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  • Circular dichroism  (10)
  • Configurational correlation  (4)
  • 1,3-Diferrocenylpropenes  (1)
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Optisch aktive aromatische Spirane, 13. Mitt. (1985)
    Springer
    Monatshefte für Chemie 116 (1985), S. 789-799 
    Details
    ISSN: 1434-4475
    Keywords: Chirality function ; Chromatographic resolution ; Circular dichroism ; Configurational correlation ; Ligand parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several optically active title compounds were obtained from the 4′-acetyl-4-carboxylic acid2 or the 4,4′-diacetyl derivative4. (−)-2 was accessible by optical resolutionvia its (−)-α-phenethylamine salts, (+)- and (−)-4 as well as the enantiomeric methylesters3 (of2) were obtained by chromatography on triacetylcellulose in ethanol. The enantiomeric purities were established either from the chromatographic results or from the1H-NMR spectra of the phenethyl-amine saltes (via the diastereotopic acetyl protons). The chirality (−)-(2R) was deduced for all new compounds from a chemical correlation between (−)-2 and (−)-4 and on the basis of the CD spectra of the latter and of (−)-(2R)-17 of known absolute configuration. From the molar rotations of these 4,4′-disubstituted 2,2′-spirobiindanes (empirical) ligand parameters λ were determined which for some cases gave good results in the calculation of the rotations (using the “shortened Ansatz”). These results are briefly discussed especially in comparison with 5,5′-disubstituted 2,2′-spirobiindanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809156
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  • 3
    Electronic Resource
    Electronic Resource
    Stereochemistry of planarchiral compounds, part XII: Absolute chiralities and X-ray crystal structures of 2,2′-Bi(1,6-methano[10]annulenyl)s (1989)
    Springer
    Monatshefte für Chemie 120 (1989), S. 453-462 
    Details
    ISSN: 1434-4475
    Keywords: Bijvoet method, Chemical and chiroptical correlation ; Circular dichroism ; Enantioselective chromatography ; 10,10′-Dibromo-2,2′-bi(1,6-methano[10]annulenyl) ; Torsional isomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die absolute Chiralität des rechtsdrehenden (als Hauptmenge im Gemisch vorliegenden) Rotamers von 10,10′-Dibrom-2,2′-bi(1,6-methano[10]annulenyl) (1 b) (erhältlich durch Tieftemperatur-Chromatographie oder Kristallisation des (+)-Enantiomers von1 b) wurde durch Röntgenstrukturanalyse (Bijvoet-Methode) als (+)-(R) p (R) a (R) p ermittelt. Dieses Ergebnis konnte durch Reduktion von (+)-1 b bestätigt werden: Sie führte zu einem rechtsdrehenden 2,2′-Bi(1,6-methano[10]annulenyl) (1 a), das seinerseits durch Kupplung von (−)-2-Brom-1,6-methano[10]annulen (3) bekannter Chiralität (S) p erhalten wurde (und auch durch enantioselektive Chromatographie von1 a an Triacetylcellulose in Ethanol zugänglich ist). Diese Korrelation legt auch die Chiralität des (+)-Enantiomers von racem.1 a als (S) p (S) p fest. Nach den Röntgenstrukturanalysen des (Haupt)-Rotationsisomers von (+)-1 b und der Mesoform (2 b) liegen im Kristall Konformere vor, in denen die Bromatome den CH2-Brücken nahekommen. Die Torsionswinkel um die 2,2′-Bindung variieren von 33° über 53° bis 65° für (+)-1 b, racem.1 b und meso2 b.
