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  • 1
    Electronic Resource
    Electronic Resource
    Heterocyclic ring-closure reactions. 8. Reactions of isothiocyanates with cyanothioformamides. Cyclization of 5-imino-4-thioxo-2-imidazolidones and 5-imino-2,4-imidazolidinedithiones to 5,7-dihydrodiimidazo[4,5-b:4',5'-e]pyrazine-2,6(1H,3H)-diones and -dithiones (1985)
    s.l. : American Chemical Society
    The @journal of organic chemistry 50 (1985), S. 3431-3434 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00219a001
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  • 2
    Electronic Resource
    Electronic Resource
    Thiirene als Zwischenstufen der Thermolyse von 1,2,3-Thiadiazolen (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1769-1778 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thiirenes as Intermediates in the Thermolysis of 1,2,3-ThiadiazolesThermolysis of the isomeric thiadiazoles 1a or 1b in moist 2,2′-oxydiethanol (3) yields the ketone 6, the thiophene 7, the alkyne 8, and the disulfide 11, the structure of which was determined by an X-ray analysis. In the presence of diphenylacetylene (15) 1a and 1b react to give the thiophenes 16a and 16b in the same ratio. This implies that the primary products of thermolysis, the 1,3-diradicals 13, can be trapped by alkynes. The formation of identical thiophenes from isomeric thiadiazoles 1 can be understood in terms of an equilibrium between the primary fragments 13 via the thiirene 14. Similarly, the ketone 6 seems not to result from 8 but from 14.
    Notes: Bei der Thermolyse der stellungsisomeren Thiadiazole 1a oder 1b in feuchtem 2,2′-Oxydiethanol (3) entstehen das Keton 6, das Thiophen 7, das Alkin 8 und das durch eine Röntgenstrukturanalyse eindeutig aufgeklärte dimere Disulfid 11. In Gegenwart von Diphenylacetylen (15) bilden sich aus 1a und 1b die Thiophene 16a und 16b im selben Verhältnis. Die bei der Thermolyse zunächst entstehenden 1,3-Diradikale 13 können demnach durch Alkine abgefangen werden. Die Bildung identischer Thiophene aus isomeren Thiadiazolen 1 läß sich durch ein Gleichgewicht der Primärfragmente 13 verstehen, das sich über das Thiiren 14 einstellt. Auch das Keton 6 scheint nicht aus 8, sondern aus 14 zu entstehen.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120528
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  • 3
    Electronic Resource
    Electronic Resource
    Verdrillte Oxalsäurederivate Die Kristall- und Molekülstruktur von N,N,N′,N′-Tetramethyloxamid und -monothiooxamid (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 1159-1166 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Twisted Oxalic Acid Derivatives The Crystal and Molecular Structure of N,N,N′,N′-Tetramethyloxamide and -monothiooxamideThe structures of the title compounds (2 and 3) have been determined from X-ray data, and refined to R = 0.065 (2) and 0.057 (3) respectively. 2 crystallizes in the space group C2/c, 3 in the space group P21/c. - In the crystal 2 exhibits a configuration in which the two halves of the molecule are twisted by 71.4°. This angle amounts to 87.4° in 3.
