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  • 1
    Electronic Resource
    Electronic Resource
    Bicyclic and Tricyclic Compounds with β-Amino Alcohol Groups as Chiral Ligands in the Enantioselective Reaction of Diethylzinc with Aldehydes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 423-434 
    Details
    ISSN: 0947-3440
    Keywords: 3,7-Dioxa-2-azabicyclo[3.3.0]octanes ; 2,6-Dioxa-3-azatricyclo[5.3.1.04.11]undecanes ; Amino alcohols ; Chiral ligands ; Enantioselective catalysis ; Homogenous catalysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of the enantiomerically pure allyloxy esters 9 or ent-9 with DIBAH afforded the corresponding aldehydes which were treated in situ with chiral or achiral hydroxylamines 8 to give nitrones 10. These underwent a spontaneous intramolecular 1,3-dipolar cycloaddition, affording the bicyclic compounds 11 and 12, respectively. In an analogous manner, a mixture of the tricyclic compounds 14 and 15 was prepared. Treatment of compound 16 with cyclohexene oxide afforded a mixture of diastereomers 17 and 18. Diastereomers 14 and 15 as well as 17 and 18 could be separated by chromatography. X-ray analyses of compounds 11Ff, 17, and 11Af · HCl were performed. The bicyclic and tricyclic compounds were used as chiral ligands in the reaction of diethylzinc with aldehydes 19, in particular with benzaldehyde (19a). Using bicyclic compounds with a tertiary β-hydroxyalkyl substitutent at the N atom as ligands, ee's in the range of 78 to 95% were found. Whereas for the best ligands 11Ae and Af the enantioselectivity in the reaction of 4-tolualdehyde was only slightly decreased, with the aliphatic aldehydes 19c and d distinctly lower enantioselectivities were determined.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970222
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  • 2
    Electronic Resource
    Electronic Resource
    ESR-Spektroskopische Untersuchungen an Donator-Acceptor-substituierten KohlenstoffradikalenHerrn Prof. Dr. K. Dimroth zum 70. Geburtstag gewidmet. (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 719-733 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: ESR Spectroscopic Studies of Donor-Acceptor-Substituted Carbon RadicalsThe radicals 2, 3a, 4, and 12 as well as 3b, and 17 were generated for ESR spectroscopic studies either by hydrogen abstraction with aminyl radicals or by oxidation with lead dioxide. Hydrogen abstraction from 5 did not give 6 but a secondary radical 7. Radical 16 was formed by reduction of the corresponding pyridinium iodide by zinc, whereas reduction of 13, and 8 afforded the radicals 15, and 11, respectively. The analysis of the ESR spectra allowed the determination of the spin density at various positions of these radicals. Furthermore, theoretical calculations of spin density - performed also for the radicals 1a and b, 21 and 22 - revealed the spin density distribution within the amino(cyano)alkyl group and the effects of further substituents on this.
    Notes: Die Radikale 2, 3a, 4 und 12 sowie 3b und 17 wurden durch H-Abstraktion mit Aminyl-Radikalen oder durch Oxidation mit Bleidioxid erzeugt und ESR-spektroskopisch untersucht. Bei H-Abstraktion aus 5 entstand nicht 6 sondern das Folgeradikal 7; Radikal 16 wurde durch Reduktion des entsprechenden Pyridiniumiodids mit Zink erhalten, während sich bei Reduktion von 13 oder 8 die Radikale 15 bzw. 11 bildeten. Die Analyse der ESR-Spektren ermöglichte die Bestimmung der Spindichte für eine Reihe von Positionen dieser Radikale. Außerdem durchgeführte theoretische Spindichteberechnungen - auch für die Radikale 1a und b, 21 und 22 - geben Aufschluß über die Spindichteverteilung in der Amino(cyan)alkylgruppe und deren Beeinflussung durch weitere Substituenten.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119810418
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  • 3
    Electronic Resource
    Electronic Resource
    Einfluß der Solvatisierung bei Umsetzungen von Nitrosobenzol mit Kalium-tert-butylat und anderen Basen (1981)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 1271-1284 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Effect of Solvation on the Reaction of Nitrosobenzene with Potassium tert-Butoxide and Other BasesThe reaction of nitrosobenzene (1) with potassium tert-butoxide (2) proceeds in benzene in the presence of crown ether or in tert-butyl alcohol via the dissociated ion 13a whereas in benzene alone the associated species 12 is formed.  -  Using tert-butyl alcohol as solvent, azoxybenzene (3), N-(4-nitrosophenyl)-N-phenylhydroxylamine (4), and N-phenylhydroxamic acid (5) are obtained; the nitrosobenzene anion radical 7 and methylphenylaminyl oxide (8a) were identified by ESR spectroscopy. The formation of 7 and 8a and their subsequent reactions are discussed.  -  Reactions in benzene yield mainly N-phenyl(2-nitrophenyl)amine (6) together with 4, but no 3 is formed. Instead of the radical 7 which cannot be detected in benzene (even not if 1 is treated with potassium-sodium alloy) another radical is generated for which the structure 11 is suggested.
