Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Towards the Synthesis of o-Diphosphaquinones: Benzodiphosphadihydropentalene - Naphthodihydrodiphosphete (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 121-125 
    Details
    ISSN: 0947-3440
    Keywords: Propargyl rearrangement ; DBU ; Electrocyclization ; Diphosphaquinone ; Dihydrodiphosphete ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: o-Quinodimethanes 1 are important intermediates in organic synthesis that may be generated by thermal valence isomerization of benzocyclobutenes[1] or octa-1,2,4,6,7-pentaenes[2]. The preparation of a stable o-quinodimethane has not been reported so far. Whereas o-quinodiimines 2 containing strongly electron-withdrawing groups at the nitrogen atoms are isolable[3], o-diphosphaquinones 3 have not been detected.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970118
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    An Unorthodox Pathway to the 1,2-Dithiin SystemDedicated to Professor Wolfgang Beck, München, on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1677-1684 
    Details
    ISSN: 0947-3440
    Keywords: 1,2-Dithiin ; Cycloadditions ; Sulfur extrusion ; Thiophenes ; Reaction mechanisms ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetracyanoethylene combines with two molecules of thiobenzophenone in refluxing benzene to give the tetrasubstituted 1,2-dithiin 8 (21-29%) besides the corresponding thiophene derivative 9 (40-52%). The X-ray analysis of the ruby-red 8 reveals a half-chair conformation with a torsion angle of 58.9° at the disulfide bond. The thermal desulfurization 8 → 9 (benzonitrile, 100°C) proceeds with t1/2 = 26.7 h, whereas the sulfur loss induced by triethyl phosphite is a billion times faster. The mechanisms of the formation of 8 and its sulfur extrusion are discussed in the light or recent literature.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970808
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Extrem aufgeweitete Tetrathiafulvalene mit Polyen-Spacern. Carotinoide Tetrathiafulvalene. Polymethin-tetracyanotetrathiafulvalen-Radikalkationen, eine neue Klasse von ViolenenProf. Dr. Siegfried Hünig zum 75. Geburtstag gewidmet (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1497-1517 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extremely Expanded Tetrathiafulvalenes with Polyene Spacers. Carotinoid Tetrathiafulvalenes. Polymethin-Tetracyanotetrathiafulvalene Radical Cations, a New Class of ViolenesThe synthesis of extended tetrathiafulvalenes 11 with di-, tetra-, hexa-, octa-, deca- and dodecamethine spacers is described by a PPh3-induced Wittig-reaction-like condensation of the corresponding polyenedials 10 with 2-thio-1,3-dithiole-4,5-dicarbonitrile (9). By the same procedure, the dimethyloctamethine- and the tetramethyl-hexadecamethine-tetrathiafulvalenes 14 and 15, respectively, were obtained. The extended tetrathiafulvalenes represent multistep vinylogous redox systems of the ‘violene type’. They can be oxidized to give the cyanine-like radical cations, e.g. 11sem, 14sem, and 15sem, and the dications, e.g. 11ox, 14ox, and 15ox; their UV/VIS/NIR spectra are reported. The crystal and molecular structure of (all-E)-2,2′-(octa-2,4,6-trien-1,8-diylidene)bis[1,3-dithiole-4,5-dicarbonitrile] (11e) was determined: it is a rod-like, planar molecule; in the crystal, it forms staples along the longest molecule axis. The CV measurements confirm that the redox potentials of 11, 14, and 15 decrease asymptotically with the increasing length of the spacer. Because of the close relationship of the extended tetrathiafulvalenes (ETTF's) to the carotinoids, they are named ‘caroviologenes’; they formally belong to the class of molecular wires.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790522
