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  • 1
    Monograph available for loan
    Monograph available for loan
    Part 2: methods/workshop papers (2001)
    Marburg : Metropolis
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    Call number: PIK B 160-01-0663
    In: Sustainability in the information society
    Type of Medium: Monograph available for loan
    Pages: 498-1036 S.
    Series Statement: Sustainability in the information society
    Location: A 18 - must be ordered
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  • 2
    Monograph available for loan
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    Part 1: Impacts and applications (2001)
    Marburg : Metropolis
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    Call number: PIK B 160-01-0662
    In: Sustainability in the information society
    Type of Medium: Monograph available for loan
    Pages: 1-492 S.
    Series Statement: Sustainability in the information society
    Location: A 18 - must be ordered
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  • 3
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der photochemischen Umwandlung von 2-Alkyl-indazolen in 1-Alkyl-benzimidazole. II. Photophysikalische und photochemische Primärprozesse (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1528-1546 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic studies on the photoisomerization of 2-alkyl-indazoles into 1-alkyl-benzimidazoles. II. Primary photochemical processes and photophysical deactivation.In the previous paper [1] the structure of the intermediate in the photochemical indazole-benzimidazole-isomerization was discussed (3 in Scheme 1). In this communication experiments concerning the photochemical primary processes and photophysical deactivation of 2-alkyl-indazoles (1) are described.The quantum yield of the rearrangement 1 → 2 (ΦR) decreases with decreasing temperature while the fluorescence quantum yield (ΦF) increases and finally reaches a constant value ( ≠ 1) (Fig.10). This behaviour is inconsistent with the mechanism shown in Scheme 2. Photoreaction and fluorescence are both quenched, but not to the same extent, by freon 113 (Fig. 2). In addition the Stern-Volmer-plots are not linear. These observations are best explained by assuming the existence of two excited states in equilibrium (Scheme 3). The mechanism in Scheme 3 correctly explains the quenching experiments and the temperature dependence of ΦR and ΦF if the Arrhenius law holds for the two rate constants ksx and kR. However, for a quantitative calculation of ΦR, an additional branching of the reaction pathway must be postulated (Scheme 4). Two-dimensional drawings of hypothetical potential energy surfaces of the ground state and the first excited singlet state yielding a qualitative picture of the reaction and deactivation pathways of the discussed molecule are given in Fig. 15 a and b.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590513
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  • 4
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der photochemischen Umwandlung von 2-Alkyl-indazolen in 1-Alkyl-benzimidazole. I. Struktur und Reaktivität eines Zwischenproduktes (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 1512-1527 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic studies on the photoisomerization of 2-alkyl-indazoles into 1-alkyl-benzimidazoles. I. Structure and reactivity of an intermediate.2-Alkyl-indazoles (1) undergo photochemical isomerization to 1-alkyl-benzimidazole via previously unknown intermediates 3 (Scheme 1). In the present paper the structure and reactivity of these intermediates are discussed. Low-temperature irradiation (-60°) of 1 b with 300 nm light gives 3 b in quantitative yield. 3 b is transformed during warm-up to 1 b and 2 b (UV.-evidence). The formations of 1 and 2 show the same temperature dependence but their ratio is found to be temperature-independent. In contrast to the above behaviour, low-temperature irradiation with 250 nm light of 3 b yields 1 b only (no 2 b). These findings are consistent with the proposed reaction mechanism 2 c in Scheme 2.On the basis of spectroscopic properties and the described reaction pathways, it appears that the most suitable structure for intermediate 3 is a 7,8-diaza-tricyclo[4.3.0.07,9]nona-2,4,6(10)-trien (9). In Scheme 4 the reaction pathway for the iudazole-benzimidazole-rearrangement is summarized.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590512
