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  • 1
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, II. Zur Regio- und Stereoselektivität der radikalischen Cyclopentan-Synthese aus Dienen über Alkenylquecksilbersalze (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 363-368 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Radical Type Cyclisation of Dienes, II. - The Regio-and Stereoselectivity of Radical Cyclopentane Synthesis from Dienes via Alkenylmercury SaltsWhen ethyl 8-methoxy-2,7-octadienoate (1) is treated with mercury(II) acetate in the presence of calcium oxide and methanol followed by reduction with NaBH4 a mixture of ethyl cis- and trans-[2-(dimethoxymethyl)cyclopentyl]acetate (cis-2 and trans-2) is obtained regioselectively in 90% yield. Under analogous conditions ethyl (1′S,2′S3′R,4′R)-[3-(dimethoxymethyl)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]acetate (4a) is obtained exclusively in a regio- and stereoselective manner from ethyl (1′S,3′S)-3-[3-(2-methoxyethenyl)-1,2,2-trimethylcyclopentyl]propenoate (3) in 70% yield. This proves radical type cyclisations of optically active derivatives of 1 to proceed not only regioselectively but also with high stereoselectivity.
    Notes: Bei der Umsetzung von 8-Methoxy-2,7-octadiensäure-ethylester (1) mit Quecksilber(II)-acetat in Gegenwart von Calciumoxid und Methanol und anschließender NaBH4-Reduktion wird regioselektiv in 90proz. Ausbeute ein Gemisch von cis- und trans-[2-(Dimethoxymethyl)cyclopentyl]essigsäure-ethylester (cis-2a und trans-2a) erhalten. Unter analogen Reaktionsbedingungen entsteht aus (1′S,3′S)-3-[3-(2-Methoxyethenyl)-1,2,2-trimethylcyclopentyl]propensäure-ethylester (3) regio- und stereoselektiv in 70 proz. Ausbeute nur (1′S,2′S,3′R,4′R)-[3-(Dimethoxymethyl)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]essigsäure-ethylester (4a). Damit ist sichergestellt, daß die radikalische Cyclisierung von optisch aktiven Derivaten von 1 unter den angegebenen Reaktionsbedingungen nicht nur regioselektiv, sondern auch mit hoher Stereoselektivität verläuft.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210224
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  • 2
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, III Radikalische Cyclisierung von (R)-(-)-Carvon - Über den Einfluß von Charge-Transfer-Wechselwirkung auf den spezifischen Drehwert (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 901-905 
    Details
    ISSN: 0009-2940
    Keywords: Radical-type cyclisation / Bicyclo[3.2.]octan-3-one, enantiomerically pure / Charge-transfer interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclisation of Dienes, 111. - Radical-Type Cyclisation of (R)-( - )-Carvone - On the Influence of Charge- Transfer Interactions on the Optical RotationUnder the conditions of radical cyclisation, a 1:1 diastereomeric mixture of (1R,2S,5R,R)-(+)- (2a) and (1R.2S,5R,6S)-(+)-6-methoxy-2,6-dimethylbicyclo[3.2.1]octan-3-ones (2b) is obtained from (R)-(-)-carvone in 70% yield. the configuration fo 2a and 2b were confirmed by X-ray structure analyses of their hydrazones 2d and 2e. The regio- and stereoselectivity of the radical cyclisation of 1 to 2a and 2b are discussed. The high value of the specific rotation [-555] of 2d is traced back to charge-transfer interactions between the endo-standing methoxy group at C-6 as electron donor and the dinitrophenyl-hydrazone group as electron acceptor.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230441
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  • 3
    Electronic Resource
    Electronic Resource
    Kondensierte Ringsysteme, XVII. Propellane mit Benzol-Dewarbenzol-Struktur - Kristall- und Molekülstruktur von 1′,8′:3,5-Naphtho[5.2.2]propella-3,8,10-trien (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 1540-1545 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Condensed Ring Systems, XVII. Propellanes with Benzene-Dewar-Benzene Structure  -  Crystal and Molecular Structure of 1′,8′:3,5-Naphtho[5.2.2]propella-3,8,10-trieneThe syntheses of the propellanes 7-9, which have a benzene-Dewar-benzene structure, are described. As a second example of a 1,4-bridged Dewar-benzene, the crystal and molecular structure of 1′,8′:3,5-naphtho[5.2.2]propella-3,8,10-triene (9) is elucidated by X-ray structure analysis. 9 has a long central bridge bond of 1.565 Å, which, however, is clearly shorter than the corresponding bond of 3,4:5,6-dibenzo[6.2.2]propella-3,5,9,11-tetraene (10: 1.586 Å), due to the smaller C5-bridge. The dihedral angle of 116.6° between the cyclobutene rings of the Dewarbenzene system of 9 is insignificantly larger than the analogous angle of 10 (115.9°). The molecule lies on a crystallographic mirror plane.
