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  • 1
    Electronic Resource
    Electronic Resource
    Zur Struktur der Produkte der Reaktion vonE/Z-1-Benzolsulfonyl-3-(1-pentenyl)-indol mit N-Phenylmaleinimid: Ein erster Beitrag zur Konfigurations- und Konformationsanalyse in der Vinylindol-Cycloadditionsreihe (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 1289-1297 
    Details
    ISSN: 1434-4475
    Keywords: 3-Vinylindoles ; Cycloadducts ; 1H-NMR ; X-Ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The products2,3 of the reaction ofE/Z-1-benzenesulfonyl-3-(1-pentenyl)-indole (1) and N-phenylmaleimide were analysed by1H-NMR spectroscopy. Exemplarily, the structure elucidation of theendo-cyclo-adduct2 b was achieved by using several NMR techniques (diff. NOE-, INDOR-measurements, decoupling experiments, spectra simulation). The1H-NMR-spectroscopically gained prediction of relative configuration and conformation of2 b was supported on X-ray analysis. The cyclohexene ring of the new cycloadducts adopts in the liquid phase and in the crystal a slightly twisted boat conformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808309
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  • 2
    Electronic Resource
    Electronic Resource
    (-)-(M,7S)-Colchicine and (-)-(M,7S)-10-Ethylthiocolchicide/Alkyne Cycloaddition Reactions: Synthesis of Novel Colchicine Derivatives by Consecutive [4+2] and [3+2] Cycloadditions (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2451-2460 
    Details
    ISSN: 1434-193X
    Keywords: Colchicine ; 10-Ethylthiocolchicide, diene properties of ; π-Facial diastereoselectivity ; Consecutive [4+2],[3+2] cycloadditions ; Atropisomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloaddition reactions of the facially dissymmetric diene moiety of (-)-(M,7S)-colchicine (5) and (-)-(M,7S)-10-ethylthiocolchicide (9) to various alkynes have been studied. With 5 and the dienophilic benzyne (3), dimethyl acetylenedicarboxylate (DMAD) (4) and cyclooctyne (6) as starting materials all cycloadditions could be realized with high regioselectivity at the 8,12-positions of the alkaloid. The approach of the dienophiles preferentially occurred toward the syn π-face of the diene. In contrast to the cycloaddition mode of 5 the ethylthiocolchicide 9 surprisingly reacted in a different manner. With benzyne as starting material a novel [3+2] cycloaddition of the thioenol ether moiety of 9 towards the dipolarophilic benzyne is supposed, affording the unexpected colchicide 10 after [1,5]H shift of the primarily formed cycloadduct followed by cleavage of the C-S linkage. With DMAD (4) and cyclooctyne (6) the reaction course is more complex. In a consecutive [4+2]/[3+2] cycloaddition (or vice versa) followed by a thermally induced cycloreversion of a not identified intermediate DMAD (4) gives rise to the polycyclic thiophene derivative 13 and the novel allocolchicinoid 14. In a similar way cyclooctyne (6) yielded three products, the thiophene-annulated homobarrelenones 18 and 19 and the tetracyclic allocolchicinoid 21. The structures of the novel colchicine derivatives were assigned on the basis of spectral data, those of the cycloadducts 1 and 19 were verified by X-ray crystallography. For the unprecedented formation of the various allocolchicinoids by consecutive [4+2]/[3+2] cycloadditions plausible reaction pathways are suggested, as far as possible. In addition the inhibitory effects on the tubulin polymerization reaction in vitro of 10, 14, and 21 are reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Positional and Facial Selectivity in Diels-Alder Reactions of (-)-(aS,7S)-Colchicine: Synthesis of Novel Analogues of the Alkaloid (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 851-857 
    Details
    ISSN: 0947-3440
