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  • 1
    Electronic Resource
    Electronic Resource
    Darstellung, chiroptische eigenschaften und absolute Konfiguration von 4,14-disubstituierten [2.2]Metacyclophanen (1976)
    Springer
    Monatshefte für Chemie 107 (1976), S. 195-208 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Resolution of [2.2]metacyclophane-4,14-dicarboxylic acid (2) was achieved by crystallization of its (+)- and (−)-α-phenylethylamine salts. Chemical correlation with (−)-(S)p-[2.2]metacyclophane-4-caboxylic acid (−)-11 via its monobromo derivative (−)-8 established the absolute configuration of the dicarboxylic acid as (−)-(S)p-2. The key compound (−)-8 was prepared by partial lithiation and subsequent carboxylation of 4,14-dibromo[2.2]metacyclophane (1) and resolution with (−)-phenylethylamine. Recently proposed rules correlating the absolute configurations of planarchiral compounds with theirCD-spectra are discussed and a comparison of the chiroptical properties of 4,14-di- and 4-mono-substituted [2.2]metacyclophanes is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00909095
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  • 2
    Electronic Resource
    Electronic Resource
    Zum rotameren Verhalten des Phenyl- und Phenyltricarbonylchrom-liganden in 2-substituierten 1,3-Dioxanen: Ein Vergleich (1977)
    Springer
    Monatshefte für Chemie 108 (1977), S. 113-122 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dipole moment measurements, NMR-spectroscopical methods and dipole-dipole interaction calculations applied to 2-benchrotrenyl-1,3-dioxanes and a comparison with o-substituted 2-phenyl derivatives furnish evidence, that in both cases the rotameric state is mainly determined by the steric demand of the substituent being attached to phenyl: the declination angle (π) of the Cr(CO)3-group from the bisectional cisoid relation (with respect to H on C-2) is identical with that for the ortho substituent and amounts to about 60 degs. The influence of the Cr(CO)3-fragment on the conformational behaviour of the benzene moiety in geminal 2,2-disubstituted derivatives is consistent with these results: the assumption of an axial and gonal conformation for the phenyl ring, which had recently been established for 2-alkyl-2-phenyl-1,3-dioxanes, is no longer valid for the 2-alkyl-2-phenyltricarbonylchromium compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900913
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  • 3
    Electronic Resource
    Electronic Resource
    Stereochemie von Metallocenen, 40. Mitt. (1977)
    Springer
    Monatshefte für Chemie 108 (1977), S. 767-780 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Starting from optically active methylferrocene-α- and-β-carboxylic acids (1 a and1 b) of known absolute configuration and enantiomeric purity about 15 chiral ferrocenes (of each isomeric series—α and β) were obtained by suitable ligand transformations. Thereby (almost) all possible chiral combinations of the ligands CH3, COOH (COO−), COOCH3, C≡N and NH2 (NH3 +) were accessible which are necessary for a potential test of approximations of chirality functions for compounds with basic symmetry C5v. The chiroptical properties of these disubstituted ferrocenes are recorded. Preliminary tests using a shortened Ansatz revealed large discrepancies between calculated (χ) and found [M]D-values. Possible reasons for this failure are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00898040
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  • 4
    Electronic Resource
    Electronic Resource
    Syntheses and stereochemistry of metalloceno cycloocta-1,5-dienes: [2]Orthocyclo[2](1,2)benchrotrenophane and-ferrocenophane, [2.2](1,2)Ferrocenophane (1978)
    Springer
    Monatshefte für Chemie 109 (1978), S. 805-822 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die im Titel genannten Verbindungen2, 3 und4 wurden im Hinblick auf die Untersuchung ihrer Konfiguration und Konformation — vor allem im Vergleich mit Cyclophanen verwandter Struktur, wie [2.2]Orthocyclophan (1) — dargestellt. Während das Benchrotrenderivat2 in einem Schritt aus1 und Cr(CO)6 zugänglich war, wurden die Ferrocenophane3 und4 ausgehend von einer Wittigreaktion schrittweise aufgebaut: Dabei erhielt man hydroxymethylierte Ferrocenyl-phenyl- und Diferrocenyl-ethylene, in denen — nach Hydrierung zu den entsprechenden Ethanen — die CH2OH-Gruppen in Essigsäurereste umgewandelt wurden. Anschließender Ringschluß und Reduktion der cyclischen Ketone19 und33 lieferten die gewünschten Phane, von denen das Diferrocenoderivat4 als 3:1-Mischung dertrans- undcis-Isomerena bzw.b erhalten wurde. Die konfigurative Zuordnung erfolgte vor allem auf Grund der1H-NMR-Spektren. Die konformativen Möglichkeiten — vor allem von4 — werden kurz diskutiert und vorläufige Konformationen für die Stereoisomeren von4 vorgeschlagen.