    Notes: Die Synthesen der Propellane 7-9, die eine Benzol-Dewarbenzol-Struktur besitzen, werden beschrieben. Als zweites Beispiel für ein 1,4-überbrücktes Dewarbenzol wird die Kristall- und Molekülstruktur von 1′,8′:3,5-Naphtho[5.2.2]propella-3,8,10-trien (9) mittels Röntgenbeugung bestimmt. 9 besitzt eine lange zentrale Brückenbindung mit 1.565 Å, die jedoch aufgrund der kleineren C5-Brücke deutlich kürzer als die entsprechende Bindung im 3,4:5,6-Dibenzo[6.2.2]-propella-3,5,9,11-tetraen (10: 1.586 Å) ist. Der Faltungswinkel zwischen den beiden Cyclobutenringen des Dewarbenzol-Systems beträgt 116.6° und ist damit nur unwesentlich größer als der von 10 (115.9°). Das Molekül liegt auf einer kristallographischen Spiegelebene.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861190509
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  • 4
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, VIII. Über die regioselektive Herstellung von ungesättigten Cyclopenta[b]furan-2-onen aus (S)-(+)-Carvon  -  Bausteine zur Synthese von enantiomerenreinen Triquinanen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 549-550 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Cyclization ; Triquinanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dienes, VIII[1].  -  On the Regioselective Synthesis of Unsaturated Cyclopenta[b]furan-2-ones from (S)-(+)-Carvone  -  Building Blocks for the Synthesis of Enantiomerically Pure TriquinanesThe diastereomeric products 2a and 2b, which were synthesized from (S)-(+)-carvone (1), are converted to (3aS,5S,6aS)-(-)-5-acetoxyhexahydro-6a-methyl-2H-cyclopenta[b]furan-2-one (4) in ca. 50% yield. 4 is regioselectively converted to (3aR,6aS)-(-)-3,3a,6,6a-tetrahydro-6a-methyl- (8a) and (3aS,6aR)-(+)-3,3a,4,6a-tetrahydro-6a-methyl-2H-cyclopenta[b]-furan-2-one (8b). These are used at the 10-g scale for the synthesis of enantiomerically pure triquinanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270314
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  • 5
    Electronic Resource
    Electronic Resource
    Radikalische Cyclisierung von Dienen, IX. Über die Stereoselektivität der radikalischen 4-exo-trig-Cyclisierung von optisch aktiven (2E)-6-Oxohex-2-ensäureestern mit Samarium(II)-iodid (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1305-1309 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Cyclobutanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dienes, IX. - On the Stereoselectivity of the Radical 4-exo-trig-Cyclization of Optically Active Ethyl (2E)-6-Oxohex-2-enoates with Samarium(II) IodideEthyl (5R, 2E)-5-(benzyloxy)-4,4-dimethyl-6-oxohex-2-enoate (9) was prepared from (R)-(-)-pantolactone (3) by a series of straightforward reactions. The reaction of 9 with samarium(II) iodide produces enantiomerically pure ethyl (1S,3R,4R)-(-)-[3-(benzyloxy)-4-hydroxy-2,2-dimethylcyclo-butyl]acetate (10) in 60% yield. The absolute configuration at C-1 and C-3 was confirmed by the conversion of 10 to the crystalline 15a, whose absolute configuration is known from its synthesis from (1S,5S)-( + )-α-pinene (12). The configuration of the hydroxy group at C-4 in 10 was determined from NOE studies on the epimiric 17. The radical 4-exo-trig-cyclization of optically active (2E)-6-oxohex-2-enoates with samarium(II) iodide opens a new pathway to enantiomerically pure cyclobutanol and cyclobutanone derivatives, which are of interest as building blocks in natural products synthesis.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270720
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  • 6
    Electronic Resource
    Electronic Resource
    Kondensierte Ringsysteme, XVIII Zur Synthese von Cyclobuten-Derivaten aus den entsprechenden Thiolanen - Kristall- und Molekülstruktur von 2,5-o-Benzeno-3,4-benzo[4.2.2]propella-3,7,9-trien (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 5-9 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclobutene derivatives are prepared from the corresponding thiolanes in better yields by using the chloro sulfoxides than the chloro sulfones, which are intermediates in the Ramberg-Bäcklund reaction. This is established by the synthesis of 2,5-o-benzeno-3,4-benzobicyclo[4.2.0]octa-3,7-diene (6) from 2,5-o-benzeno-3,4-benzo-8-thiabicyclo[4.3.0]non-3-ene (1). On the same way 2,5-o-benzeno-3,4-benzo[4.2.2]propella-3,7,9-triene (8) can now be prepared in better yields and its X-ray structure analysis is described.