    Keywords: Colchicine, diene properties of ; Positional selectivity ; Stabilized exciplex through hydrogen bonding ; π-Facial diastereoselectivity ; Photooxygenation ; Solvent effects ; Cycloadditions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positional and facial selectivity in Diels-Alder reactions of several hetero- and carbodienophiles with (-)-(aS,7S)-colchicine (1) has been examined. In all cases, cycloaddition occurred with high positional selectivity at the 8,12-positions of the alkaloid and preferentially from the diene face syn to the allylic substituent at the stereogenic center C-7. The observed high π-facial diastereoselectivity is independent of the polarity of the solvent used and is therefore probably a consequence of steric factors. The structures of the Diels Alder-adducts of 1 with singlet oxygen, N-phenyl-1,2,4-triazolinedione (PTAD) and trans-cyclooctene, 4,5, and 15, respectively, were assigned on the basis of spectral data and verified by X-ray crystallography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970510
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  • 4
    Electronic Resource
    Electronic Resource
    1,3-Dithienium- und 1,3-Dithioleniumsalze. IX. Reaktionen von 1,3-Dithian-2-ylium-tetrafluoroboraten mit C-Nucleophilen (1998)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 340 (1998), S. 63-72 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Dithienium and 1,3-Dithiolenium Salts. IX. Reactions of 1,3-Dithiane-2-ylium Tetrafluoroborates with C-Nucleophiles1,3-Dithian-2-ylium tetrafluoroborates (1), which can be easily obtained by variable methods, react in good to excellent yields with variable C-nucleophiles to new geminal disubstituted 1,3-dithianes. The latter compounds are potential precursors of interesting synthetic building blocks. Reactions are described with 2-lithio-1,3-dithianes 2, sodium cyanide 4, sodium salts of the nitro alkanes 7 and CH-acids of the type of the 1,3-dicarbonyl compounds 9. The reduction of 3-oxo-2-(2-phenyl-1,3-dithian-2-yl)-ethoxybutanoat-following a diastereoselective pathway - leads to the Cram product 11. Further presented is the crystal structure of 2-phenyl-1,3-dithiane-2-ylium tetrafluoroborate (1b).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19983400110
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  • 5
    Electronic Resource
    Electronic Resource
    Wanzlick-Carbene in der [4 + 1]-Cycloaddition mit Bis(methylthio)- und Bis(trifluormethyl)-1,2,4,5-tetrazin (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1803-1806 
    Details
    ISSN: 0009-2940
    Keywords: Singlet carbenes ; [4 + 1] Cycloadditions ; 1,2,4,5-Tetrazines ; SEAr reactions, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Wanzlick Carbenes in the [4 + 1] Cycloaddition Reaction with Bis(methylthio)- and Bis(trifluoromethyl)-1,2,4,5-tetrazineThe 3,6-disubstituted 1,2,4,5-tetrazines 3 and 4 have been submitted to a [4 + 1] cycloaddition reaction with the nucleophilic singlet carbenes (Wanzlick carbenes) 2a-d, which are generated from the precursors 1a-d. With 3 as diazadiene the expected spiro compounds 6a-d are formed. In contrast to this presumed two-step reaction sequence of 3, with the tetrazine 4 the cascade cycloaddition/cycloelimination is surprisingly followed by an intramolecular electrophilic aromatic substitution to yield the chiral tetracyclic compounds of type 8 with high diastereoselectivity. The crystal structure of 8d has been determined by X-ray diffraction methods.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270933
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  • 6
    Electronic Resource
    Electronic Resource
    Azaazulene als Dienophile in der Diels-Alder-Cycloaddition mit 3,6-Bis(trifluormethyl)1-1,2,4,5-tetrazin (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 441-445 
    Details
    ISSN: 0009-2940
