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  • Chemistry  (18)
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  • 1
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Arylsubstituted Δ2-1,3,4-Oxadiazolines. II. The Influence of the Substituents and the Solvent on the Absorption and Fluorescence Properties of Arylsubstituted Δ2-1,3,4-OxadiazolinesThe electronic absorption and the fluorescence spectra of 16 arylsubstituted Δ2-1,3,4-oxadiazolines were measured in benzene at room temperature.The push-pull effect of the substituents supports an increasing intramolecular charge-transfer in the electronically excited singlet state, which increases its dipole moment relative to the ground state.The significant linear correlation of the Hammett σp-values with the energies of the fluorescence and absorption maxima of the Δ2-oxadiazolines, p-substituted in the phenylring at the C 2-atom, demonstrate these intramolecular charge transfer.The titel compounds demonstrate with increasing solvent polarity a bathochromic shift of the absorption maxima.For some oxadiazolines the dipole moment for the excited singlet state proved to be about 30 Cm as Stoke's shift dipendency from the solvent indicate.
    Additional Material: 5 Ill.
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  • 2
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azomethineimine. VI. On the Thermic Behaviour of the Photochromic System Azomethineimine/Diaziridine, Investigated by Means of the Photoproducts of Pyrazolidone-(3)-AzomethineiminesThe photochemically obtained cycloproducts 2 of pyrazolidone-(3)-azomethineimines 1 react thermically to 1 in aprotic solvents. This backreaction was investigated by following up the growth of the intensive long wave absorptionband of 1. The kinetic analysis was carried out according to SWINBOURNE [5, 6]. The thermic backreaction is accelerated by factors favouring a polarization of the C—N(2)-bond (Cδ+ — Nδ-) of diaziridine 2. Such factors are polar solvents, donors in the substituent R and extensive, easily polarizable π-electronic systems in R. The influence of substituents on the backreaction can be correlated by means of the σ+-Hammett-constants. For most compounds the values of EA ≈ ΔH≠, Δ≠ and ΔG≠ were determined. The possible reaction mechanism is discussed. The influence of steric factors on the thermic backreaction is regarded as a first indication of an exo-form of the bicyclic diaziridines 2.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 205-210 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azomethineimines. VII. Photochemical and Thermic Behaviour of Azarylsubstituted Pyrazolidone-(3)-AzomethineiminesIn principle the photochemical behaviour of azarylsubstituted pyrazolidone-(3)-azomethineimines 1 does not differ from other pyrazolidone-(3)-azomethineimines. Except for the acridyl-(9)-substituted compound in aprotic solvents they react to bicyclic diaziridines 2. The quantum yield of this reaction has a value of nearly 0.3. For two of the diaziridines 2 the photochemical backreaction was realized. Results of the investigation of the thermic backreaction show the expected stability of the bicyclic diaziridines 2a-d. All the investigated compounds have a pronounced tendency towards several irreversible side reactions.
    Additional Material: 2 Tab.
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  • 4
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions by Participating of Ylide-Intermediates. III. On Preparation and Structural Elucidation of Spiro-condensed TetrahydroindolizinesN-(Fluroen-9-yl)-pyridinium- and -isoquinolinium ylides (5) to (8) react with electrondeficit olefinic dipolarophiles under mild conditiones to give satisfactory to good yields of the corresponding spirocondensated tetrahydroindolizines (10) to (13). The structure and configuration of all isolated products were elucidated by spectroscopical methods, especially by 1 D- and 2 D 1H-n.m.r. The 1.3-dipolar cycloaddition produced regiospecific cycloadducts. From the observed regiospecifity of unsymmetrically substituted olefines (9) can be concluded that the cycloaddition is HOMO(1.3-dipole)  -  LUMO(dipolarophile) controlled. The olefines (9) add stereospecifically under retention of their configuration via exo as well as endo transition states. The nitrosubstituted ylides (6) and (8) produced always mixtures of diastereomeric cycloadducts (11) and (13).
