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2005
Fused pyridine derivatives
R 0450
Ring Closure Reactions of 3-Arylhydrazonoalkyl-quinolin-2-ones to 1-Aryl-pyra— The reactivity of the key intermediates of type (III), ob07- 136 zolo[4,3-c]quinolin-2-ones.
tained as arylhydrazones with hydroxy groups, (III), with toluenesulfonyloxy groups,
(VII), and chloro substituents as leaving groups, is examined by differential scanning
calorimetry. The data obtained from this method, reaction temperature and reaction enthalpy, are valuable for the planning of thermolysis reactions. The best conditions for
cyclization of (III) can be deducted from DSC data, performing the thermolysis of (III)
in acidic medium using acetic acid as solvent and concentrated sulfuric acid as strong
acidic catalyst. Similarly, the synthesis of pyrazoloquinolinones (IVa) and (IVb) by
thermolysis of tosyloxy compounds (VII) furnishes better results according to the DSC
data. — (STADLBAUER*, W.; HOJAS, G.; J. Heterocycl. Chem. 41 (2004) 5,
681-690; Dep. Chem., Karl-Franzens-Univ., A-8010 Graz, Austria; Eng.) —
H. Hoennerscheid
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