Synthesis and transformations of perfluoroalkyl-containing 6,7-dihydro-1H-indazol-4(5H)-ones oximes

Abstract

Refluxing 3-perfluoroalkyl-6,7-dihydro-1Н-indazol-4(5Н)-ones with 4-fold excess of hydroxylamine hydrochloride in pyridine afforded their (E)-oximes. The obtained oximes were alkylated with ethyl iodide and acylated with carboxylic acids chlorides to obtain (E)-О-alkyl-and (E)-О-acyloximes respectively. Heating oximes in PPA at 120°С results in their aromatization by Semmler-Wolff reaction, hydrolysis of perfluoroalkyl groups, and generation of 4-amino-1-aryl-5,6-dimethyl-1Н-indazole-3-carboxylic acids from of 3-tri-fluoromethylindazolone oximes and 1-(4-amino-1-aryl-5,6-dimethyl-1Н-indazol-3-yl)fluoroalkan-1-ones from of 3-perfluoroethyl-and 3-perfluoropropylindazolone oximes.