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  • 5
    Electronic Resource
    Electronic Resource
    Zum Mechanismus der Photochemie von 2-Alkylindazolen in wässerigen Lösungen (1976)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 2362-2373 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanistic studies on the photochemistry of 2-alkylindazoles in aqueous solutions.The photochemistry of 2-alkylindazoles 1 in aqueous solutions is rather complex, the relative yields of different products being dependent on the pH-value of the irradiated solution: In neutral or basic solutions (pH 〉 7) as well as in most of the organic solvents isomerization to 1-alkyl-benzimidazoles 2 takes place. In dilute sulfuric acid (pH 2-4) this reaction is suppressed and the dihydro-azepinones 3 and 4 are formed. Irradiation in strongly acid solutions (pH 〈 1) yields the o-amino-acetophenones 5 (Scheme 1).The relative quantum yields of the photoproducts 2-5 have been measured as a function of the pH-value of the irradiated solution (Fig. 1). A comparison of these yields with the protonation equilibrium of the indazole in its first excited singlet state (pK = 2.8) suggests that 2 and 3 are both photoproducts of the neutral indazole molecule, whereas 4 as well as 5 are formed from the protonated indazole.The rearrangement of the indazole 1 to the benzimidazole 2 proceeds via an intermediate 6, which can be produced in high concentrations by monochromatic irradiation of 1 at low temperatures. The thermal reactivity of this intermediate in dilute sulfuric acid could be investigated: At pH 8 the only product is the benzimidazole 2. With decreasing pH-value increasing amounts of 3 are formed and at pH 〈 4 the formation of 2 is completely suppressed, the only product being the azepinone 3. Thus, 3 is a solvolysis product of the intermediate 6 (Scheme 2).The most probable primary product of singlet indazolium is the nitrenium ion 7. From this intermediate the formation of 5 can proceed in well-known thermal reactions. The formation of 4 is possibly due to a further protonation equilibrium nitrenium-nitrene. The nitrene 7 can be converted into the azepinone 4 via the azirine 8 (Scheme 3). The pK-values of different indazoles and intermediates are listed in the Table.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19760590709
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  • 6
    Electronic Resource
    Electronic Resource
    Synthese von 2H-Isoindol-4,7 -dionen durch photochemische Cycloaddition von 2,3-Diphenyl-2H-azirin an 1,4-Chinone. 38. Mitteilung über Photoreaktionen37. Mitt. siehe [1]. (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2634-2643 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2, 3-Diphenyl-2H-azirine (1) reacts on irradiation with light of wavelength 290-350 nm with 1,4-benzoquinones 3-6 or with 1,4-naphthoquinones 7-9 forming the yellow to red coloured 1,3-diphenyl-2H-isoindole-4, 7-diones 10-13 (33-43% yield) resp. 1, 3-diphenyl-2H-benzo[f]isoindole-4,9-diones 14-16 (33-36% yield) (Scheme 1). The structures of these hitherto unknown products follow from the analytical and spectral data.The probable formation of the isoindole-diones is depicted in Scheme 2. The intermediate benzonitrile-benzylide (2), which most certainly arises, adds onto the unsubstituted C, C-double bond of the quinones and not onto the C,O-double bonds. On exclusion of atmospheric oxygen there results from 1 and 2-methyl-1, 4-benzoquinone (4) a product (probably b) which hardly absorbs in the region 350-450 nm. The latter, with the agency of atmospheric oxygen (but not 4), is converted into 5-methyl-1, 3-diphenyl-2H-isoindole-4, 7-dione (11). The relative slowness of this oxidation (see Fig. 2) enables an almost complete photochemical transformation of the azirine 1, which only weakly absorbs above 290 nm. Otherwise 11, which strongly absorbs above 290 nm, would hinder the photolysis of 1.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570842