    Notes: Cyclobuten-Derivate lassen sich aus den entsprechenden Thiolanen über die Chlorsulfoxide in besseren Ausbeuten herstellen als über Chlorsulfone, die bei der Ramberg-Bäcklund-Reaktion als Zwischenprodukte auftreten. Dieses wird durch die Synthese von 2,5-o-Benzeno-3,4-benzobicyclo[4.2.0]octa-3,7-dien (6) aus 2,5-o-Benzeno-3,4-benzo-8-thiabicyclo[4.3.0]non-3-en (1) bewiesen. Auf dem gleichen Syntheseweg konnte jetzt auch das 2,5-o-Benzeno-3,4-benzo[4.2.2]propella-3,7,9-trien (8) in besserer Ausbeute erhalten werden, dessen Röntgenstrukturanalyse beschrieben wird.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200103
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation of Kingiside from Aucubin (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1623-1626 
    Details
    ISSN: 1434-193X
    Keywords: Iridoid glucoside ; (8S)-Kingiside ; (8S)-Loganin ; (8S)-7-Ketologanin ; Asymmetric synthesis ; Natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Nichtproteinogene Aminosäuren, III Synthese der enantiomerenreinen 2-(2-Thienyl)- und 2-(3-Thienyl)-glycine - Molekülstruktur der als Zwischenprodukte auftretenden Schiffschen Basen (1985)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1985 (1985), S. 566-578 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nonproteinogenic Amino Acids, III. - Syntheses of the Enantiomerically Pure 2-(2-Thienyl)-and 2-(3-Thienyl)glycines. - Molecular Structure of the Intermediate Schiff's BasesThe syntheses of enantiomerically pure D-(-)- and L-(+)-2-(2-thienyl)- and 2-(3-thienyl)glycines (6a - d) are described. Preparing the amino nitriles 4 directly from 2-thiophenecarbaldehyde (1a) or 3-thiophenecarbaldehyde (1b), respectively, and (4S, 5S)-(+)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane (2), and hydrocyanic acid (one-step procedure), the aminonitriles 4a and 4b, respectively, are formed in excess. By crystallization they are obtained diastereomerically pure leading to enantiomerically pure D-amino acids 6a and 6b. If, however, the intermediate Schiff's bases 3 are isolated as crystals and then converted with hydrocyanic acid into the respective aminonitriles 4 (two-step procedure), the diastereomeric aminonitriles 4c and 4d, respectively, crystallize resulting in enantiomerically pure L-amino acids 6a and 6d. X-ray structure analyses of the Schiff's bases 3c and 3e revealed the previously postulated E-configuration of the C = N bond and its chiral shielding by the phenyl substituent at C4.
