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  • Organic Chemistry  (3)
  • Syntheses  (2)
  • 1995-1999  (5)
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Reactions of 3,5-Diaryl-1,2-dithiolium Salts and 3,5-Diaryl-1,2,4-dithiazolium Salts with Metal Cyclopentadienides (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 221-228 
    Details
    ISSN: 0947-3440
    Keywords: 3,5-Diaryl-1,2-dithiolium salts ; 3,5-Diaryl-1,2,4-dithiazolium salts ; Metal cyclopentadienides ; 3,7-Dithiatricyclo[4.4.0.02,8]deca-4,9-diene ; 3,5-Dithiatricyclo[4.2.2.02,6]deca-7,9-diene ; 3,7-Dithia-5-azatricyclo[4.4.0.02,8]deca-4,9-diene ; Diels-Alder reactions ; Nitrogen heterocycles ; Sulfur heterocycles ; Polycycles ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of the 3,5-diaryl-1,2-dithiolium salts 2 with the metal cyclopentadienides 4 and 9 leads to the formation of the tricyclic compounds 6 and 10 via a ring-opened intermediate, which undergoes an intramolecular Diels-Alder cyclization. Compounds 6 and 10 rearrange by treatment with boron trifluoride-diethyl ether to the isomeric compounds 7 and 11. The structures 6f and 7f were confirmed by X-ray analysis. Condensation of the 3,5-diaryl-1,2,4-dithiazolium salts 3 with the metal cyclopentadienides 4 affords the tricyclic compounds 12, which do not rearrange by Lewis acid catalysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970133
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  • 3
    Electronic Resource
    Electronic Resource
    A Novel Cycloocta[d]-/Barreleno[d]pyridazine RearrangementDedicated to Prof. Dr. Dr. h.c. F. Eiden on the occasion of his 70th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 661-666 
    Details
    ISSN: 0947-3440
    Keywords: Cyclooctatetraene-bicyclooctatriene valence tautomerism ; [4+2] Cycloadditions, inverse ; Cycloocta[d]pyridazine ⇛ barreleno[d]pyridazine rearrangement ; [1, 3]-Carbon migration ; Catalysis, 1,3-tautomerization with 2-hydroxypyridine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of the valence tautomeric system cyclooctatetraene (2) bicyclo[4.2.0]octa-2,4,7-triene (3), the monocyclic polyene (2) reacts as a dienophile with the diazadiene 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine (1) to form after N2-elimination two products: The 1 : 1-adduct 6, a cycloocta[d]pyridazine, and the tetracyclic bis-Diels-Alder cycloadduct 9. Depending on solvent polarity and temperature, compound 6 displays interesting novel rearrangements. On refluxing in nonpolar solvents like toluene, compound 6 yields the barreleno[d]pyridazine 13 in high yield. Compound 13 can be oxidized with 4-phenyltriazolinedione 14 to the barreleno[d]pyridazine 15. When the more polar nitromethane is used as a solvent, heating of 6 at 90° 2°C surprisingly leads to the dihydrocycloocta[d]pyridazine 18 in a multistep reaction including proton-shift tautomerism and [1, 5]-sigmatropic rearrangement. The structures of the compounds 15 and 18 were assigned by the spectral data and verified by X-ray crystallography.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950493
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  • 4
    Electronic Resource
    Electronic Resource
    Manganorganische Phosphaniminato-Komplexe mit HeterocubanstrukturProfessor Rainer Mattes zum 60. Geburtstag gewidmet (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 351-356 
    Details
    ISSN: 0044-2313
    Keywords: Organomanganese Compounds ; Phosphoraneiminato Complexes ; Syntheses ; Crystal Structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organomanganese Phosphoraneiminato Complexes with Heterocubane StructureThe organomanganese phosphoraneiminato complexes [MnR(NPEt3)]4 (R = Me, C=C—Ph, C=C—Tol, C=C—CMe3, C=C—SiMe3) with heterocubane structures have been prepared by reaction of the bromo derivative [MnBr(NPEt3)]4 with the corresponding lithium reagents LiR in THF/hexane solution, forming shiny red, very reactive compounds which are well soluble in hydrocarbons. They were characterized by mass spectroscopy, IR spectroscopy and by crystal structure determinations. According to these the compounds form nearly perfect Mn4N4 heterocubane frameworks with m̈3-N bridges of the phosphoraneiminato groups with Mn—N bond lengths of 214.5 pm in average which leads to Mn … Mn contacts of 299.5 pm in average. The organic residues R are terminal bonded with Mn—C distances Mn—Me of 219.5 pm and Mn—C=C—R of 207.6 pm in average.
    Notes: Die organisch substituierten Phosphanimi nato-Komplexe des Mangan(II) mit Heterocubanstruktur [MnR(NPEt3)]4 (R = Me, C=C—Ph, C=C—Tol, C=C—CMe3, C=C—SiMe3) werden durch Reaktion des Bromoderivates [MnBr(NPEt3)]4 mit den entsprechenden Lithium-Reagentien LiR in THF/Hexan als leuchtend rote, sehr reaktive, in Kohlenwasserstoffen leicht lösliche Verbindungen erhalten. Sie werden durch die Massen- und IR-Spektren sowie durch Kristallstrukturanalysen charakterisiert. Danach werden je vier Manganatome über je vier m̈3-N-Atome der Phosphan-iminato-Gruppen zu nur wenig verzerrten m̈3-N4-Kuben mit Mn—N-Abständen von im Mittel 214,5 pm verbrückt, was zu Mn … Mn-Kontakten von 299,5 pm führt. Die Reste R sind terminal gebunden mit Mn—C-Abständen Mn—Me von 219,5 pm und Mn—C=C—R von im Mittel 207,6 pm.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230156
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  • 5
    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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