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  • 1
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 761-768 
    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 Structure of Bis(di-tert-butylmethyl) OxalateThe structure of the title compound (4) has been determined from X-ray data and refined to R = 0.048. 4 crystallizes in the space group C2/c with lattice parameters a = 23.599(4) Å, b = 12827(1) Å, C = 15.272(2) Å and β = 108.89(2)°. - The molecule exhibits the unusual Z-configuration. Bond lenghts and angles show no particularities with the exception of the central C—C-bond which appears significantly short (a = 1.531 Å).
    Notes: Die Struktur der Titelsubstanz (4) wurde röntgenorgraphisch bestimmt und bis zu einem R von 0.048 verfeinert. 4 kristallisiert in der Raumgruppe C2/c mit den Zellparametern a = 23.599(4) Å, b = 12.827 (1) Å, c = 15.272(2) Å und β = 108.89(2)°. - Das Molekül liegt in der ungewöhnlichen Z-Konfiguration vor. Bindungslängen und -winkel zeigen mit Ausnahme der zentralen C—C-Bindung, die mit A = 1.531 Å relativ kurz erscheint, normale Werte.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 1159-1166 
    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
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 55-65 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloaddition Reactions of Heterocumulenes, XXVI. Cycloadducts from Aryl Isothiocyanates and 2,2-Disubstituted EnaminesAryl isothiocyanates 1 react with enamines 2 to give two types of 2:1 cycloadducts. Below 50°C, 1a - g and 2 give rise to 6-imino-1,3-thiazine-2-thiones 5, the constitutions of which are proved by an X-ray analysis of 5c. Above 50°C or starting from 4-nitrophenyl isothiocyanate (1h),2,4-dithiouracils 6 are formed. 1:1 cycloadducts of the reactants are detected spectroscopically; on workup, they hydrolyze to give 2-formylthiopropionanilides 9.
    Notes: Arylisothiocyanate 1 und Enamine 2 reagieren zu zwei Typen von 2:1-Cycloaddukten. Unterhalb von 50°C entstehen aus 1a - g und 2 6-Imino-1,3-thiazin-2-thione 5, deren Konstitution durch die Röntgenstrukturanalyse von 5c bewiesen wurde. Oberhalb 50°C oder aus 4-Nitrophenylisothio-cyanat (1h) bilden sich 2,4-Dithiouracile 6. 1:1-Cycloaddukte der Reaktanten lassen sich spektroskopisch nachweisen; bei der Aufarbeitung hydrolysieren sie zu 2-Formylthiopropionaniliden 9.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2516-2525 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloaddition Reactions of Heterocumulenes, XXIV. Selenazole Derivatives from Carbon Diselenide and 3-(Dimethylamino)-2H-azirines3-Selenazolines 5 result from the reaction of carbon diselenide (1) with 2-phenyl-substituted azirines 2a,b via 1,2-cleavage. In the 2,2-dimethylazirine 2c 1 induces 1,3-ring-opening to give the zwitterionic selenazoline 8a which in solution exists exclusively as isoselenocyanate 8B. Reactions of 8 are possible from form A as well as from B. The 2-monosubstituted azirine 2d reacts with 1 to give the 2,2′-biselenazole 23 and the 1-selenomesoxaldiamide 24. The constitution 23 was derived from an X-ray structural analysis.
    Notes: Aus Carbondiselenid (1) und den 2-Phenyl-substituierten Azirinen 2a, b entstehen unter 1,2-Bindungsspaltung die 3-Selenazoline 5. Beim 2,2-Dimethylazirin 2c bewirkt 1 1,3-Ringöffnung zum zwitterionischen Selenazolin 8a, das in Lösung ausschließlich als Isoselenocyanat 8B vorliegt. Reaktionen von 8 sind sowohl aus der Form A wie aus B möglich. Das 2-monosubstituierte Azirin 2d gibt mit 1 das 2.2′-Biselenazol 23 und das 1-Selenomesoxalsäure-diamid 24. Die Konstitution 23 ergibt sich aus einer Röntgenstrukturanalyse.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3792-3798 
    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 Structure of O,O′-Diethyl 5-tert-ButyldithioisophthalateThe structure of the title compound (4) has been determined from X-ray data by means of direct methods and refined to R=0.057. 4 crystallizes in the space group P1¯.  -  The molecule is approximately planar; the interplanar angles between the plane of the benzene ring and those of the RO—CS-groups being 5.3° and 7.6°, respectively. The C=S bond length of 1.631 ± 0.002 Å points to a moderate double bond character.
    Notes: Die Struktur der Titelsubstanz (4) wurde röntgenographisch mit Hilfe der Direktmethode bestimmt und bis zu einem R von 0.057 verfeinert. 4 kristallisiert in der Raumgruppe P1¯.  -  Das Molekül ist fast eben gebaut; die Interplanarwinkel zwischen der Ebene des Benzolrings und denen der RO—CS-Gruppen betragen 5.3° und 7.6°. Die C=S-Bindungslänge von 1.631 ± 0.002 Å läßt auf einen mäßig ausgeprägten Doppelbindungscharakter schließen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 1685-1692 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Formation, Reactions, Crystal and Molecular Structure of the Cyclic Sulfenylcarboxylate: Methyl 3-Oxo-3H-2.1-benzoxathiole-7-carboxylateOn heating of 2-(benzylsulfinyl)isophthalic acid (4) with acetic acid/acetic anhydride the cyclic sulfenylcarboxylates 7a and 7b are formed in an unexpected elimination reaction and rearrangement, respectively. 7a can be methylated to the title compound 7c. The structure of 7c has been determined from X-ray data and refined to R = 0.06. 7c crystallizes in the monoclinic system, space group P21/c. The molecule is nearly planar and reveals an intramolecular interaction which is reflected in a short S…‥O distance of 252 pm and an unusual IR spectrum (νCO 1750. 1650 cm-1).
    Notes: In einer unerwarteten Eliminierungsreaktion bzw. Umlagerung bilden sich beim Erhitzen von 2-(Benzylsulfinyl)isophthalsäure (4) mit Essigsäure/Essigsäureanhydrid die cyclischen Carbonsäure-Sulfensäureanhydride 7a und 7b. 7a kann zur Titelverbindung 7c methyliert werden. Die Struktur von 7c wurde röntgenographisch bestimmt und bis zu R = 0.06 verfeinert. 7c kristallisiert monoklin in der Raumgruppe P21/c. Das Molekül ist fast planar und zeigt intramolekulare Wechselwirkung, die an einem geringen S…‥O-Abstand (252 pm) und einem ungewöhnlichen IR-Spektrum (νCO 1750, 1650 cm-1) erkannt werden kann.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1769-1778 
    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
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