    Notes: Die Reaktion zwischen Nitrosobenzol (1) und Kalium-tert-butylat (2) verläuft in Benzol bei Gegenwart von Kronenether sowie in tert-Butylalkohol über das dissoziierte lon 13a, in Benzol allein dagegen über die assoziierte Spezies 12.  -  In tert-Butylalkohol entstehen Azoxybenzol (3), N-(4-Nitrosophenyl)-N-phenylhydroxylamin (4) und N-Phenylformhydroxamsäure (5); das Nitrosobenzol-Anionradikal 7 und Methylphenylaminyloxid (8a) können ESR-spektroskopisch nachgewiesen werden. Die Bildung und Folgereaktionen von 7 und 8a werden diskutiert.  -  In Benzol wird N-Phenyl-(2-nitrophenyl)amin (6) als Hauptprodukt gebildet; daneben entsteht noch 4 aber nicht 3. Das Radikal 7 kann in Benzol (auch bei Reduktion von 1 mit Kalium-Natrium-Legierung) nicht beobachtet werden; stattdessen tritt ein Radikal auf, dem die Struktur 11 zugeschrieben wird.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198119810714
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  • 4
    Electronic Resource
    Electronic Resource
    Aminyloxide (Nitroxide), XXIII. Verhalten von N-tert-Butyl(3-oxoindolin-2-yliden)amin-N-oxid und N-tert-Butyl(3-oxo-3H-indol-2-yl)aminyl-N-oxid gegenüber Nucleophilen (1976)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1976 (1976), S. 432-439 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aminyl Oxides (Nitroxides), XXIII. - Reaction of N-tert-Butyl(3-oxoindolin-2-yliden)amine N-Oxide and N-tert-Butyl(3-oxo-3H-indol-2-yl)aminyl N-Oxide with NucleophilesIn the cyclic amidine N-oxide 1 as well as in its oxidation product 2 the carbonyl group is attacked by nucleophiles. From 1 formamidine N2-oxides 3 are formed by ring-opening, whereas different products result from reaction of 2. Ammonia, secondary amines or hydrogen cyanide yield only addition products 8. With hydroxide ions ring-expansion occurs with formation of 9a, which is easily transformed to carbamoylaminyl oxides 10a-e by further treatment with nucleophiles. The reaction of 2 and primary amines leads directly to 10f,g,the possible intermediates of type 9 not being detectable in this case.
    Notes: Sowohl im cyclischen Amidin-N-oxid 1 als auch in seinem Oxidationsprodukt, dem Radikal 2, wird die Carbonylgruppe von Nucleophilen angegriffen. Während aus 1 durch Ringöffnung die Formamidin-N2-oxide 3 entstehen, werden aus 2 verschiedene Produkte gebildet. So erhält man mit Ammoniak, sekundären Aminen oder Blausäure die Additionsprodukte 8. Mit Hydroxidionen erfolgt Ringerweiterung unter Bildung von 9a, das durch weitere Einwirkung von Nucleophilen in die Carbamoylaminyloxide 10a-e übergeht. Reaktion von 2 mit primären Aminen führt direkt zu 10f, g, ohne daß die wahrscheinlichen Zwischenstufen vom Typ 9 in diesem Falle nachgewiesen werden konnten.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197619760308
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemische Umlagerung eines 5-Imino-Δ3-isoxazolins (1970)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 732 (1970), S. 195-198 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photochemical Rearrangement of a 5-Imino-Δ3-isoxazoline5-Imino-2.3.4-triphenyl-Δ3-isoxazoline (1) is photochemically rearranged to 1.4.5-triphenyl-2-imidazolone (2) and 3-[(α-phenylamino)-benzylidene]-2-indolinone (3). The aziridinone 6 is believed to be the intermediate in the formation of 2.
    Notes: 5-Imino-2.3.4-triphenyl-Δ3-isoxazolin (1) läßt sich photochemisch in 1.4.5-Triphenyl-imidazolon-(2) (2) und 3-[(α-Phenyl-amino)-benzyliden]-indolinon-(2) (3) umlagern. Es wird angenommen, daß die Bildung von 2 über die Aziridinon-Zwischenstufe 6 erfolgt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19707320117
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  • 6
    Electronic Resource
    Electronic Resource
    Nitroxide, VII. Lösungsmittelabhängigkeit der ESR-Spektren von Alkyl-acyl-nitroxiden (1971)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 745 (1971), S. 159-163 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nitroxides, VII. Solvent Dependence in the ESR Spectra of Alkyl-acyl-nitroxidesThe nitrogen coupling constants aN of acyl-nitroxides 1 and 2 in aprotic solvents may be correlated with the ET-values for solvent polarity. The coupling constants aN in protic solvents are unexpectedly small. This is attributed to hydrogen-bonding at the carbonyl-oxygen which influences the distribution of spin density.
