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  • 1
    Electronic Resource
    Electronic Resource
    Tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0): Preparation, Nucleophilic Addition Studies and Syntheses of cmplex Polycyclic Systems by Dianionic Oxy-Cope Rearrangement (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 182-190 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric syntheses ; chromium complexes ; diones ; oxy-Cope rearrangements ; polycycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tricarbonylchromium complex 3 of 1,2-dioxobenzocyclobutene (1) is easily prepared by hydrolysis of diacetal 4. Complex 3 stereoselectively undergoes both single and double nucleophilic addition reactions at the keto groups. As a consequence, addition of excess alkenyllithium to 3 gives rise to a dianionic oxy-Cope rearrangement yielding benzocyclooctenedione complexes with good diastereoselectivity. Trapping of the bis(enolate) intermediate with chlorotrimethylsilane gives bis(enolether) 23. Subsequent addition of two different alkenyllithium derivatives yields the asymmetrically substituted rearrangement product 15. To some extent, dependent on the method of hydrolysis, an intramolecular aldol addition follows the dianionic oxy-Cope rearrangement. This results in the formation of benzoanellated bicyclo[3.3.0]octane derivatives and, in the case of 1-cyclopentenyllithium as the alkenylmetal, in the tetraquinane system 19. The trans-anellation of one of the cyclopentane rings in trans-20 has been verified by an X-ray structural analysis. The highly substituted rearrangement product 21/22 is formed only in small yield; in solution the bis(enol) tautomeric form 22 is favored over diketone 21.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020210
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis, Characterization, and Some Reactions of the Tricarbonylchromium Complexes of 1,3-Indandione and Ninhydrin (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 167-179 
    Details
    ISSN: 1434-193X
    Keywords: 1,3-Indandione ; Ninhydrin ; Chromium complexes ; Acetals ; Oxidation ; Hetero Diels-Alder reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The syntheses and characterization of the tricarbonylchromium complexes of 1,3-indandione and ninhydrin are described. As the direct complexation proved unsuccessful, the acetal route was tried. Although some complexes were obtained, complex deacetalization did not work in the case of ninhydrin. Finally, the oxidation of tricarbonyl(η6-1,3-indandione)chromium(0) with dimethyldioxirane gave the ninhydrin complex in 75% yield in equilibrium with the indantrione complex. The latter reacts in hetero Diels-Alder reactions with dienes with diastereoselective formation of spiro anellated pyran derivatives.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Addition and Ring Expansion Reactions of Tricarbonyl(1,2-dioxobenzocyclobutene)chromium(0) with Carbon Nucleophiles - Unexpected Formation of Benzocycloheptene Derivatives and the First Head-to-Head Coupling of Two Methoxyallene Molecules (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2719-2727 
    Details
    ISSN: 1434-193X
    Keywords: Chromium ; Benzocyclobutene ; Dianionic Oxy-Cope Rearrangement ; Methoxyallene ; Benzocycloheptenedione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of carbon nucleophiles to (benzocyclobutenedione)tricarbonylchromium(0) (4) results in the formation of exo mono- and diadducts as well as 1,2-diketones as the consequence of proximal ring-opening reactions. In one case the unexpected formation of benzocycloheptenedione complexes is observed. Treatment of 4 with an excess of 1-ethoxy-1-lithioethene gives the product of a dianionic oxy-Cope rearrangement followed by an intramolecular aldol addition. This is also the case with lithiated methoxyallene, and as the result the first head-to-head coupling product 12 of two methoxyallene molecules is isolated in good yield. 12 is used as a diene in Diels-Alder cycloadditions, and its molecular structure is compared to that of the similar molecule 13, lacking the two exo methylene substitutents.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Diastereoselective Ring Expansion Rearrangements of (Benzocyclobutenone)-and (Benzocyclobutenedione)chromium Complexes: Syntheses of Substituted 1-Indanone and 1,3-Indandione Complexes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 823-835 
