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Photochemische Synthese von 4-Phenyl-3-oxazolin-5-onen und deren thermische Dimerisierung


Gakis, Nikolas; Märky, Michael; Hansen, Hans-Jürgen; Heimgartner, Heinz; Schmid, Hans; Oberhänsli, Willi E (1976). Photochemische Synthese von 4-Phenyl-3-oxazolin-5-onen und deren thermische Dimerisierung. Helvetica Chimica Acta, 59(6):2149-2167.

Abstract

Irradiation of 3-phenyl-2H-azirines affords reactive benzonitrile-methylide intermediates, which can be trapped by carbon dioxide to yield 4-phenyl-3-oxazolin-5-ones (Scheme 1). The first section of the paper deals with the experimental description of this reaction, which already has been preliminarily communicated. Upon irradiation the 3-oxazolin-5-ones undergo photoextrusion of carbon dioxide to reform the corresponding benzonitrile-methylides, which can be trapped by dimethyl acetylenedicarboxylate. In the second section of the paper, reactions of 2-methyl-4-phenyl-3-oxazolin-5-one (3c) are described. Upon heating to 130°, this compound is partially converted to 2-methyl-4-phenyl-2-oxazolin-5-one (azlactone 4e). Prolonged heating of 3c affords the dimer 7 (Scheme 3) as well as the imidazole derivative 9 (Scheme 4). Compound 7 is related to the ‘Rügheimer compound’ C18H14N2O4, formed from hippuric acid methylester. The structure of 7 was determined by X-ray crystallography and this supports the formula assigned earlier to the ‘Rügheimer compound’ (12) and related pyrrolidin-2,4-diones. The possible mechanism of the thermal formation of 7, which is also base catalysed, is represented in Scheme 3, the one for the formation of the imidazol 9 in Scheme 4. Under the influence of oxygen the 2,4-diphenyl-3-oxazolin-5-one (3b) undergoes a dehydro-dimerization to yield compound 16 (Scheme 7). Section three contains the structure elucidation of compound 16 and a mechanistic proposal for the formation of the pyrazine 19 upon thermolysis of 2,4-diphenyl-2-oxazolin-5-one (4b, Scheme 7).

Abstract

Irradiation of 3-phenyl-2H-azirines affords reactive benzonitrile-methylide intermediates, which can be trapped by carbon dioxide to yield 4-phenyl-3-oxazolin-5-ones (Scheme 1). The first section of the paper deals with the experimental description of this reaction, which already has been preliminarily communicated. Upon irradiation the 3-oxazolin-5-ones undergo photoextrusion of carbon dioxide to reform the corresponding benzonitrile-methylides, which can be trapped by dimethyl acetylenedicarboxylate. In the second section of the paper, reactions of 2-methyl-4-phenyl-3-oxazolin-5-one (3c) are described. Upon heating to 130°, this compound is partially converted to 2-methyl-4-phenyl-2-oxazolin-5-one (azlactone 4e). Prolonged heating of 3c affords the dimer 7 (Scheme 3) as well as the imidazole derivative 9 (Scheme 4). Compound 7 is related to the ‘Rügheimer compound’ C18H14N2O4, formed from hippuric acid methylester. The structure of 7 was determined by X-ray crystallography and this supports the formula assigned earlier to the ‘Rügheimer compound’ (12) and related pyrrolidin-2,4-diones. The possible mechanism of the thermal formation of 7, which is also base catalysed, is represented in Scheme 3, the one for the formation of the imidazol 9 in Scheme 4. Under the influence of oxygen the 2,4-diphenyl-3-oxazolin-5-one (3b) undergoes a dehydro-dimerization to yield compound 16 (Scheme 7). Section three contains the structure elucidation of compound 16 and a mechanistic proposal for the formation of the pyrazine 19 upon thermolysis of 2,4-diphenyl-2-oxazolin-5-one (4b, Scheme 7).

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Additional indexing

Other titles:Photochemical Synthesis of 4-Phenyl-3-oxazolin-5-ones and their Thermal Dimerization
Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:German
Date:1976
Deposited On:05 Nov 2014 10:25
Last Modified:21 Nov 2017 17:31
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0018-019X
Funders:Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung
Publisher DOI:https://doi.org/10.1002/hlca.19760590626

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