    Notes: Die Stickstoff-Kopplungskonstanten aN der Acyl-nitroxide 1 und 2 in aprotischen Lösungsmitteln lassen sich mit den ET-Werten für die Lösungsmittelpolarität korrelieren. Die unerwartet kleinen Kopplungskonstanten aN in protischen Lösungsmitteln werden auf Beeinflussung der Spindichte-Verteilung durch Wasserstoffbrücken-Bindung zum Carbonyl-Sauerstoff zurückgeführt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19717450119
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  • 7
    Electronic Resource
    Electronic Resource
    Nitroxide, X1) Darstellung und ESR-spektroskopische Untersuchungen von Phenyl-vinyl-nitroxiden (1972)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 762 (1972), S. 154-159 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nitroxides, X.-Synthesis of Phenylvinylnitroxides and their Investigation by ESR SpectroscopyIn the reaction of the nitriles 1 with aromatic nitroso compounds and potassium tert.-butoxide phenylvinylnitroxides 3 are formed. On the other hand, reaction of the α,β-dinitriles 4 with nitroso compounds yields 5-imino-Δ3-isoxazolines 5 which are converted into phenylvinylnitroxides 6 by oxidation. All radicals were investigated by ESR spectroscopy.
    Notes: Bei der Reaktion der Nitrile 1 mit aromatischen Nitrosoverbindungen in Gegenwart von Kalium-tert.-butylat entstehen die Phenyl-vinyl-nitroxide 3. Die α.β-Dinitrile 4 reagieren dagegen mit Nitrosoverbindungen zu den 5-Imino-Δ3-isoxazolinen 5, aus denen man durch Oxidation die Phenyl-vinyl-nitroxide 6 erhält. Alle Radikale wurden ESR-spektroskopisch untersucht.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19727620116
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  • 8
    Electronic Resource
    Electronic Resource
    An Intramolecular 1,3-Dipolar Cycloaddition Involving One Alkyne and Two Nitrone Groups (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 469-471 
    Details
    ISSN: 0947-3440
    Keywords: Cycloadditions ; Asymmetric Synthesis ; Heterocycles ; Alkynes ; Reductions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chiral nonracemic compound 4 was prepared from ethyl (S)-(-)-lactate and 1,4-dibromo-2-butyne. Reduction with DIBAH at -72°C and subsequent treatment of the resulting dialdehyde with N-methylhydroxylamine yielded the dinitrone 5, which underwent two consecutive intramolecular cycloadditions to give the chiral nonracemic compound 7. The structure of 7 was confirmed by an X-ray analysis. Reductive ring opening afforded compound 8.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970306
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  • 9
    Electronic Resource
    Electronic Resource
    Formation of tricyclic compounds in domino reactions of alkenal oximes (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1649-1653 
    Details
    ISSN: 0947-3440
    Keywords: 9-Oxa-3-thia-10-azatricyclo[6.2.1.04,10]undecanes, 6-heteroatom-substituted ; 3-Thiazoline N-oxides ; Mercaptoacetaldehyde ; 1,3-Dipolar cycloadditions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5-Alkenal oximes 4, 12, and 13 were prepared by various methods. These oximes undergo a domino reaction with mercaptoacetaldehyde (1-M) affording tricyclic compounds 6, 17 and 18, respectively. At first the mercapto group adds to the oxime function forming a hydroxyamino moiety which then condenses with the aldehyde group giving the cyclic nitrones 10, 15, and 16, resp., as intermediates. These nitrones undergo spontaneously an intramolecular cycloaddition yielding the tricyclic compounds (6, 17, 18). The regioselectivity of the latter reaction step is opposite to that observed for corresponding intermolecular nitrone cycloadditions. The domino reaction proceeds highly selectively affording only one of the diastereomers. Starting from enantiomerically pure oxime 13, we prepared optically active 18. The stereogenic center of 13 induces the formation of three further stereogenic centers in the product. The configuration at C-5 of 18 was determined by a NOESY experiment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199509229
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  • 10
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der Reaktion von Methylenaminen mit aromatischen Nitrosoverbindungen (1975)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1975 (1975), S. 1307-1316 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Mechanistic Studies of the Reaction of Methyleneamines and Aromatic Nitroso CompoundsThe course of the reaction of methyleneamines 1 and nitroso compounds 2 to amidine N-oxides 3 was studied by 1H-NMR- and electron spectroscopy. The retardation of the reaction by diarylaminyl radicals proves it to proceed via radical intermediates. The reaction is catalysed by 3, as well as by reducing agens like tert.-butylhydroxylamine and hydroquinone. The results indicate a mechanism with the radicals 8 and/or 9, respectively, as intermediates.
    Notes: Der Verlauf der Reaktion zwischen Methylenaminen 1 und Nitrosoverbindungen 2 zu den Amidin-N-oxiden 3 wurde 1H-NMR- und elektronenspektroskopisch verfolgt. Die Hemmung der Reaktion durch Diarylaminylradikale zeigt einen radikalischen Verlauf an. Die Umsetzung wird durch 3 selbst katalysiert, ebenso durch Reduktionsmittel wie tert.-Butylhydroxylamin und Hydrochinon. Aufgrund der Ergebnisse wird ein Mechanismus über die Radikale 8 und/oder 9 formuliert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197519750709
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