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 903-909 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Azomethineimines. V. 1H-N.M.R. Spectra and Steric Properties of Arylsubstituted Pyrazolidone-AzomethineiminesFrom the results of 1H-n.m.r.-spectroscopic investigations we tried to draw conclusions regarding the steric properties of pyrazolidone-azomethineimines 1a-k. The influence of aromatic systems on chemical shift of the methineproton of the 1,3-dipolar centre was calculated using the ring current model. Without the twisted 9-anthryl-substituted compound 1f experimental results show a good correspondence to the values of chemical shift calculated for two of four possible isomeric structures.
    Additional Material: 3 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 910-914 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of α-Cyano-β-aryl Acrylic Acid Ethylesters with Hydrazine, a Retro-Knoevenagel-ReactionWe tried to obtain 4-cyano 5-aryl pyrazolidones-(3) 3a, b and related azomethine imines 4a, b. However the reaction of α-cyano β-aryl acrylic acid ethylesters 2a, b with hydrazine yields the familiar cyano acetic acid arylidene hydrazides 5a, b by cleavage of the carbon-carbon double bond. 5a, b react with pyrene-1-aldehyde to 7a, b. Formation of 5a, b is proved by an independent synthesis. 5a, b and 7a, b are investigated by mass spectrometry.
    Additional Material: 3 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 322 (1980), S. 623-628 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azomethine-Imines. I. To the Photoreversibility of the System Azomethine-Imine/Diaziridine,Investigated on Pyrazolidone-Azomethine-IminesPyrazolidone-azomethine-Imines of the type 1 with polycyclic aromatic substituents R undergo a photoreversible reaction to diaziridines 2. In the u.v./VIS-spectra of the two forms 1 and 2 the difference of the λmax-values is about 100 nm. Therefore this system is suitable as a new reversible photochromic system. The influence of substituents R′ to the u.v./VIS-spectra of the 1.3-dipolar form 1 is discussed.
    Notes: Die seit langem bekannten Pyrazolidon-Azomethinimine 1 sind als carbonylstabilisierte 1,3-Dipole aufzufassen und lassen sich relativ leicht synthetisieren [1, 2]. Später wurde erkannt, daß diese Verbindungen beim Belichten aus der 1,3-Dipolform 1 in die bicyclische Diaziridinform 2 übergehen und daß diese Reaktion thermisch reversibel ist [3]. Uns interessierte die Frage, ob die Diaziridine 2 auch photochemisch wieder in die Dipolform überführbar sind.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 96-102 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Diarylsubstituted 2H-Tetrazoles. II. The Influence of the Substituents on the Absorption Properties of Diarylsubstituted NitriliminesIrradation of 2,5-diaryl-2H-tetrazoles in an EPA-glass (ether: i-pentan: ethanol=5:5:2) or in an i-pentan glass at 77-80 K with UV-light of wavelength 290 nm yields diarylnitrilimines by the extrusion of nitrogen. The photoreactions investigated show spectroscopic unity. 22 diarylnitrilimines are included in the discussion with regards to the influence of substituents on the absorption maxima. The influence of substituents is interpreted by a LFE-relationship. An intramolecular charge transfer as the reason for the relatively strong dependence of νa∼max-values on substituents is discussed.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 256-259 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es werden neue Methoden zur Herstellung von phosphororganischen Isocyanaten durch Umsetzung von phosphororganischen Amidsalzen mit Phosgen oder Oxalylchlorid und aus N-Diphenyl-phosphinsäureureiden mit Phosgen beschrieben. Phosphonsäurediureide liefern mit Phosgen Dioxo-triazaphosphorinane.
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  • 10
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemistry of Diarylsubstituted 2H-Tetrazoles, XI and Sydnones. V. Flashphotolytic Investigations with 2,5-Diaryl-2H-tetrazoles and 3,4-Diarylsydnones. Absolute Rate Constants of Cycloadditionreactions of Diarylnitrile Imines to DipolarophilsThe flash photolysis of 2,5-Diaryl-2H-tetrazoles 1 and 3,4-Diarylsydnones 2 was investigated. The nitrile imines were detected spectroscopically as short living intermediates. Rate constants of the cycloaddition reaction of nitrile imines and dipolarophiles were determined and the influence of substituents in the dipolarophile as well as in the nitrile imine is discussed. The results agree quite well with SUSTMANN'S theroetical classification of 1,3-dipolar cycloaddition reactions.
    Additional Material: 6 Ill.
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