    Notes: Summary The absolute chirality of the dextrorotatory main rotamer of 10,10′-dibromo-2,2′-bi(1,6-methano[10]annulenyl) (1 b), obtained by low temperature chromatography or by crystallisation of the (+)-enantiomer of1 b, was established by observation of anomalous X-ray diffraction as (+)-(R) p (R) a (R) p -1b. This result was confirmed by reduction of (+)-1 b to a dextrorotatory 2,2′-bi(1,6-methano[10]annulenyl) (1 a), which in turn was accessible by coupling of (−)-2-Bromo-1,6-methano[10]annulene (3) of known chirality (S) p and, moreover, by enantioselective chromatography of1 a on triacetyl cellulose in ethanol. This correlation determines also the chirality of (+)-1 a as (S) p (S) p . According to the X-ray analyses the main rotamer of (+)-1 b and the meso-form (2 b) adopt crystal structures in which the bromine atoms come close to the CH2-bridges. The torsional angles around the 2,2′-bonds vary between 33°, 53° and 65° for (+)-1 b, racem.1 b and the mesoform2 b, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811557
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  • 4
    Electronic Resource
    Electronic Resource
    Chirality due to deuterium substitution: synthesis and circular dichroism of (+)(R) p -2,7-dideuterio-1,6-methano[10]annulene (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 465-467 
    Details
    ISSN: 1434-4475
    Keywords: Enantioselective chromatography ; Planar chirality ; Circular dichroism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Titelverbindung wurde aus (−)(S) p -2,7-Dibrom-1,6-methano[10]annulen durch Umsetzung mitn-Bu-Li und nachfolgende Reaktion mit D2O dargestellt. Optische Rotationen bei vier Wellenlängen und das Circulardichroismus-Spektrum wurden bestimmt.
    Notes: Summary The title compound was prepared from (−)(S) p -2,7-dibromo-1,6-methano[10]annulene by treatment withn-Bu-Li and subsequent quenching with D2O. The optical rotations at four wavelengths and the circular dichroism spectrum are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00817603
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  • 5
    Electronic Resource
    Electronic Resource
    Stereochemistry of planarchiral compounds, part X (1986)
    Springer
    Monatshefte für Chemie 117 (1986), S. 255-267 
    Details
    ISSN: 1434-4475
    Keywords: Bijvoet method ; Circular dichroism ; Chemical and chiroptical correlation ; Configurational stability ; [10]Anulene, 2-Bromo- and 2,7-dibromo-1,6-methano- and 2,7-dibromo-1,6-oxido- and 1,6-imino- ; 2,9-Dibromo-syn-1,6:8,13-diimino- and dioxido[14]anulene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung 2,7-Dibrom-1,6-methano[10]anulen (3) und 2,9-Dibrom-syn-1,6:8,13-diimino[14]anulen (9) wurden durch Chromatographie an Triacetylcellulose (TAC) in Ethanol quantitativ in ihre Enantiomeren getrennt. Röntgenstruktur-analyse (Bijvoet-Technik) bewies für die rechtsdrehenden Enantiomeren die Chiralität (+)(R)-3 bzw. (+)(S)-9. Ein Vergleich der CD-Spektren ermöglichte die Konfigurationszuordnung weiterer optisch aktiver [10]- und [14]Anulene, die gleichfalls durch Chromato-graphie anTAC erhalten worden waren. Umwandlung von (+)(R)-2-Brom-1,6-methano[10]anulen (2) in den entsprechenden Methylester (−)-4 bestätigte dessen schon früher vorgeschlagene Chiralität (−)(R). Dibrom-1,6-oxido[10]anulen (7) und Dibrom-diimino[14]anulen (9) sind im Gegensatz zum Dioxido[14]anulen (10) bis 250°C optisch stabil. Ihre Inver-sionsbarrieren liegen somit über ∼ 42 kcal (176kJ) mol−1. Die CD-Spektren von mono- und disubstituierten Anulenen (mit C1 bzw. C2-Symmetrie) werden verglichen: Für die [10]Anulene scheint derCottoneffekt um 330 nm konfigurationsspezifisch zu sein, wobei ein positiver Effekt (S)-Chiralität anzeigt — und vice versa. Einige Regelmäßigkeiten bezüglich der chromatographischen Enantiomerentrennung werden diskutiert.