    Keywords: Azaazulenes ; 1,2,4,5-Tetrazine ; [4 + 2] Cycloadditions, “inverse” ; Azaazulene-quinoline rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azaazulenes as Dienophiles in the Diels-Alder Cycloaddition with 3,6-Bis(trifluoromethyl)1-1,2,4,5-tetrazineThe LUMO-diene-controlled [4 + 2] cycloaddition of the azaazulenes 6 and 17 with the tetrazine 1, one of the most reactive diazadienes “with inverse electron demand”, are described. Like azulene (2) the azaazulenes 6a, b react with 1 - probably by a two-step mechanism via the dipolar species 7 - to yield the adduct 8; N2 elimination leads to 9, which rearranges to the pyridazo[4,5-c]quinoline 13 and the azine-substituted 1-azaazulene 12. In a rather complex reaction sequence the 2-azaazulene 17 forms the salt 18; the crystal structure of 18 has been determined by X-ray diffraction methods.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260222
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  • 7
    Electronic Resource
    Electronic Resource
    Synthese homochiraler 3-Oxa-2,7-diazabicyclo[3.3.0]octane aus Aminosäuren durch intramolekulare 1,3-dipolare Cycloaddition von Nitronen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 787-795 
    Details
    ISSN: 0009-2940
    Keywords: Heterobicyclo[3.3.0]octanes, homochiral ; Amino acids ; Nitrones ; Cycloadditions, diastereoselective, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Homochiral 3-Oxa-2,7-diazabicyclo[3.3.0]octanes from Amino Acids by Intramolecular 1,3-Dipolar Cycloaddition of NitronesN1-Allylamino alcohols 9 were prepared from amino acids by various methods. Swern oxidation of 9 afforded aldehydes 11. By reaction of 11 with N1-alkylhydroxylamines nitrone intermediates 4 were formed which spontaneously underwent an intramolecular 1,3-dipolar cycloaddition to yield the bicyclic compounds 6. The cycloaddition proceeds diastereoselectively furnishing homochiral compounds 6 from homochiral starting materials. The structure of 6aA was confirmed by X-ray structural analysis.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260333
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  • 8
    Electronic Resource
    Electronic Resource
    Thermisch induzierte formale [3 + 2]-Cycloadditionen von 3,3-Dimethoxycyclopropen an Triazine, eine neue Synthese von Pyrrolo[1,2-d][1,2,4]triazinen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2317-2323 
    Details
    ISSN: 0009-2940
    Keywords: 1,2,4-Triazines ; [3 + 2] Cycloadditions ; Singlet vinylcarbene ; 1,3-Dipole, three-carbon ; Pyrrolo[1,2-d][1,2,4]triazines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermally Induced Formal [3 + 2] Cycloadditions of 3,3-Dimethoxycyclopropene to Triazines, a Novel Synthesis of Pyrrolo[1,2-d][1,2,4]triazinesFormal [3 + 2] cycloaddition reactions of the π-delocalized singlet vinylcarbene/three-carbon 1,3-dipole 8, generated in a reversible, thermal ring opening of the cyclopropenone ketal 7, with a variety of substituted triazines lead to the novel pyrrolo[1,2-d][1,2,4]triazines 9 or 10. Compound 10c is protonated at N-2 by HClO4/HOAc to yield the salt 17c and alkylated at the same position by Meerwein reagent [O(CH3)3BF4] to give 18. 10c reacts smoothly with dimethyl acetylenedicarboxylate to provide the pyrido[2,1-f]pyrrolo[1,2-d][1,2,4]triazines 19 and 20. The pyrrolotriazine 14 in the presence of oxygen, daylight, and silica gel is readily oxidized to the triazine N-oxide 22. The crystal structures of 14, of the protonated species 17c and of the N-oxide 22 have been determined by X-ray diffraction methods.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261021
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  • 9
    Electronic Resource
    Electronic Resource
    [SbCl([15]Krone-5)](SbCl6)2 und [BiCI([18]Krone-6)(CH3CN)2](SbCl6)2: Salze mit Antimon(III)- und Bismut(III)-DikationenProfessor Wolfgang Beck zum 60. Geburtstag gewidmet (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 104 (1992), S. 354-356 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19921040336
