title: Studies on synthetic approaches to 1H- and 2H-indazolyl derivatives.
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.
authors.affiliation: Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Isin
authors.forename: M
authors.initials: M
authors.lastname: de Jonge
authors.forename: N
authors.initials: N
authors.lastname: Castagnoli
mesh_terms: D007191:Indazoles / Q000138:chemical synthesis*; D015394:Molecular Structure; D013057:Spectrum Analysis
chemical_list: D007191:Indazoles