    Notes: Es wird die Synthese von enantiomerenreinem D-(-)-und L-(+)-2-(2-Thienyl)- und 2-(3-Thienyl)-glycin (6a - d) beschrieben. Werden die Aminonitrile 4 direkt aus 2-Thiophencarbaldehyd (1a) oder 3-Thiophencarbaldehyd (1b), (4S,5S)-(+)-5-Amino-2,2-dimethyl-4-phenyl-1,3-dioxan (2) und Blausäure hergestellt (Einstufen-Verfahren), so entstehen im Überschuß die Aminonitrile 4a und 4b, die durch Kristallisation diastereomerenrein erhalten werden und zu den enantiomerenreinen D-Aminosäuren 6a und 6b führen. Werden dagegen die Schiffschen Basen 3 kristallin isoliert und mit Blausäure zu den entsprechenden Aminonitrilen 4 umgesetzt (Zweistufen-Verfahren), so kristallisieren die diastereomeren Aminonitrile 4c und 4d aus, die zu den enantiomerenreinen L-Aminosäuren 6c und 6d führen. Die Röntgenstrukturanalysen der Schiffschen Basen 3c und 3e bestätigen die früher angenommene E-Konfiguration der C = N-Bindung und deren chirale Abschirmung durch den Phenylsubstituenten an C4.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198519850318
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  • 9
    Electronic Resource
    Electronic Resource
    Chemie und Stereochemie der Iridoide, VIII. Über die Oxidation der Enolether-Funktion von Catalpol-Derivaten zum Lacton (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 227-230 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry and Stereochemistry of Iridoids, VIII. - Oxidation of the Enol-Ether Function of Catalpol Derivatives to the LactoneOxidation of 2′,3′,4′,6,6′,10-hexaacetylcatalpol (1a), 2′,3′,4′,6-tetraacetyl-6′,10-bis(triphenylmethyl)catalpol (1b), and 2′,3′,4′,6′,10-pentaacetyl-6-(acetylvanilloyl)catalpol (1c) by N-bromosuccinimide/dimethyl sulfoxide is described. A mixture of the two possible diastereomeric α-bromolactones 2 is obtained in each case. This mixture can be reduced as crude product in dry tetrahydrofuran by treatment with zinc/acetic acid to yield more than 70% of the halogen-free lactones 3. The mechanism of the reaction is discussed.
    Notes: Die Oxidation von 2′,3′,4′,6,6′,10-Hexaacetylcatalpol (1a), 2′,3′,4′,6-Tetraacetyl-6′,10-bis(triphenylmethyl)catalpol (1b) und 2′,3′,4′,6′,10-Pentaacetyl-6-(acetylvanilloyl)catalpol (1c) mit N-Bromsuccinimid/Dimethylsulfoxid wird beschrieben. Das jeweils entstehende Diastereomerengemisch der zwei möglichen α-Bromlactone 2 läßt sich als Rohprodukt mit Zink/Eisessig in wasserfreiem Tetrahydrofuran zu den halogenfreien Lactonen 3 reduzieren, wobei die Gesamtausbeuten höher als 70% sind. Der Reaktionsmechanismus wird diskutiert.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870312
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  • 10
    Electronic Resource
    Electronic Resource
    Chemistry and Stereochemistry of Iridoids, X. Enantiomerically Pure Hexahydropentalene Derivatives - Building Units for the Synthesis of Cyclopentanoid Natural Products (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 679-682 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemie und Stereochemie der Iridoide, X. - Enantiomerenreine Hexahydropentalen-Derivate. - Bausteine zur Synthese von cyclopentanoiden NaturstoffenEs wird die Synthese der enantiomerenreinen Hexahydropentalen-Derivate 5a-5e aus dem Iridoidglucosid Catalpol beschrieben. Mit dem kristallinen Camphansäureester 5e wird die in der Literatur angegebene absolute Konfiguration des durch Racematspaltung hergestellten (1α,3aβ,6aβ)-1,2,3,3a,4,6a-Hexahydro-1-pentalenols (5d) bestätigt.
    Notes: The synthesis of the enantiomerically pure hexahydropentalene derivatives 5a-5e starting from the iridoid glucoside catalpol is described. The absolute configuration reported for (1α,3aβ,6aβ)-1,2,3,3a,4,6a-hexahydro-1-pentalenol (5d), which has been obtained by optical resolution, is confirmed by preparation of the crystalline camphanate 5e.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870807
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