    Details
    ISSN: 1434-193X
    Keywords: (Arene)chromium complexes ; α-Ketol rearrangement ; Vinylcyclobutene-cyclohexadiene rearrangement ; Benzocyclobutenes ; Indanone derivatives ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Organolithium and Grignard reagents add to the oxo group of (benzocyclobutenone)tricarbonylchromium(0) (1) diastereoselectively from the exo face of the organic ligand. If acyl anion equivalents are used as nucleophiles, deprotection of the carbonyl functions of the adducts causes ring expansion reactions to occur. Among these a rare example of an anion-accelerated 1-vinylcyclobutenol-cyclohexadienol rearrangement is reported which results, after isomerization, in a naphthol complex. Other ring expansion reactions gave coordinated substituted indanone derivatives. The facial differentiation by the tricarbonylchromium moiety allows for the first time the determination of the distereoselectivity of these reactions. The 1-oxoindan-2-ol derivatives obtained can undergo an α-ketol rearrangement with formation of the corresponding 2-oxoindan-1-ol complexes. Some of these reactions were performed with nonracemic starting material in order to determine how far chirality transfer from the planar chiral starting material to C-2 in the indanone system was possible. The ring expansion was also feasible with the benzocyclobutenedione complex as a starting compound, the reaction giving substituted 1,3-indandione complexes. Crystal structure analyses of three of the complexes prepared are reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    η6-(1-oxobenzocyclobutene)tricarbonylchromium(0): Preparation, reduction, and ring-opening/cycloaddition chemistry of the 1-hydroxybenzocyclobutene complexDedicated to Professor Günther Wilke on the occasion of his 70th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 253-265 
    Details
    ISSN: 0947-3440
    Keywords: Bicyclo[4.2.0]octa-1,3,5-triene ; Chromium complexes ; [4+2] Cycloadditions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of the tricarbonylchromium complexes 2 and 3 of 1-oxobenzocyclobutene and 1-hydroxybenzocyclobutene are described. Alcoholate 6 of 3 undergoes a ring opening to the corresponding ortho-quinodimethane intermediate between -30 and -20°C, which is trapped by dienophiles with high diastereoselectivity. While with most dienophiles products with a 1,2-cis configuration (7, 8, 10) are formed, vinyl sulfones react in an exo-selective cycloaddition with formation of 1,2-trans-configurated cycloadducts (12, 13). The configuration of the cycloadduct with phenyl vinyl sulfone is confirmed by an X-ray crystal structure analysis. As one of the important aspects of the chemistry of benzocyclobutene complexes is the chirality of compounds like 2 and 3, the enantiomeric resolution has been achieved via the semioxamazones of ketone 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950235
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  • 6
    Electronic Resource
    Electronic Resource
    Reductive Coupling by Chromium(0) - (Bibenzyl)- and (Stilbene)tricarbonylchromium(0) Complexes by a One-Pot Reaction from Benzylic Halides (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 93-99 
    Details
    ISSN: 0009-2940
    Keywords: (Bibenzyl)tricarbonylchromium(O)/Reductive coupling by Cr(0)/(Stilben)tricarbonylchromium(O) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Cr(CO)3(NH3)3 with benzylic mono-, di-, and trihalides leads to the formation of 1,2-diarylethanes, -ethenes, and diphenylethyne in satisfactory yields. Di(halomethyl)benzene derivatives yield product mixtures containing both reduction products and coupling products. With a higher excess in chromium(O), under otherwise unchanged reaction conditions, the corresponding (arene)tricarbonylchromium(O) complexes of the coupling products are formed in a one-pot reaction from the benzylic halides.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230120
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  • 7
    Electronic Resource
