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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Rb3LnCl6 · 2 H2O (Ln = La—Nd): Darstellung, Kristallstruktur und thermisches Verhalten (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 630-634 
    Details
    ISSN: 0044-2313
    Keywords: Crystal structure ; hydrates of ternary alkali/lanthanide(III) chlorides ; preparation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rb3LnCl6 · 2 H2O (Ln = La—Nd): Preparation, Crystal Structure, and Thermal BehaviourThe compounds Rb3LnCl6 · 2 H2O (Ln = La—Nd) were prepared from acetic acid as powders. The preparation from aqueous solutions does not yield the pure products because RbCl precipitates as first compound. The structure of Rb3LaCl6 · 2 H2O was determined by X-ray analysis of a single crystal obtained from aqueous solution. The compounds with Ln = La—Nd are isotypic. They crystallize hexagonally in the space group P63/m (Rb3LaCl6 · 2 H2O: a = 1 220.4(2) pm, c = 1 688.6(3) (pm) with Z = 6. Anionic trimeric units [Ln3Cl12(H2O)6]3- are stacked along the c-axis over the corners of the unit cell. In the stacking frequency the units are rotated by 60° with respect to each other around the c-axis. The coordination number (C. N.) of Ln3+ is 8, which is satisfied by four bridging and two terminal chloride ions and two water molecules. The coordination spheres of the three rubidium ions in the different atomic positions are composed differently, their C.N. are 9, 8(+1) and 6(+6). The thermal dehydration of the compounds occurs in one step. The hydrates decompose at ca. 100°C to form the anhydrous compounds Rb2LnCl5 und RbCl since the anhydrous chlorides Rb3LnCl6 are thermodynamically stable above ca. 400°C only.
    Notes: Verbindungen Rb3LnCl6 · 2 H2O (Ln = La—Nd) lassen sich feinkristallin aus Eisessig als Lösungsmittel darstellen. Aus wäßriger Lösung lassen sich Einkristalle im Gemisch mit RbCl erhalten. An einem Einkristall von Rb3LaCl6 · 2 H2O wurde eine Strukturanalyse durchgeführt: Raumgruppe P63/m. a = 1 220,4(2) pm, c = 1 688,6(3) pm, Z = 6). Als anionische Teilstruktur liegen trimere Einheiten [Ln3Cl12(H2O)6]3- vor, die entlang der c-Achse über den Ecken der hexagonalen Elementarzelle gestapelt sind. In der Stapelfolge sind die Einheiten um jeweils 60° zueinander verdreht. Die Koordinationszahl (C. N.) des Ln3+ ist 8 und setzt sich aus vier verbrückenden und zwei terminalen Chloridionen sowie zwei Wassermolekülen zusammen. Die C.N. der drei Rubidiumionen auf nicht symmetrieäquivalenten Lagen betragen 9, 8(+1) und 6(+6). Die thermische Entwässerung der Verbindungen erfolgt in einem Schritt bei ca. 100°C unter Zerfall in Rb2LnCl5 und RbCl, da die wasserfreien 3:1 Verbindungen Rb3LnCl6 erst ab ca. 400°C stabil sind.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210421
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  • 6
    Electronic Resource
    Electronic Resource
    Synthese und Kristallstrukturen der Phosphaniminato-Komplexe [SbF2(NPEt3)]2 und [SbF(NPEt3)2]2 sowie von NMe4+SbF4-Professor Lothar Beyer zum 60. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 2016-2022 
    Details
    ISSN: 0044-2313
    Keywords: Phosphoraneiminato Complexes of Antimony(III) ; Fluoro Complexes ; Crystal Structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structures of the Phosphoraneiminato Complexes [SbF2(NPEt3)]2 and [SbF(NPEt3)2]2 as well as of NMe4+SbF4-The title compounds have been prepared from antimony trifluoride with the silylated phosphaneimine Me3SiNPEt3 and [NMe4]F, respectively. They were characterized by IR spectroscopy and by crystal structure determinations.[SbF2(NPEt3)]2: Space group Pbca, Z = 8, structure determination with 1264 unique reflections, R1 = 0.028 for reflections with I 〉 2σ(I). Lattice dimensions at -80°C: a = 1284.8, b = 1162.4, c = 1380.4 pm. The compound forms centrosymmetric dimeric molecules, in which the Ψ-trigonal-bipyramidal coordinated antimony atoms are linked via μ2-N bridges of the NPEt3- ligands.[SbF(NPEt3)2]2: Space group P21/c, Z = 4, structure determination with 2270 unique reflections, R1 = 0.029 for reflections with I 〉 2μ(I). Lattice dimensions at -75°C: a = 815.8, b = 1121.2, c = 2068.5 pm, β = 101.09°. The compound forms centrosymmetric dimeric molecules, in which the Ψ-trigonal-bipyramidal coordinated antimony atoms are linked via μ2-N bridges of one of the two NPEt3- ligands. The other NPEt3- group is terminally connected.NMe4+SbF4-: Space group P21/c, Z = 4, structure determination with 1503 unique reflections, R1 = 0.069 for reflections with I 〉 2μ(I). Lattice dimensions at -50°C: a = 539.80, b = 896.10, c = 1760.3 pm, β = 90.338°. The compound includes monomeric SbF4- ions with distorted Ψ-trigonal-bipyramidal environment of the antimony atoms.
    Notes: Die Titelverbindungen entstehen durch Reaktion von Antimontrifluorid mit dem silylierten Phosphanimin Me3SiNPEt3 bzw. mit Tetramethylammonium-Fluorid. Sie werden IR-spektroskopisch und durch Kristallstrukturanalysen charakterisiert.[SbF2(NPEt3)]2: Raumgruppe Pbca, Z = 8, Strukturlösung mit 1264 unabhängigen Reflexen, R1 = 0,028 für Reflexe mit I 〉 2σ(I). Gitterkonstanten bei -80°C: a = 1284,8; b = 1162,4; c = 1380,4 pm. Die Verbindung bildet zentrosymmetrische dimere Moleküle, in denen die Ψ-trigonal-bipyramidal koordinierten Antimonatome über μ2-N-Brücken der NPEt3--Liganden verknüpft sind.[SbF(NPEt3)2]2: Raumgruppe P21/c, Z = 4, Strukturlösung mit 2270 unabhängigen Reflexen, R1 = 0,029 für Reflexe mit I 〉 2σ(I). Gitterkonstanten bei -75°C: a = 815,8; b = 1121,2; c = 2068,5 pm; β = 101,09°. Die Verbindung bildet zentrosymmetrische dimere Moleküle, in denen die Ψ-trigonal-bipyramidal koordinierten Antimonatome über μ2-N-Brücken eines der beiden NPEt3--Liganden verknüpft sind. Die zweite NPEt3--Gruppe ist terminal gebunden.NMe4+SbF4-: Raumgruppe P21/c, Z = 4, Strukturlösung mit 1503 unabhängigen Reflexen, R1 = 0,069 für Reflexe mit I 〉 2σ(I). Gitterkonstanten bei -50°C: a = 539,80; b = 896,10; c = 1760,3 pm; β = 90,338°. Die Verbindung enthält monomere SbF4--Ionen mit verzerrt Ψ-trigonal-bipyramidaler Umgebung der Antimonatome.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966221203
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