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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and X-Ray Diffraction Analysis of Bis(phenylsulphonyl)semibullvalenes. Lifting of the Degeneracy of Semibullvalenes in the Crystal Lattice[1] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 955-968 
    Details
    ISSN: 0009-2940
    Keywords: Semibullvalenes ; [n.3.3] Propellanes, derivatives of ; Vinyl sulphides and sulphones ; Bromination, allylic ; Debromination ; Zinc-copper couple ; Cope rearrangement in the solid state ; Valence tautomers, non-equivalent ; Equilibrium constants from atomic distances ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bicyclo[3.3.0]octanediones 4 and 9a, b and the [n.3.3]-propellanediones 9c, d, f, h react with thiophenol in the presence of titanium(IV) chloride and triethylamine to afford high yields of the vinyl sulphides 5 and mixtures of the vinyl sulphides 10/11. Sodium perborate oxidizes the vinyl sulphides 5 and 10/11 to the corresponding vinyl sulphones 6 and 12/13. N-Bromosuccinimide converts 6 into the dibromodisulfones 7. The exo,exo configuration of 7b is established by X-ray crystallography. The mixtures of disulphones 12/13 are brominated by N-bromosuccinimide to yield complex mixtures of uncharacterized dibromodisulphones 14. Debromination of the dibromodisulphones 7, and the mixtures of 14 as well, by the zinc-copper couple results in the formation of crystalline semibullvalenes 8 and 15 in moderate to high yields. - X-ray diffraction analyses of 8a, b and 15a-d reveal large variations of the apparent atomic distances in the cyclopropane rings (C2-C8) and at the open ends of the molecules (C4…C6). This result is interpreted in terms of equilibrating, non-degenerate valence tautomers resulting in averaged atomic distances. The equilibrium constants are calculated from the atomic distances on the basis of a limiting value of 157.8 pm for the C2-C8 bonds of the non-rearranging valence tautomers. The results are compared to those obtained from X-ray diffraction analyses of other substituted semibullvalenes. The lifting of the degeneracy of semibullvalenes in the solid state is attributed to subtle intermolecular interactions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250430
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  • 2
    Electronic Resource
    Electronic Resource
    2,6-Dimethyl Semibullvalene-2,6-dicarboxylates (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2613-2623 
    Details
    ISSN: 0009-2940
    Keywords: Semibullvalene-2,6-dicarboxylates ; Decarbalkoxylation ; Reduction of β-oxo esters ; Vinyl sulphides and sulphones ; Esters, α,β-unsaturated, from nitriles ; Bicyclo[3.3.0]octa-2,6-diene-2,6-dicarboxylates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enolized β-oxo ester 9 is reduced by NaB(CN)H3 in weakly acidic methanol solution to afford an almost quantitative yield of a mixture of diastereomeric β-hydroxy esters 10. On treatment with phosphorus oxychloride in pyridine, 10 is converted into a mixture of the β-chloro esters exo-11, endo-11, exo-12, endo-12, and 13 which is separated in part by chromatography. Sodium methoxide in methanol eliminates hydrogen chloride from the crude mixture of β-chloro esters producing the α,β-unsaturated ester 7a in 84% yield based on 9. - Acid-catalysed equilibration of the known vinyl sulphides C2- and Cs-15 is carried out on large scale furnishing a 73:27 ratio of C2- and Cs-15. This mixture is oxidized to the sulphones C2- and Cs-16 which are allowed to react with sodium cyanide supported on aluminium oxide affording the α,β-unsaturated dinitrile 17 which is isolated by chromatography. Thus, 17 is now available on a 30-g scale. Methanolysis of 17 by a prolonged treatment with hydrogen chloride in methanol followed by hydrolysis of the Pinner salt leads to 7b. - Both α,β-unsaturated esters 7a and b are readily brominated at the allylic positions by N-bromosuccinimide to yield the γ,γ′-dibromo esters 19a and b. Zinc-copper couple in tetrahydrofuran converts 19a and b into the semibullvalenedicarboxylates 2a and b. While 2a is persistent only in dilute solutions, thus frustrating all attempts at its isolation, 2b exhibits considerable stability in solution and forms lemon-coloured crystals. The semibullvalenedicarboxylates 2a and b undergo a very rapid degenerate Cope rearrangement in solution. In addition, 2b exhibits reversible thermochromism in both solution and solid state. The structures of the new compounds are based on spectroscopic evidence, including mass, IR, and NMR spectra. The configurations of exo-11, exo-12, 19a and b are established by X-ray diffraction analyses.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251135
