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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
    Synthesis of 4-silylcyclobut-2-enethiones and their use in cyclobutadiene generation (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 949-956 
    Details
    ISSN: 0947-6539
    Keywords: alkynyl sulfides ; cyclobutadienes ; cyclobutenethiones ; desilylation ; ynamines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkynyl silyl sulfides 2 reacted with ynamines 3 to give 1:1 adducts. The structure of 4-silylcyclobut-2-enethiones 4 was confirmed by X-ray analysis of 4a. A cyclobutadiene intermediate is probably not involved in this reaction; we think that it is initiated by a silyl transfer from 2 to 3, and that this is followed by a combination of the resulting ions to give the unsaturated thioketene 7, which undergoes an electrocyclization to give products 4. In the reaction of thiones 4 with trimethyloxonium tetrafluoroborate (Meerrwein salt) selective methylation at sulfur was observed to give cyclobutenethionium ions 16. Ions 16 underwent fluoride-induced desilylation with various fluoride sources to give cyclobutadienes 17, which could not be isolated, but trapping of 17 a-c was possible with dimethyl acetylenedicarboxylate yielding regioisomeric benzene derivatives 20-23. Similarly, 17 a and bis(methylthio)methylene malononitrile (24) led to hexatriene derivative 27 by a sequence of cycloaddition and two ring-opening reactions. In contrast, silyl-substituted cyclobutadienes 17d,e dimerized even in the presence of trapping agents to anti-tricyclo-[4.2.0.02,5]octadienes 29; this suggests that a two-step cycloaddition is taking place, rather than a concerted Diels-Alder reaction. Attempts to intercept 17d, e, generated from 16d,e with cyclopentadiene (30), gave deprotonation of 30 leading to substitution of the methylthio group in 16 and finally to formation of cyclobutenes 33 through a hydrogen shift.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020807
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  • 3
    Electronic Resource
    Electronic Resource
    Reaction of the Carbanions of 2-(Alkylthio)thiolane 1-Oxides with Oxiranes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1481-1488 
    Details
    ISSN: 1434-193X
    Keywords: Thiolane 1-oxides ; Carbanions ; Oxiranes ; Asymmetric synthesis ; X-ray structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Carbanions of the 2-(alkylthio)thiolane 1-oxides 1 and 2 are generated and subjected to reaction with the epoxides 3-5. The resulting carbinols 6-11 are formed with high α diastereoselectivity, which is explained by a stabilization of the trans configuration of the carbanions in the activated complex. A minor γ stereoselectivity is also observed in case of the reactions with 4 and 5. The pure enantiomers (1S,2S,2′S)-9a and (1R,2R,2′S)-11b were obtained from 2 and (S)-4 or (R)-5, respectively, and their configurations were proved by X-ray structural analyses.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Reactions of N-sulfonylalkylamines with ynamines  -  formation of 2H-1,2-thiazete 1,1-dioxides, novel thioketene S,S-dioxide dimers, and other s,n-heterocycles (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1795-1800 
    Details
    ISSN: 0947-3440
    Keywords: [2 + 2] Cycloadditions ; 2H-1,2-Thiazete 1,1-dioxides ; Amidinosulfenes, in situ formation of ; Diaminothioketene S,S-dioxide ; 1,3-Dithietane 1,1,3,3-tetraoxide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Sulfonylalkylamines 2a, b react with ynamines 3 to give primarily 2H-1,2-thiazete 1,1-dioxides 4. But, except for the 4-triphenylsilyl species 4a, b, these products are unstable and undergo electrocyclic ring opening to very reactive amidinosulfenes 5, which are transformed into different products, depending on the ynamine substituents R2. The 1,3-dithietane 1,1,3,3-tetraoxide 8 is formed from N-sulfonylisopropylamine (2a) and the trimethylsilyl-substituted ynamine 3b via amidinosulfene 5c and probably thioketene S,S-dioxide 7. On the other hand, (isopropylamidino)sulfene 5d dimerizes to the 2H-1,5,2-dithiazine 9 and also gives the [2 + 4] cycloadducts 10a, 11a by reaction with 2a and ynamine 3c, respectively. In contrast, it was possible to trap phenyl-substituted amidinosulfenes 5e-h by addition of water or methanol.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199510251
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  • 7
    Electronic Resource
    Electronic Resource
    Electrophile-induced cyclizations of silyl-substituted 4-alken-1-olsDedicated to Professor Wolfgang Lüttke on the occasion of his 75th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 501-507 
    Details
    ISSN: 0947-3440
    Keywords: Tetrahydrofurans, formation of ; Cyclization, stereocontrolled ; Vinylsilanes ; Allylsilanes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Silyl-substituted 4-alken-1-ols cyclize in the presence of a wide range of electrophilic reagents to give substituted tetra-hydrofurans. The silyl group accelerates ring closure by its β-effect and its position determines the efficiency of stereo-control. Thus, a vinylic silyl group as in 1, 3-9 gives mixtures of 2,5-disubstituted tetrahydrofurans 2, 10-21, favoring formation of the trans isomer. In contrast, an allylic silyl group as in 28-30 exerts a high degree of stereocontrol, generally affording 2,3-trans-disubstituted tetrahydrofurans 31-36.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950369
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of Functionalized Cyclopentanes, Cyclohexanes and Cycloheptanes by a Silicon-Induced Domino Reaction (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1811-1821 
    Details
    ISSN: 0947-3440
    Keywords: Domino reaction ; Functionalized cyclopentanes, -hexanes and -heptanes ; Tetrahydrofurans ; Oxetanes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Functionalized cyclopentanes, -hexanes and -heptanes are obtained by addition of lithiated silyldithioacetals 7 to epoxyhomoallyl tosylates 4-6, The reaction involves a cascade of epoxide ring opening, of Brook 1,4-rearrangement and tosylate substitution. The method is particularly suitable for the preparation of cyclopentanes, whereas cyclohexanes and -heptanes are formed in yields only up to 49%. Use of enantiomerically pure epoxides provides optically active cyclopentanes (S)-10b, d, 11a as well as oxetanes (S)-14a, b. Hydrolysis of the dithioacetal function leads to the corresponding ketones 12, Cyclization of epoxide 24b gives an anellated cyclopentane 26, the configuration of which was established by X-ray structural analysis of dinitrobenzoate 27. Use of epoxide 29b provides the anellated tetrahydrofuran 30.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961115
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  • 9
    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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  • 10
    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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