    Notes: Abstract 2,7-Dibromo-1,6-methano[10]anulene (3) and 2,9-Dibromo-syn-1,6:8,13-diimino[14]anulene (9) were quantitatively separated into their enantiomers by chromatography on triacetylcellulose (TAC) in ethanol. X-ray structure analysis (Bijvoet technique) established the chiralities (+)(R)-3 and (+)(S)-9 for the dextrorotatory enantiomers. Comparison of the CD spectra allowed the configurational assignment to further optically active [10] and [14] anulenes which were also accessible by chromatography onTAC. Conversion of (+)(R)-2-bromo-1,6-methano[10]anulene (2) into the corresponding methylester (−)-4 confirmed its previously proposed chirality (−)(R). 2,7-Dibromo-1,6-oxido[10]anulene (7) and 2,9-dibromo-syn-diimino[14]anulene (9) are in contrast to the 2,9-dibromo-syn-dioxido[14]anulene (10) optically stable until 250°C. Consequently their inversion barriers are higher than ∼ 42 kcal (176 kJ) mol−1. The CD spectra of mono and disubstituted anulenes (with C1 and C2 symmetry, resp.) are compared: For the [10]anulenes theCotton effect around 330 nm seems to be specific for their configuration with a positive effect indicating (S)-chirality and vice versa. Some regularities concerning the chromatographic resolutions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809445
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  • 6
    Electronic Resource
    Electronic Resource
    Static and dynamic stereochemistry of 1,1′-bi(9,10-dihydro-9,10-ethano-anthryl) (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 1097-1108 
    Details
    ISSN: 1434-4475
    Keywords: Circular dichroism ; Chemical and chiroptical correlation ; Enantioselective chromatography ; Torsional isomers and barriers ; X-ray crystal structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Titelverbindung2 wurde durch Hochdruckreaktion von 1,1′-Bianthryl mit Ethylen oder durch Kupplung von 1-Brom-9,10-dihydro-9,10-ethano-anthracen (4) als Mischung der Diastereomeren (Mesoform2a und Racemat2b) im Verhältnis von 1.5:1 bzw. 2.3:1 erhalten. Die konfigurative Zuordnung erfolgte sowohl aus den1H- und13C-NMR-Spektren als auch durch Kupplung von linksdrehendem4 zu (−)-2 b. Optisch aktives4 war durch enantioselektive Chromatographie an Triacetylcellulose in Ethanol optisch rein zugänglich. Seine Konfiguration wurde durch Umwandlung in die entsprechende Carbonsäure5 (bekannter Chiralität) als (+)(9R) [bzw. (−)(9S)] bestimmt. Damit war auch die Zentrochiralität im erwähnten Kupplungsprodukt (−)-(2b) als (9S)(9′S) festgelegt. Das Racemat2b ist eine Mischung von Rotameren im Verhältnis von 1.8:1. Die Rotationsbarriere wurde (in Abhängigkeit von der Temperatur) als ΔG#=92−95 kJ mol−1 sowohl durch1H-NMR-als auch CD-Kinetik (basierend auf der Äquilibrierung der getrennten optisch aktiven Rotameren vonracem.2) ermittelt. Für die letzteren können aufgrund der Annahme bevorzugter Konformationen auch die Symbole für die Axialchiralität vorgeschlagen werden. Für (−)-2b: (9S)(R)a(9′S) für das überpopulierte bzw. (−)-(9S)(S)a(9′S) für das unterpopulierte Rotamer. Diese Annahmen wurden durch Röntgenstrukturanalysen von2a und des Hauptrotamers von2b (mit Torsionswinkeln von −111.1 bzw. −121.2°) bestätigt.