    Notes: Die Strukturen der Titelsubstanzen (2 und 3) wurden röntgenographisch bestimmt und bis zu R-Werten von 0.065 (2) bzw. 0.057 (3) verfeinert. 2 kristallisiert in der Raumgruppe C2/c, 3 in der Raumgruppe P21/c. - 2 liegt im Kristall in einer Konfiguration vor, bei der die beiden Molekülhälften um 71.4° gegeneinander verdrillt sind; bei 3 beträgt dieser Winkel 87.4°.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100339
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  • 4
    Electronic Resource
    Electronic Resource
    The 2,4-Bis(diphenylmethylene)-1,3-cyclobutane-dione Diradical Dianion and its Sulphur Analogues2) (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1397-1402 
    Details
    ISSN: 0009-2940
    Keywords: Cyclobutane-1,3-diones ; Cyclobutane-1,3-dithiones ; Radical anions ; Diradical dianions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,4-Bis(diphenylmethylene)-1,3-cyclobutanedione (1) is transformed into its sulphur analogues 2 and 3 with Lawesson's or Davy's reagent 5a,b. An X-ray structural analysis is performed on 3. The electrochemistry of these compounds is surveyed. The products of the electrochemical reduction exhibit ESR spectra, which could not be attributed to the radical anions 1-•, 2-•, and 3-•. Extensive semiempirical AM1/Cl calculations suggest the spectra to correspond to the diradical dianions. The experimental data are discussed in terms of the theoretical results.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240613
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  • 5
    Electronic Resource
    Electronic Resource
    Kristall- und Molekülstruktur eines Ketens, eines Thioketens und eines Thioketen-S-oxids (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 2698-2708 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Crystal and Molecular Structures of a Ketene, a Thioketene, and a Thioketene S-OxideStarting from the thioketene 8, the corresponding ketene 7 is accessible via oxidative desulfurization by 1-pyrroline 1-oxides and the thioketene S-oxide 9 by oxidation with a peracid: 9 is isolated as a mixture of diastereomers 9a,b, The structures of the heterocumulenes 7,8, and 9a have been determined from X-ray data and refined to R = 0·063 (7), 0·051 (8), and 0·068 (9a), respectively. In accordance with considerations based on hybridisation, the heterocumulene system in 7, 8, and 9a is linear, but the oxygen atom in 9a is bent off in the mirror plane of the molecule. By comparison with literature data, the bond distances in the heterocumulene moiety of 7, 8, and 9a allow insights into the electron-distribution in various classes of heterocumulenes. The comparison of 7, 8, and 9a with one another reveals striklingly low variations of the C = C distance.
    Notes: Ausgehend vom Thioketen 8 sind durch oxidative Entschwefelung mit 1-Pyrrolin-l-oxiden das Keten 7 und durch Persäure-Oxidation das Thioketen-S-oxid 9 zugänglich, das als Diastereomerengemisch 9a, b anfällt. Die Strukturen der Heterocumulene 7,8 und 9a wurden röntgenographisch bestimmt und bis zu R-Werten von 0·063 (7), 0·051 (8) bzw. 0·068 (9a) verfeinert. Im Einklang mit Hybridisierungsvorstellungen ist das Heterocumulensystem in 7, 8 und 9a linear, aber das Sauerstoffatom in 9a in der Spiegelebene des Moleküls abgewinkelt. Die Bindungslängen im Heterocumulenteil von 7,8 und 9a erlauben im Vergleich mit Literaturdaten Aufschlüsse über die Elektronenverteilung in verschiedenen Heterocumulen-Klassen. Der Vergleich von 7,8 und 9a untereinander zeigt auffallend geringe Änderungen im C = C-Abstand.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120738
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  • 6
    Electronic Resource
    Electronic Resource
    Thioketen-Synthesen, VII. Thioketene durch [3 + 2]-Cycloreversion von 1,3-Dithiolan-Derivaten (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 1165-1175 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thioketene Syntheses, VIII.  -  Thioketenes by [3+2] Cycloreversion of 1,3-Dithiolane Derivatives2-Alkylidene-1,3-dithiolanes are transformed into S,S-dioxides 1 and S-ethyl- 2 or S-arylsulfonium salts 3. After deprotonation at C-5 they form in a [3 + 2] cycloreversion thioketenes 5, which can be trapped as thioamides 17, 18. The stabilized thioketenes 5e, i-k afford 1:1 cycloadducts 24a, b, 27a-d with azomethines; in addition, thioketene 5j provides a dimer 28j, which was characterized by an X-ray structural investigation.