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  • 7
    Electronic Resource
    Electronic Resource
    Tieftemperaturbestrahlungen von 3-Phenyl-2H-azirinen27. Mitt. über Photoreaktionen; 26. Mitt. [1]. 25. Mitt. [2]. (1973)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 56 (1973), S. 1679-1690 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2, 2, 3-Triphenyl-2H-azirine (4a) in a matrix of 2, 2-dimethylbutane/pentane 8:3 (DMBP) at -185° gave rise on irradiation with light of 250-350 nm to a new UV.-maximum at 350 nm (Fig. 1). We assign the dipole benzonitrildiphenylmethylide (1a) to this new maximum. Irradiation with monochromatic light of 366 nm destroyed this maximum and the initial absorption curve reappeared (Fig. 2). When the azirine 4a was photolysed in DMBP at -185° in the presence of methyl trifluoracetate (TFEM), the maximum at 350 nm was obtained again. This maximum vanished upon increasing the temperature to -160°. Through gas chromatography we were able to show that 5-methoxy-5-trifluormethyl-2, 2, 4-triphenyl-3-oxazoline (6a) was produced. 6a was also obtained upon irradiation of 4a at room temperature in the presence of TFEM (scheme 1 and table 1). Modification of the previously described experiment, in which the maximum at 350 nm was extinguished in the matrix due to irradiation at 366 nm gave, after warm up, almost no dipole adduct 6a (table 1). From these experiments, an extinction coefficient of 17, 000 for the 350 nm maximum of 1a, was calculated. These experiments have shown that irradiation of triphenylazirine 4a leads to the dipole 1a, which can be reversed photochemically - but not tharmally - into azirine 4a. 1a reacts at less than -160° with TFEM to give adduct 6a. The results which were obtained with triphenylazirine 4a could be correspondingly obtained with 2, 3-diphenyl-2H-azirine 4b (Fig. 3, scheme 2 and table 2). The dipole 1b showed two UV.-maxima at 330 nm (ε = 17, 500) and 343 nm (ε = 21, 000). Later experiments established, that the two maxima belonged to a single dipole species.The dipole 1c obtained upon irradiation of 2, 2-dimethyl-3-phenyl-2H-azirine (4c) in DMBP at -190°, appears to absorb in the same region as the azirine 4c. The presence of the dipole 1c was univocally established by low temperature trapping experiments with TFEM. The dipole 1a showed no ESR.-spectrum characteristic for a triplet state. We assume therefore, that 1a is in a singlet state. Photolysis of oxazolinone 7 at -190° in DMBP led to the dipole 1a with loss of CO2. 1a recombines apparently in considerable amount with the CO2 trapped in the matrix to give starting oxazolinone 7 because the 350 nm-maximum of 1a appeared with low extinction. Irradiation with light of 366 nm into this matrix produccd triphenylazirine 4a. Low temperature trapping experiments with TFEM led to small amounts of 5-methoxy-5-trifluormethyl-triphenyl-3-oxazolinc (6a).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19730560525
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  • 8
    Electronic Resource
    Electronic Resource
    Photoinduzierte 1, 3-dipolare Cycloaddition von 3-Phenyl-2H-azirinen an Azodicarbonsäure-diäthylester. 32. Mitteilung über Photoreaktionen31. Mitt., siehe [1]. (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1382-1392 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation of 2, 2-dimethyl-3-phenyl- (1a), 2, 3-diphenyl-2H-azirine (1b) or the azirine-precursors 1-azido-1-phenyl-propene (2a) and 1-azido-1-phenyl-ethylene (2b), respectively, in benzene in the presence of azodicarboxylic acid diethylester, yields the corresponding 1, 2-carbethoxy-3-phenyl-Δ3-1, 2, 4-triazolines 4a-d (Scheme 1).Refluxing 4 (a, c or d) in 0, 2-0, 4M aqueous ethanolic potassium hydroxide leads to the formation of the 1-carbethoxy-3-phenyl-Δ2-1, 2, 4-triazolines 6 (a, c or d). Under the same conditions 4b is converted to 3, 5-diphenyl-1, 2, 4-triazole (7b, Scheme 2). In 10M aqueous potassium hydroxide solution heating of either 4 (c or d) or 6 (c or d) yields the 3-phenyl-1, 2, 4-triazoles 7 (c or d).Photolysis of 1-carbethoxy-5, 5-dimethyl-3-phenyl-Δ2-1, 2, 4-triazoline (6a) in benzene in the presence of oxygen and trifluoroacetic acid methylester gives the 5-methoxy-2, 2-dimethyl-4-phenyl-5-trifluoromethyl-3-oxazoline (13, Scheme 5). 5, 5-Dimethyl-3-phenyl-1, 2, 4-triazole seems to be the intermediate, which on losing nitrogen gives the benzonitrile-isopropylide (3a).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570514