    Notes: Summary The title compound2 was prepared either by highpressure reaction of 1,1′-bianthryl with ethylene or by coupling of 1-bromo-9,10-dihydro-9,10-ethanoanthracene (4). Both syntheses afforded a mixture of diastereoisomers (meso2a and racemate2b) in a ratio of 1.5:1 and 2.3:1, respectively. Configurational assignment was possible both from the1H- and13C-NMR spectra and by coupling of laevorotatory4 (accessibly by enantioselective chromatography on triacetyl cellulose in ethanol) to laevorotatory2b. (+)-4 was tranformed into the dextrorotatory carboxylic acid (+)-5 of known configuration (9R) thus establishing the configuration of (+)-4 as (9R) too and hence the centrochirality in (−)-2b as (9S)(9′S). The racemic form2b is a conformational (appr. 1.8:1) mixture of two rotamers. The rotational barrier was established as ΔG #=92−95 kJ mol−1 (depending on the temperature) both by1H-NMR and CD kinetics (based on equilibration of the separated optically active rotamers ofracem.2). For the latter preferred conformations were assumed allowing the assignment of the axial chirality: e.g. (−)-(9S)(R)a(9′S) for the main rotamer of (−)-2 b [and (−)(9S)(S)a(9′S) for the underpopulated one]. All assumptions were confirmed by X-ray crystal structure analyses of2 a and the main rotamer of2b with torsional angles around the 1,1′-bonds of −111.1 and −121.2°, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811118
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  • 7
    Electronic Resource
    Electronic Resource
    Chiral crystals of “meso”-1,1′-bi(9,10-dihydro-9,10-ethano-anthryl). Chiroptical properties, absolute chirality and rotational barrier (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 1211-1215 
    Details
    ISSN: 1434-4475
    Keywords: Vapour diffusion method ; Circular dichroism ; Configurational correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Optisch aktive Kristalle von „meso“-1,1′-Bi(9,10-dihydro-9,10-ethano-anthryl) (1a) wurden aus Chloroform/Hexan mit Hilfe der Dampfdiffusionsmethode erhalten (orthorhombische Raumgruppe P212121). Die chiroptischen Eigenschaften von1a wurden in CH2Cl2 bei 0° und 10 °C gemessen: [α]D=−90°. Die absolute Chiralität (−)(R) a konnte mit hoher Wahrscheinlichkeit durch chiroptischen Vergleich (über die CD-Spektren) sowohl mit dem Hauptrotamer (1b) als auch dem unterpopulierten Rotamer (1c) der Racemform jeweils gesicherter Konfiguration zugeordnet werden. Die Rotationsbarriere ΔG 301 ≠ von1a wurde durch CD- und Racemisierungs-Kinetik als 94.3 kJ mol−1 ermittelt.
    Notes: Summary Chiral crystals of “meso”-1,1′-bi(9,10-dihydro-9,10-ethano-anthryl) (1a) were obtained optically active by crystallization from chloroform/hexane by the vapor diffusion method (orthorhombic space group P212121). The chiroptical properties of1a were recorded in dichloromethane at 0 and 10°C, resp. ([α]D=−90°). Its absolute chirality is assigned assigned as (−)(R) a from chiroptical comparison (CD) both with the main rotamer (1b) and the underpopulated one (1c) of theracemic form of known chirality. The rotational barrier of1a was established as ΔG 301 ≠ =94.3 kJ mol−1 by CD-kinetics as well as by kinetics of racemization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810031
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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
    Optisch aktives 1,3-Diferrocenyl-1,3-diphenyl-allen (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 91-104 
    Details
    ISSN: 1434-4475
    Keywords: Chromatographic Resolution on Acetylcellulose ; Circular Dichroism ; 1,3-Diferrocenylbutadienes ; 1,3-Diferrocenylpropanes ; 1,3-Diferrocenylpropenes ; 1,3-Diferrocenylpropenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The title compound 2 was prepared by thermal dehydration of 1,3-diferrocenyl-1,3-diphenyl-propenol (24) with 70% yield.24 was accessible from 1,3-diferrocenyl-propanedione-1,3 (25) in two steps with 10% overall yield: Treatment of25 with phenyllithium gave 1,3-diferrocenyl-3-phenyl-propenone (8) which after repeated reaction with phenyllithium afforded24. Partial optical resolution of2 was achieved by chromatography on triacetyl cellulose in ethanol, whereby both (+)- and (−)-2 were obtained with different enantiomeric purities as could be deduced from the CD-spectra with Δε-values of +0.18 and −1.64, resp., at 480 nm. Attempts to prepare 1,3-diferrocenyl-allene and 1,3-diferrocenyl-1-phenyl-allene failed. In this context several 1,3-diferrocenyl-propenols,-propenones,-propenes,-propanones,-propanes and-butadienes were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00906246
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  • 10
    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.
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    URL: http://dx.doi.org/10.1007/BF00901830
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