    Notes: Abstract The title compounds2, 3, and4 have been prepared for configurational and conformational studies—mainly in comparison with cyclophanes of related structures, such as [2.2]orthocyclophane (1). Whereas the benchrotreno derivative2 was accessible in one step from1 and Cr(CO)6, the ferrocenophanes3 and4 were prepared by a stepwise reaction sequence starting with a Wittig reaction: thereby hydroxymethylated ferrocenyl phenyl and diferrocenyl ethylenes were obtained in which (after hydrogenation to the corresponding ethanes) the CH2OH groups were transformed into acetic acid residues. Subsequent ringclosure and reduction of the cyclic ketones19 and33 afforded the desired phanes, of which the diferroceno derivative4 was obtained as a 3∶1 mixture of thetrans andcis isomersa andb, resp. The configurational assignment was based mainly on the1H-nmr spectra. Conformational possibilities especially of4 are briefly discussed and tentative conformations are assigned to the stereoisomers of4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00907301
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  • 5
    Electronic Resource
    Electronic Resource
    Optisch aktive aromatische Spirane, 7. Mitt. Circulardichroismus optisch aktiver 5,5′-disubstituierter 2,2′-Spirobiindane (1978)
    Springer
    Monatshefte für Chemie 109 (1978), S. 987-999 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dipole-dipole coupling of the indane fragments in 5,5′-disubstituted 2,2′-spirobiindanes is predominantly responsible for the origin of optical activity in the1La-electronic transition only if both ligands exhibit strong interaction with the aromatic nuclei. This mechanism does not contribute essentially to the1Lb-Cotton effect. The band-splittings of the couplet as well as the rotational strengths of the transitions ofA andB symmetry-type in the1La-Cotton effect are in accordance with a rough calculatory estimation. The absolute configuration thus determined agrees with the chirality recently deduced by chemical methods. The rotational strengths of the1W-Cotton effect of the carbonyl derivatives4, 5, 12, 13, and15 located at appr. 320 nm are remarkably low. This can be explained on the basis of conformational considerations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00907320
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  • 6
    Electronic Resource
    Electronic Resource
    Stereochemie von Metallocenen, 42. Mitt.: Optisch aktives π-Fluorenon-tricarbonylchrom — Darstellung, enantiomere REinheit, absolute Konfiguration und Versuche zur Racemisierung (1978)
    Springer
    Monatshefte für Chemie 109 (1978), S. 1227-1240 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Racemic Fluorenone-Cr(CO)3 (1) was prepared from fluorenone ethyleneketal by complexation with Cr(CO)6 and subsequent cleavage of the dioxolane9. Asymmetric reduction of1 with a chiral Lithium hydride afforded both (+)-1 and the correspondingendo-carbinol (−)-7 a with optical yields up to 80% as established by the use of chiral nmr shiftreagents. Active1 could also be obtained by two other asymmetric reactions albeit with low optical yields. LiAlH4−AlCl3 reduction of (+)-1 gave traces of (+)-fluorene-Cr(CO)3 (2). The absolute chirality of (+)-1 was deduced as (S) by application of the abovementioned asymmetric reduction to ferroceno indenone (11) of known configuration and byHoreau's method to (−)-7 a. Several attempts to racemize1 failed, which proves that no transanular shift of Cr(CO)3 takes place. The CD spectra of1 and2 are reported. Some side reactions such as the reduction of7 a to2 with Cr(CO)6 in dibutylether (leading also to the formation of isomeric dimethylbenchrotrenes from the solvent) and the formation of a binuclear complex14 between1 and2 are briefly reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00913024
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  • 7
    Electronic Resource
    Electronic Resource
    The absolute chirality of (+)-12-Bromo-[2.2]metacyclophane-4-carbonitrile (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 511-516 
    Details
    ISSN: 1434-4475
    Keywords: Bijvoet X-ray diffraction method ; Circular dichroism ; Exciton model ; Kinetic resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die absolute Konfiguration von (+)-12-Brom-[2.2]metacyclophan-4-carbonitril [(+)-4 e] wurde mit Hilfe der anomalen Röntgenbeugung (Bijvoet-Methode) als(R) p (Fig. 1) ermittelt. Damit sind auch die Konfigurationen aller optisch aktiven 4-monosubstituierten, 4,14-homodisubstituierten sowie der 4,12- und 4,14-heterodisubstituierten [2.2]Metacyclophane bekannt, die mit (+)-4 e eindeutig chemisch korreliert sind. Dieses Ergebnis wird mit jenen verglichen, die mit Hilfe anderer Methoden zur Konfigurationsermittlung erhalten wurden.