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Ein erstes Beispiel eines porphyrinoiden Fulvalens: Synthese, Struktur, ESR- und elektrochemische UntersuchungenProf. Dr. Fabian Gerson in Anerkennung seiner Beiträge zum Verständnis von π-Systemen gewidmet (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 2456-2476 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A First Example of a Porphyrinoid Fulvalene: Synthesis, Structure, ESR and Electrochemical InvestigationsThe macrocyclic tetraepoxy-1H-[21]annulen-1-one 4 can by synthesized by the cyclizing Wittig reaction of 5,5′-carbonylbis[furan-2-carboxaldehyde] (11) and the bisphosphonium salt 12, obtained from 2,2′-bifuran-5,5′-dicarboxaldehyde (13). According to an X-ray structure analysis, the annulenone 4 is not planar in the crystal; the 1H-NMR spectra of 4 reveal an averaged planarity with respect to the NMR timescale. The McMurry reaction of 4 yields fulvalene 3 in 43% yield as the most expanded fulvalene hithertoo known. The X-ray structure analyses of 3 surprising establishes a ‘syn’-orientation of the two rings with respect to the central C=C bond, thus forming a basket-like molecule. The 1H-NMR spectrum confirms the averaged planarity of both macrocycles in 3. CV and spectroelectrochemical measurements of 3 suggest a reversible two-electron reduction producing dianion 15 with two aromatic, anionic 5a,15a-didehydro-10H-21,22,23,24-tetraoxa-5a,15a-dihomocorrole (= tetraoxa[22]porphyrin(2.1.2.0)) ring systems containing 22π electrons each. The formation of 15 can also be achieved chemically by reaction of 3 with metallic potassium. The dication 16 of 3 may be antiaromatic, but the exact electronic structure is dubious. ESR and ENDOR investigations on the radical cation and the radical anion of 3 indicate that the free electron is delocalized in the entire molecule.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800814
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Donorsubstituierte 2,4-Diazacyclopentadienone und indigoide 1,3,5,7-TetraazafulvaleneHerr Professor Dr. Karl Gewald zum 60. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 949-967 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Donor Substituted 2,4-Diazacyclopentadienones and Indigoid 1,3,5,7-TetraazafulvalenesHydrolysis of tris(diethylamino)imidazolylium chloride gives rise to 2,5-bis-diethyl-amino-4H-imidazolin-4-one; thiolysis leads, depending on conditions, to 2,5-bis-diethylamino-4H-imidazolin-4-thione or potassium 2,6-bis-diethylamino-1,3,5,7-tetraazafulvalene-4,8-dithiolate. The latter can be protonated to form green 2,6-bis(dimethylamino)-3,4,7,8-tetrahydro-1,3,5,7-tetraaza-fulvalen-4,8-dithione, a new indigoid compound, and alkylated to give blue 2,6-bis-diethylamino-4,8-bis-alkylthio-1,3,5,7-tetraazafulvalenes. Treatment of 2,5-bis-diethylamino-4H-imidazolin-4-thione with copper furnishes 2,6,4,8-tetrakis-diethylamino-1,3,5,7-tetraazafulvalene. - Oxidation of 2,6-bis-dimethylamino-3,4,7,8-tetrahydro-1,3,5,7-tetraazafulvalen-4,8-dithione gives rise to (2,2′-bis-diethylamino-4,4′-bi(4H-imidazol)-5,5′-dithione, corresponding to dehydroindigo, and reduction leads to a colorless compound, corresponding to leucoindigo.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320613
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Beiträge zur Chemie des Bors, 113 Zur Darstellung von 1, 1-Bis(diorganylboryl)-2,2-dimethylhydrazinenHerrn Professor Dr. K. Dimroth zum 70. Geburtstag gewidmet. (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 633-641 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Boron, 1131).  -  Synthesis of 1,1 Bis(diorganylboryl)-2,2-di-methylhydrazinesThe lithiohydrazine (CH3)2N-NLi- B(CH3)2 reacts with R2BX (R = CH3, C6H5; X = Cl, Br) yielding 1,1-diboryl-2,2-dimethylhydrazines, 2. Similarly (CH3)3SiCl gives the boryl(silyl)hydrazine 3. 11B-NMR signals for (CH3)2N - N[B(CH3)2]2 (2a) corresponds to a mean value for tri- and tetracoordinated boron. This indicates an association equilibrium which, in the case of (CH3)2N-N[B(CH3)2]B(C6H5)2 lies fully on the side of the dimer.