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  • 10
    Electronic Resource
    Electronic Resource
    Die Kristallstrukturen von (NH4)2[ReCl6], [ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN und [ReCl4(18-Krone-6)] (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 525-530 
    Details
    ISSN: 0044-2313
    Keywords: Rhenium Complexes ; Syntheses ; IR spectra ; Crystal Structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Crystal Structures of (NH4)2[ReCl6], [ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN and [ReCl4(18)(Crown-6)]Brown single crystals of (NH4)2[ReCl6] are formed by the reaction of NH4Cl with ReCl5 in a suspension of diethylether. [ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN crystallizes as brown crystal plates from a solution of ReCl5 in acetonitrile. Lustrous green single crystals of [ReCl4(18-crown-6)] are obtained by the reaction of 18-crown-6 with ReCl5 in a dichloromethane suspension. All rhenium compounds are characterized by IR spectroscopy and by crystal structure determinations.(NH4)2[ReCl6]: Space group Fm3m, Z = 4, 75 observed unique reflections, R = 0.01. Lattice constant at -70°C: a = 989.0(1) pm. The compound crystallizes in the (NH4)2[PtCl6] type, the Re—Cl distance is 235.5(1) pm.[ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN: Space group P1, Z = 1, 2459 observed unique reflections, R = 0.12. Lattice dimensions at -60°C: a = 859.0(1), b = 974.2(7), c = 1287.3(7) pm, α = 102.69(5)°, b̃ = 105.24(7)°, γ = 102.25(8)°. The structure consists of two symmetry-independent [ReCl2(CH3CN)4]+ ions with trans chlorine atoms, [ReCl6]2- ions, and included acetonitrile molecules. In the cations the Re—Cl bond lengths are 233 pm in average, in the anion they are 235 pm in average.[ReCl4(18-crown-6)]: Space group P21/n, Z = 4, 3 633 observed unique reflections, R = 0.06. Lattice dimensions at -70°C: a = 1040.2(4), b = 1794.7(5), c = 1090.0(5) pm, b̃ = 108.91(4)°. The compound forms a molecular structure, in which the rhenium atom is octahedrally coordinated by the four chlorine atoms and by two oxygen atoms of the crown ether molecule.
    Notes: Braune Einkristalle von (NH4)2[ReCl6] entstehen durch Reaktion von NH4Cl mit ReCl5 in einer Diethylethersuspension. [ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN kristallisiert als braune Kristallplättchen aus einer Lösung von ReCl5 in Acetonitril. Leuchtend grüne Einkristalle von [ReCl4(18-Krone-6)] entstehen durch Reaktion von 18-Krone-6 mit ReCl5 in einer Dichlormethansuspension. Die drei Rhenium-Verbindungen werden durch ihre IR-Spektren und durch Kristallstrukturanalysen charakterisiert.(NH4)2[ReCl6]: Raumgruppe Fm3m, Z = 4, 75 unabhängige beobachtete Reflexe, R = 0,01. Gitterkonstante bei -70°C: a = 989,0(1) pm. Die Verbindung kristallisiert im (NH4)2[PtCl6]-Typ, der Re—Cl-Abstand beträgt 235,5(1) pm.[ReCl2(CH3CN)4]2[ReCl6] · 2CH3CN: Raumgruppe P1, Z = 1, 2459 beobachtete unabhängige Reflexe, R = 0,12. Gitterkonstanten bei -60°C: a = 859,0(1); b = 974,2(7); c = 1287,3(7) pm, α = 102,69(5)°; b̃ = 105,24(7)°; γ = 102,25(8)°. Die Struktur besteht aus zwei symmetrieunabhängigen [ReCl2(CH3CN)4]+-Ionen mit trans-ständigen Chloratomen, [ReCl6]2--Ionen und eingelagerten Acetonitrilmolekülen. In den Kationen betragen die Re—Cl-Abstände im Mittel 233 pm, im Anion im Mittel 235 pm.[ReCl4(18-Krone-6)]: Raumgruppe P21/n, Z = 4, 3 633 beobachtete unabhängige Reflexe, R = 0,06. Gitterkonstanten bei -70°C: a = 1040,2(4); b = 1794,7(5); c = 1090,0(5) pm; b̃ = 108,91(4)°. Die Verbindung bildet eine Molekülstruktur, in der das Rheniumatom oktaedrisch von den vier Chloratomen und von zwei Sauerstoffatomen des Kronenethers koordiniert ist.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210404
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