • 9
    Electronic Resource
    Electronic Resource
    Desaminierungsreaktionen, 29: Zerfall von Bicyclo[4.1.0]heptan-7-diazonium-Ionen (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 1857-1872 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Demination Reactions, 29: Decomposition of Bicyclo[4.1.0]heptane-7-diazonium Ionsexo- (41) and endo-bicyclo[4.1.0]heptane-7-diazonium ions (42) have been generated by nitrous acid diazotization of the corresponding amines (21, 29) in the presence of sodium bromide. 41 afforded predominantly 7-exo-bromobicyclo[4.1.0]heptane (43) while 42 gave 2-cyclohepten-1-ol (44) arising from the hydrolysis of 3-bromocycloheptene (48). When the diazonium ions 41 and 42 were generated from the corresponding nitrosoureas (10 and 31) in weakly alkaline methanol, 7-exo-methoxybicyclo[4.1.0]heptane (50) and 3-methoxycycloheptene (51) were formed in the same ratio from both precursors. However, 42 reacted in CH3OD with complete exchange of 7-H for deuterium, indicating endo → exo isomerization. The cis-cycloheptene 51 was shown to arise by way of the trans isomer 55 by trapping the latter with furan. The configuration at C-3 of the furan adducts (59 and 60) suggests that both 50 and 55 originate from a partially opened cyclopropyl cation 56, in accord with a synchronous disrotatory reaction. Under strongly alkaline conditions the carbene 66 appears to contribute to the formation of 50.
    Notes: exo- (41) und endo-Bicyclo[4.1.0]heptan-7-diazonium-Ionen (42) wurden durch Diazotierung der entsprechenden Amine (21, 29) mit salpetriger Säure in Gegenwart von Natriumbromid erzeugt. 41 gab überwiegend 7-exo-Brombicyclo[4.1.0]heptan (43), während 42 2-Cyclohepten-l-ol (44), durch Hydrolyse von 3-Bromcyclohepten (48), lieferte. Wenn die Diazonium-Ionen 41 und 42 aus den entsprechenden Nitrosoharnstoffen (10 und 31) in schwach alkalischem Methanol erzeugt wurden, entstanden 7-exo-Methoxybicyclo[4.1.0]heptan (50) und 3-Methoxycyclohepten (51) aus beiden Vorstufen im gleichen Verhältnis. 42 reagierte jedoch in CH3OD unter vollständigem Austausch des 7-H durch Deuterium, d. h. unter endo → exo-Isomerisierung. Das cis-Cyclohepten 51 entsteht auf dem Weg über das trans-Isomere 55, wie durch Abfangen des letzteren mit Furan gezeigt wurde. Die Konfiguration an C-3 der Furan-Addukte (59 und 60) weist darauf hin, daß 50 und 55 aus einem „halbgeöffneten“ Cyclopropyl-Kation 56 hervorgehen, im Einklang mit einer synchronen, disrotatorischen Ringöffnung. Unter stark alkalischen Bedingungen scheint das Carben 66 zur Bildung von 50 beizutragen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110520
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  • 10
    Electronic Resource
    Electronic Resource
    Desaminierung von N-(2-Oxabicyclo[4.1.0]hept-7-exo-yl)-N-nitrosoharnstoff. Versuchte Erzeugung eines heterocyclischen trans-Cyclohepten-Derivats (1980)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 3570-3584 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Deamination of N-(2-Oxabicyclo[4.1.0]hept-7-exo-yl)-N-nitrosourea. Attempted Generation of a Heterocyclic trans-Cycloheptene DerivativeAlmost independently from the methoxide concentration the deamination of N-(2-oxabicyclo-[4.1.0]hept-7-exo-yl)-N-nitrosourea (11) in methanol produced nine mono- and dimethoxy compounds, eight of which could be identified (24-31). After deamination of 11 in methan-[D]ol the four main products had similar magnitudes of mono- and dideuteration. The position of the label was determined. Formation of the products does not occur by opening of the inner cyclopropane bond C-1/C-6, as in corresponding isocyclic systems, but by opening of the outer cyclopropane bond C-1/C-7.
    Notes: Die Desaminierung von N-(2-Oxabicyclo[4.1.0]hept-7-exo-yl)-N-nitrosoharnstoff (11) in Methanol liefert weitgehend unabhängig von der Methanolat-Konzentration neun Mono- und Dimethoxyverbindungen, von denen acht (24-31) identifiziert werden konnten. Nach Durchführung der Desaminierung in Methan-[D]ol konnte bei den vier Hauptprodukten ein ähnlicher Umfang an Mono- und Dideuterierung festgestellt und die Position der Markierung bestimmt werden. Die Produktbildung erfolgt nicht, wie bei entsprechenden isocyclischen Systemen, durch Öffnung der inneren Cyclopropanbindung C-1/C-6, sondern unter Öffnung der äußeren Cyclopropanbindung C-1/C-7.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19801131115
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