    Notes: Aus dem Lithiohydrazin (CH3)2N-NLi-B(CH3)2 und R2BX (R = CH3, C6H5; X = Cl, Br) wurden die 1,1-Diboryl-2,2-dimethylhydrazine 2, mit (CH3)3SiCl wurde das Boryl(silyl)hydrazin 3 erhalten. Das monomere (CH3)2N-N[B(CH3)2]2 (2a) zeigt ein 11B-NMR-Signal mit einer chemischen Verschiebung, die einem Mittelwert für drei- und vierfach koordiniertes Bor entspricht. Ein Assoziationsgleichgewicht ist dafür verantwortlich. Dieses liegt im Falle des (CH3)2N-N[B(CH3)2]B(C6H5)2 völlig auf der Seite eines Dimeren.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119810411
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Beiträge zur Chemie des Bors, 122. Synthese und Reaktivität von TrimethylsilylboranenHerrn Professor Dr. L. Horner zum 70. Geburtstag gewidmet. (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 2067-2080 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Boron, 1221).  -  Synthesis and Reactivity of Trimethylsilylboranes2)LiSi(CH3)3 (4) is a useful reagent in the synthesis of electron-rich trimethylsilylboranes. With aminoboron halides (CH3)3Si-B(NR2)2 or [(CH3)3Si]2B-NR2 are formed. (CH3)3Si[(CH3)2N]B - B-[N(CH3)2]Si(CH3)3 (3) was synthesized in the same way. The product 3 was also obtained by coreduction of (CH3)3SiCl and [(CH3)2N]2BCl. The efficient electronic and steric shielding of the boron atom in (CH3)3Si - B[N(CH3)2]2 (1) and 3 prevent borate formation with 4, however this occurs with [CH3)3Si]2B - N(CH3)2 (6) giving rise to Li[(CH3)3Si]3B - N(CH3)2] (7).  -  The B - Si bond of 1 is found to be rather inert, except to oxidation. Reactions with proton active compounds occur at the B - N bond. Silylboranes with B - Cl or B - O bonds have been obtained in this way. 6 reacts with methanol to produce the adduct [(CH3)3Si]2BOCH3 · HN(CH3)2 which surprisingly dissoziates with elimination of CH3OH. The adduct (CH3)2BOCH3 · HN(CH3)2 is much less stable than the silylborane adduct and decomposes into (CH3)2BOCH3 and dimethylamine.
    Notes: LiSi(CH3)3 (4) ist ein nützliches Reagens zur Darstellung elektronenreicher Trimethylsilylborane. Reaktionen mit Aminoborhalogeniden lieferten (CH3)3Si - B(NR2)2 und [(CH3)3Si]2B - NR2. Auch (CH3)3Si[(CH3)2N]B - B[N(CH3)2]Si(CH3)3 (3) ließ sich so darstellen, ein Produkt, das bei der Koreduktion von (CH3)3SiCi mit ClB[N(CH3)2]2 ebenfalls anfällt. Sowohl bei (CH3)3Si - B[N(CH3)2]2 (1) als auch 3 verhindert die effektive elektronische und sterische Abschirmung des Bors die Borat-Bildung mit 4. Diese erfolgt jedoch aus [(CH3)3Si]2B - N(CH3)2 (6) und 4, wobei Li[(CH3)3Si]3B - N(CH3)2] (7) entsteht.  -  Die B - Si-Bindung in 1 ist  -  außer gegen Oxidation  -  vergleichsweise inert. Reaktionen mit protonenaktiven Verbindungen erfolgen an der B - N-Bindung. Auf diese Weise wurden Silylborane mit B - Cl- bzw. B - O-Bindungen erhalten. Überraschenderweise setzt sich 6 mit Methanol zwar zum Addukt [(CH3)3Si]2BOCH3 · HN(CH3)2 um, das aber vorwiegend wieder unter CH3OH-Abspaltung dissoziiert. (CH3)2BOCH3 · HN(CH3)2 ist wesentlich weniger stabil als das Silylboran-Addukt und zerfällt in (CH3)2BOCH3 und Dimethylamin.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119811115
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...