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  • 9
    Electronic Resource
    Electronic Resource
    Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen an Carbonsäurechloride. 35. Mitteilung über Photoreaktionen34. Mitt.: [1].Herrn Professor Otto Hoffmann-Ostenhof, Universität Wien, zum 60. Geburtstag gewidmet (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1393-1403 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation of 2, 3-diphenyl-2H-azirine (1a) and 1-azido-1-phenyl-propene, the precursor of 2-methyl-3-phenyl-2H-azirine (1b), in benzene, with a high pressure mercury lamp (pyrex filter) in the presence of acid chlorides yields the oxazoles 5a-d (Scheme 2). Photolysis of 2, 2-dimethyl-3-phenyl-2H-azirine (1c) under the same conditions gives after methanolysis the 5-methoxy-2, 2-dimethyl-4-phenyl-3-oxazolines 7a, b, d, while hydrolysis of the reaction mixture leads to the formation of the 1, 2-diketones 8a, c, d (Scheme 4). The suggested reaction path for all these reactions is a 1, 3-dipolar cycloaddition of the photochemically generated benzonitrilemethylides 2 to the carbonyl double bond of the acid chlorides to give the intermediates 4, followed by either elimination of hydrogen chloride or solvolysis (Schemes 2 and 4).Irradiation of 1c in the presence of acetic acid anhydride leads via the intermediate 9 to the 5-hydroxy-3-oxazoline 10 and the 5-methylidene-3-oxazoline 11 (Scheme 5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570515
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  • 10
    Electronic Resource
    Electronic Resource
    Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen mit Ketonen, Acylcyaniden und Ketoestern. 33. Mitteilung über Photoreaktionen32. Mitteilung siehe [1]. (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 2173-2192 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Similarly to aldehydes [6] ketones form 3-oxazolines via cyclo-addition to the benzonitrile-methylides 2 that arise photochemically from the 3-phenyl-2H-azirines 1. With various ketones benzonitrile-isopropylide (2a) gives cyclo-addition products in very good preparative yields (scheme 1). Benzonitrile-ethylide (2c) and benzonitrile-benzylide (2b) [8] react, however, sluggishly with ketones, smooth cyclo-addition being observed in their case only with «activated» ketones (2,2,2-trifluoro-acetophenone, 1,1,1-trifluoro-2-propanone). With 1a acetonyl-acetone forms the bis-adduct 12While the azirine 1a reacts with cyclohexanone to yield essentially only the spiro-(3-oxazoline) 13, it gives with cyclopentanone, depending on the reaction conditions, either the spiro-(3-oxazoline) 14 or the butenyl-3-oxazoline 15 (scheme 3). The formation of 15 has to be preceded by the photochemical formation of 4-pentenal from the ketone. Norcamphor and camphor react in a similar way (schemes 4 and 5).The azirines 1a-c react smoothly with the keto groups in acylcyanides and α-keto-esters, giving with the former 5-cyano-3-oxazolines and with the latter 5-ethoxycarbonyl-3-oxazolines (schemes 6 and 7).β-Keto-esters (acetoacetic ester) form with the dipole arising from 1a the expected addition product 31 and, via the protonated dipole d (scheme 8), finally the benzylidene-acetoacetic ester. Analogous results are obtained with malonodinitrile, trifluoro-acetamide and other weak acids such as alcohols [29] [30] (scheme 9).The light-induced rearrangement of the bicyclic isoxazoline 37 into the oxazoline 38 is visualized as an intramolecular cyclo-addition reaction (scheme 10). The cyclo-addition in this case proceeds with the aldehyde group inversed as compared to the related intermolecular benzonitrile-methylide addition to aldehydes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570732
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