- Unusual Reactions between Some 1-Aroyl-4,5-dihydro-4,4-dimethyl-5-methylene-1H-pyrazoles and Ketenes
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5-Methylene-4,5-dihydropyrazoles 1a-d react with diphenylketene (DPK), affording the pyrazolyl-3,3-diphenyl-2-propenyl benzoates 2a-d, very likely via the corresponding pyrazolyl-enol esters 7 as intermediates.By acid hydrolysis of 2 the (diphenyloxopropyl)pyrazole derivative 3 in its enol form is isolated, whereas by cycloaddition with 4-methylbenzonitrile oxide the spiro compound 4 is obtained. 5-Methylene-4,5-dihydropyrazoles 1a-c and 1g also react with dichloroketene (DCK) to give the corrresponding 5-hydroxypyrazolines 5.The structure of 2b has also been confirmed by X-ray crystallography.
- Mitkidou, Sophia,Papadopoulos, Stelios,Stephanidou-Stephanatou, Julia,Terzis, Aristides,Mentzafos, Demetrios
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p. 4732 - 4735
(2007/10/02)
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- Oxidation of Bis-aroylhydrazones of 3,3-Dimethylpentane-2,4-dione and Thermal Decomposition of the Oxidation Products (1)
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Oxidation of the title bis-aroylhydrazones 2 with lead tetraacetate gives 1-aroyl-5-aroylazo-3,4,4,5-tetramethyl-2-pyrazolines 6 in good yields.The aroylazopyrazolines 6 decompouse by refluxing in chloroform of ethanol solution to 1-aroyl-5-hydroxy-3,4,4,5-tetramethyl-2-pyrazolines 3, 1-aroyl-5-methylene-3,4,4-trimethyl-2-pyrazoles 10 and 1-aroyl-3,4,4,5-tetramethyl-2-pyrazolines 11.The spectral data of the, prepared compounds, as well as the reaction mechanisms are discussed.
- Stephanidou-Stephanatou, J.
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p. 845 - 853
(2007/10/02)
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