    Notes: 2-Alkyliden-1,3-dithiolane werden in S,S-Dioxide 1 und S-Ethyl-2 oder S-Arylsulfonium-Salze 3 übergeführt. Nach Deprotonierung an C-5 bilden sich in einer [3 + 2]-Cycloreversion Thioketene 5, die als Thioamide 17, 18 abgefangen werden können. Die stabilisierten Thioketene 5e,i-k liefern mit Azomethinen 1: 1-Cycloaddukte 24a,b, 27a-d; das Thioketen 5j reagiert daneben zu einem Dimeren 28j, das durch Röntgenstrukturanalyse charakterisiert wurde.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210624
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  • 7
    Electronic Resource
    Electronic Resource
    Kurzmitteilung/Short Communication Generation and Trapping of Dichlorothioketene (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1485-1487 
    Details
    ISSN: 0009-2940
    Keywords: Thioketenes ; Flash-vacuum pyrolysis ; Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash-vacuum pyrolysis of 2,4-bis(dichloromethylene)-1,3-dithietane (1) at 820°C furnishes dichlorothioketene (2a) which may be trapped with cyclopentadiene (3) in a [4+2] cycloaddition. The constitution 4a of the product is confirmed by an X-ray structural analysis of the related cycloadduct 4b.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240626
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  • 8
    Electronic Resource
    Electronic Resource
    The 2,4-Bis(diphenylmethylene)-1,3-cyclobutane-dione Diradical Dianion and Its Sulphur Analogues (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1885-1885 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240832
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  • 9
    Electronic Resource
    Electronic Resource
    Unerwartete Diels-Alder- und Oxidations-Reaktionen von Benzo[c]thiophenen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 2065-2068 
    Details
    ISSN: 0009-2940
    Keywords: Benzo[c]thiophenes ; Oxidation ; Quinones ; Sulfines ; Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unexpected Diels-Alder and Oxidation Reactions of Benzo[c]thiophenesThe oxidation of thiophenes by peracids to form thiophene S-oxides could not be carried out with benzo[c]thiophenes. With the sterically hindered compound 1a the quinones 2 and 3 were produced whereas the anisyl-substituted derivative 1b formed the sulfine 5. Significantly different behaviour of 1a and 1b was also observed for the Diels-Alder reaction with N-phenylmaleimide. The unexpected and unusual adduct 6 was the only product formed from 1a, with low yield though, whereas the normal Diels-Alder adduct was obtained from 1b.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901231019
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  • 10
    Electronic Resource
    Electronic Resource
    New Cyclopropyl Building Blocks for Organic Synthesis, 21. Diels-Alder Reactions of Methyl 2-Chloro-2-cyclopropylideneacetate with Electron-Rich Dienes: Synthesis of Potential Intermediates for Illudin M (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1051-1064 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopropyl building blocks ; Strained compounds ; [4 + 2] Cycloaddition ; Regioselectivity ; Epoxides, regioselective cleavage of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Ethoxy- (8a) and 1-(trimethylsilyloxy)-1,3-pentadiene (8b) cycloadded to 2-chloro-2-cyclopropylideneacetate 6 to give low yields of endo/exo-9a and -9b, respectively. On the other hand, furans 5a-d added 6 (5b and 5d reacted regioselectively) to afford mixtures of the corresponding [4 + 2] cycloadducts endo-11a-d and exo-11a-d in good to high yields. 2-Methyl-5-(trimethylsilyloxy)furan (5e) yielded a mixture of the four cycloadducts endo/exo-11e and endo/exo-12e, which upon attempted purification on silica gel underwent facile hydrolysis to give bicyclic hemiacetals endo/exo-13 and 4-hydroxycyclo-2-hexen-1-ones endo/exo-14, respectively. Similarly endo/exo-11f, and endo/exo-12f, obtained from 2-methoxy-5-methylfuran (5f) and 6, upon hydrolysis in the presence of silica gel gave endo/exo-13 and endo/exo-14 respectively. The structures of endo-14 and exo-12f were established by X-ray crystallography. In the presence of florisil, the epoxides endo-and exo-16 were formed from trimethylsilyloxy-substituted cycloadducts endo/exo-11e. Selective reduction of the α-chlorocarboxylate functionality in the cycloadducts endo-11a-d,f with LiBH4, followed by base-catalyzed cyclization of the resulting chlorohydrins endo-21a-d, f yielded the corresponding epoxides endo-22a-d,f in 22-73% overall yield. Under identical conditions, the cycloadducts exo-11a-f could not be reduced to the corresponding chlorohydrins exo-21a-f. Regioselective reduction of the acetal epoxide endo-22f to the tertiary alcohol endo-23f was achieved with sodium dihydrobis(2-methoxyethoxy)aluminate (Red-Al®). On stirring with moist silica gel, the bicyclic acetals endo-22d,f and endo-23f cleanly hydrolysed to the highly substituted spiro[2.5]oct-6-en-5-ones endo-24d,f (26 and 24% overall yields, respectively, in four steps from 5d,f and 6) and endo-25f, respectively (23% overall yield in five steps from 5f and 6).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270614
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