Thermal transformation of cyclopropylazoarenes into the five-membered nitrogen-containing heterocycles |
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Authors: | R A Novikov I P Klimenko E V Shulishov V A Korolev Yu V Tomilov |
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Institution: | (1) N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation |
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Abstract: | Cyclopropylazoarenes containing methoxy groups in the aromatic ring give the corresponding N-arylpyrazolines on the reflux in o-dichlorobenzene or on SnCl2 catalysis at 80 °C in good yields. The products can be smoothly oxidized into the corresponding pyrazoles. Thermolysis of
cyclopropylazoarenes containing hydroxy groups in the aromatic ring proceeds more complicated. Thus in the case of resorcin
azo derivative, strong resinification of the reaction mixture is observed and the corresponding N-arylpyrazoline is isolated only in −40% yield. Under similar conditions, thermolysis of 1-cyclopropyl- and 1-(1-methylcyclopropyl)azo-2-naphthol
proceeds otherwise and unexpectedly leads to naphtho1,2-d]oxazole derivatives with degradation of the cyclopropane ring.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1686–1692, August, 2008. |
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Keywords: | cyclopropylazoarenes thermolysis N-arylpyrazolines N-arylpyrazoles naphtho[1 2-d]oxazoles heterocyclization |
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