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Updated: Aug 8, 2026

Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
Studies on synthetic approaches to 1H- and 2H-indazolyl derivatives
E M Isin1, M de Jonge, N Castagnoli
1Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
Abstract:
Synthetic approaches designed to provide 1H- and 2H-indazolyl derivatives of potential biological interest are reported. Special emphasis has been placed on the characterization of indazolylpyridinium products generated from reactions between indazole and 4-chloro-1-methylpyridinium iodide under various conditions. A stable mixture consisting of 3 parts of the 1H-isomer 9 to 1 part of the 2H-isomer 10 was obtained at room temperature in the presence of the base 2,2,6,6-tetramethylpiperidine (TMP). The same reaction at 60 degrees C gave only the 1H-isomer 9. At 100 degrees C in the absence of TMP only the 2H-isomer 10 was formed. The isomerization of 10 to 9 was found to proceed quantitatively at 60 degrees C but only in the presence of TMP. The effects of temperature and base on the course of these reactions are rationalized in terms of kinetic and thermodynamic parameters.
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