    Electronic Resource
    Chemie (1995)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 29 (1995), S. IX 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19950290514
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  • 8
    Electronic Resource
    Electronic Resource
    The Synthesis of 4,7-Bis(dialkylamino)tricyclo[5.2.1.04,10]deca-1(10),2,5,8-tetraenes and their Reduction with Alkali Metal (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1658-1669 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of the novel 4,7-bis(dialkylamino)tricyclo[5.2.1.04,10]deca-1(10), 2,5,8-tetraenes 12 from 1,4,7-trihalotriquinacenes 8 and secondary amines is reported. The structural and electronic characteristics of these as well as the acepentalene dianion (32-) and some related systems as determined by semiempirical (MNDO) calculations are discussed. Thereby, 32- should be a triply etheno-bridged trimethylenemethane dianion exhibiting Y-delocalization favored over the formation of a peripheral 10π-electronic system. Attempts directed towards the generation of 32- by reacting tetraenes 12 with Na led to the formation of tris(dialkylamino)triquinacenes 9, presumably by a kind of reduction/disproportionation mechanism.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680620
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  • 9
    Electronic Resource
    Electronic Resource
    η4-Complexes of 4,7-Dihydroacepentalene: Facile Degenerate Haptotropic Rearrangement of (η5-Cyclopentadienyl)(η4-4,7-dihydroacepentalene)cobalt(I) in Contrast to its Tricarbonyliron Counterpart (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2423-2427 
    Details
    ISSN: 0009-2940
    Keywords: Acepentalene ; 4,7-dihydro ; complexes ; Degenerate haptotropic rearrangement ; Cobalt complexes ; Iron complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (cyclopentadienyl)cobalt(I) complex 4 of the 4,7-dihydroacepentaleneThe numbering of the ring system corresponds to the tricyclo-decatetraene nomenclature used in the Exp. Part. Thus, 4,7-substitution would be 2a,4a-substitution in acepentalene numbering. derivative 2b has been prepared by the reaction of the ligand with (cyclopentadienyl)bis(ethene)cobalt(I). NOE experiments indicate a complexation at the convex face of the polyolefinic ligand. 1H-NMR spectra establish a degenerate haptotropic rearrangement with CpCo migration from one diene unit to the adjacent one. The activation energy of this process is estimated to be 15 kcal/mol. An X-ray crystal structure determination of (η4-4,7-dihydroacepentalene)tricarbonyliron derivative 3a shows a distorted coordination of Fe(CO)3 at the convex face of the ligand, too.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241108
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  • 10
    Electronic Resource
    Electronic Resource
    [ω-(Phosphanyl)alkyl]cyclopentadienyl ComplexesDedicated to Professor Carl Krüger on the occasion of his 60th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1657-1669 
    Details
    ISSN: 0009-2940
    Keywords: Anions, [ω-(phosphanyl)alkyl]cyclopentadienyl ; Cobalt, [ω-(phosphanyl)alkyl]cyclopentadienyl complexes ; Cobalt(I) chelate complexes ; Iron, [ω-(phosphanyl)alkyl]cyclopentadienyl complexes ; Zirconium, [ω-(phosphanyl)alkyl]cyclopentadienyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses and characterisation of the [ω-(phosphanyl)alkyl]cyclopentadienyl anions 2, 3, 6-8, 10, and 11 are described. These anions form metallocenes 12-15 and 17-19 with FeCl2 · 2 THF and with ZrCl4 · 2 THF, respectively. With ICo(CO)4 chelated carbonbyl complexes 23-25, 28, and 29 are formed. The unchelated intermediate 20 has been detected by IR spectroscopy. The carbonyl chelate complexes are thermally stable. Under photochemical conditions, ligand exchange reactions are possible which in the case of 1,5-cyclooctadiene proceed with decomplexation of the phosphane arm. This does not prevent a reaction at the cobalt(I) atom; treatment of 35 with diphenylethyne gives the corresponding tetraphenylcyclobutadiene complex 36 in good yield, the phosphane arm remaining uncoordinated.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260725
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