    Notes: Abstract The absolute configuration of (+)-12-bromo-[2.2]metacyclophane-4-carbonitril [(+)-4 e] was determined by theBijvoet X-ray diffraction method as(R) p (Fig. 1). This result allows the unambigous assignment of the absolute chiralities of all optically active 4-monosubstituted, 4,14-homodisubstituted, 4,12- and 4,14-heterodisubstituted [2.2]metacyclophanes chemically correlated with (+)-4 e. The result is compared with those obtained by other methods for establishing the absolute configuration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00901830
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  • 8
    Electronic Resource
    Electronic Resource
    Optisch aktive, aromatische Spirane, 8. Mitt.: Darstellung optisch aktiver, 5, 5′, 6′-trisubstituierter 2,2′-Spirobiindane bekannter Chiralität und enantiomerer Reinheit (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 541-565 
    Details
    ISSN: 1434-4475
    Keywords: Configurational correlation ; 5-Ethylindanes ; 1 H-nmr spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Starting from (+) (2R) methyl 5′-ethyl-2,2′-spirobiindane-5-carboxylate of known enantiomeric purity 79 optically active, configurationally correlated 5,5′,6′-trisubstituted 2,2′-spirobiindanes (2–7) were prepared for the purpose of testing a “shortened polynomal Ansatz” for chirality functions. Their optical rotations and1H-nmr spectra are reported. In this context several 6-substituted 5-ethylindanes (1) were prepared as model compounds for synthetic transformations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938359
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  • 9
    Electronic Resource
    Electronic Resource
    Stereochemie von Metallocenen, 43. Mitt.: Torsionsisomere Biphenyl-tricarbonylchrom-Komplexe: Darstellung, Konformationsanalyse und Kinetik der Interkonversion (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 437-451 
    Details
    ISSN: 1434-4475
    Keywords: Conformational analysis ; Lanthanide induced shift ; NMR, coalescence ; Optical activity ; Rotational barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Complexation of methyl 3-nitro-2-(o-tolyl)-benzoate (2, ano-trisubstituted biphenyl) with hexacarbonyl chromium gave the isomeric Cr(CO)3 complexes3 and4 both existing as two torsional isomersa andb, as seen by nmr. For the main product3 the preferred conformations of the two torsional isomersa andb were deduced by the lanthanide induced shift (LIS) technique. The activation energy for the interconversion process could be determined from kinetic measurements and especially from1H-nmr coalescence temperature of the methylsignals. The barrier of 91±1.5 kJ/mol (21.7±0.3 kcal/mol) in3 reflects the interaction of theo-H-atom of the benzene ring passing the Cr(CO)3 moiety of the benchrotrene ring during the interconversion. A partial optical resolution of3 was achieved by asymmetric reduction with a chiral lithium-aluminium hydride yielding (+)-3 with [α] D 20 +30° (benzene) and the levorotatory alcohol (−)-7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00911932
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  • 10
    Electronic Resource
    Electronic Resource
    Optisch aktive, aromatische Spirane, 11. Mitt.: Synthese optisch aktiver mono- bis heptasubstituierter 5-Methyl- und 5-Ethyl-2,2′-spirobiindane und analoger Naphthalinderivate bekannter Chiralität und enantiomerer Reinheit (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 801-823 
    Details
    ISSN: 1434-4475
    Keywords: Chirality function ; Circular dichroism ; Ligand parameters ; 5-Methyl and ethylindanes ; 1H-NMR spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Starting from optically active 5,5′-dimethyl, diethyl, and 5-ethyl-5′-methyl-2,2′-spirobiindane as well as from 5′-ethyl-spirobiindane-5-carboxylic ester of known enantiomeric purity and configuration 75 mono to polysubstituted 2,2′-spirobiindanes have been prepared. Amongst these are several compounds with rings anellated in the 6,7 (and 6′, 7′) positions, especially a spirohydrocarbon4 x with orthogonal naphthalene units the circular dichroism of which is reported and discussed. Several mono and disubstituted 5-methyl and ethylindanes (1,2) have been prepared as models for synthetic transformations in the spirobiindane series. From the molar rotations of symmetrically diacylated 5,5′-dimethyl and diethyl spirobiindanes (4a, 7b, 7c) empirical ligand parameters λ for acetyl and methoxycarbonyl were determined which gave much better results in the calculation of the rotations of appropriate spirobiindanes (with the “shortened polynomal Ansatz”) than the λ-values deduced previously from 5,5′-disubstituted spirobiindanes. The significance of these results is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899783
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