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  • 3
    Electronic Resource
    Electronic Resource
    Ring Expansion of Heterocyclic Ketene N,X-Acetals and 2-Alkylidenedihydroindoles with Methanesulphonyl Azide by [3 + 2] Cycloaddition and Subsequent Extrusion of Molecular Nitrogen (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1541-1549 
    Details
    ISSN: 0947-3440
    Keywords: [3 + 2] Cycloaddition ; Ketene N,X-acetals, cyclic ; Azides, electrophilic ; Amidines, cyclic N-sulphonyl- ; Ring expansion of heterocycles ; 1,2-Shift of carbon, nitrogen, sulphur, or selenium ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methanesulphonyl azide (2) reacts readily with isolated cyclic ketene N,X-acetals of type 1, viz. 10a, d, 15b, d, and 22a-c, or those that are generated in situ by deprotonation of the corresponding 2-alkylbenzazolium tetrafluoroborates, i.e. 14a → 15a, 14b → 15b, and 18 → 19. Ring-expanded products are formed by extrusion of molecular nitrogen from intermediate labile [3 + 2] cycloadducts 3 with concomitant 1,2-shift of N (route A1 → 12, 24) or X (route A2 → 16, 20, 21). In addition, 3 may undergo [3 + 2] cycloreversion into N-sulphonylimine 5 and diazoalkane 6 (route B → 13, 17, 25). The configurations of the cyclic N-sulphonylamidines 16b and 21b, the N-sulphonylimine 24 and the N-sulphonylamine 27 are elucidated by means of X-ray diffraction analyses. The ratio of the (useful) ring-expansion reactions vs. the unwanted formation of 5 + 6 is hardly influenced by the solvent employed and temperature of the experiment but strongly by the nature of the potential migrating atom and the substituents at the α-carbon atom.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961008
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  • 4
    Electronic Resource
    Electronic Resource
    [3.3.3]Propelladiendicarbonitrile (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 503-513 
    Details
    ISSN: 0170-2041
    Keywords: [3.3.3]Propellanecarbonitriles ; Tricyclo[3.3.3.01.5]undecane-3,7-dione ; NBS Bromination ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [3.3.3]Propelladienedicarbonitriles1)The 3,7-diketone 5 reacts with 4-chlorothiophenol in the presence of titanium tetrachloride/triethylamine to afford equal amounts of the vinyl sulfides C2/C5-6 in 95% yield. Equilibration of the 1:1 mixture of C2/C5-6 is catalyzed by trifluoroacetic acid and produces a 3:2 ratio of C2/C5-7 in almost quantitative yield. Potassium cyanide supported on aluminium oxide in boiling 2-methyl-2-butanol converts the latter into a mixture of the α,β-unsaturated dinitriles 1b, 11, 13, and 14, which are separated by chromatography. The intermediates 8 and 10 as well as the products 9 and 12 resulting from the addition of hydrogen cyanide to 1b and 11, respectively, are isolated in the same way. The dinitrile 1b is brominated by N-bromosuccinimide to afford a mixture of endo-15, exo-15, endo,endo-16, endo,exo-16, and 17, most of which are separated by chromatography. The endo-bromodinitrile endo-15 reacts with potassium methoxide in methanol to yield the exo-methoxydinitrile 18. The configuration of the dinitriles endo-15, endo,endo-16, and 18 is established by NOE difference spectroscopy and X-ray diffraction analyses.
    Notes: Das 3,7-Diketon 5 reagiert mit 4-Chlorthiophenol in Gegenwart von Titan(IV)-chlorid/Triethylamin zu gleichen Mengen der Bis(vinylsulfide) C2/C5-6 (65% Ausb.), die unter Trifluoressigsäure-Katalyse zu einem (3:2)-Gemisch äquilibriert werden. Oxidation von C2/C5-6 mit Natriumperborat-tetrahydrat in Essigsäure ergibt fast quantitativ die Bis(vinylsulfone) C2/C5-7. Diese liefern mit Kaliumcyanid auf Aluminiumoxid in siedendem 2-Methyl-2-butanol ein Gemisch der α,β-ungesättigten Dinitrile 1b, 11, 13 und 14, die chromatographisch getrennt werden So werden auch die Zwischenstufen 8 und 10 sowie Folgeprodukte von 1b und 11, nämlich die Trinitrile 9 und 12, isoliert. das Dinitril 1b wird mit N-Bromsuccinimed zu einem Gemisch von endo-15, exo-15, endo,endo-16, endo,exo-16 und 17 bromiert, das größtenteils chromatographisch getrennt wird. Das endo-Bromdinitril endo-15 reagiert mit Kaliummethanolat in Methanol zum exo-Methoxydinitril 18. Die Konfiguration der Dinitrile endo-15, endo,endo-16 und 18 wird durch NOE-Differenz-Spektren und Röntgenstrukturanalyse bewiesen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890190
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