Oxidation of 3-substituted 4-R-6-nitro-1-phenyl-1H-indazoles and benzo[d]isoxazoles (R = Ph, CH2CO2Me) gave the corresponding sulfones treatment of which with PhSH-K2CO3 in N-methylpyrrolidone results in replacement of only the RSO2 group in position 4 with the 6-NO2 group remaining intact, contrary to the known sequence of nucleophilic substitution for meta-arranged nucleofuges.
A method for the synthesis of 1-aryl-3-formyl-4,6-dinitro-1H-indazoles by the reaction of picrylacetaldehyde with aryldiazonium salts followed by intramolecular cyclization of the resulting picrylglyoxal monoarylhydrazones was developed. Various 4,6-dinitro-1-phenyl-1H-indazoles substituted in position 3 were prepared via transformations involving the formyl group of 3-formyl-4,6-dinitro-1-phenyl-1H-indazole. 3-R-4,6-Dinitro-1-phenyl-1H-indazoles (R = CHO, CN, 1,3-dioxolan-2-yl) react regiospecifically with anionic O-, S-, and N-nucleophiles, in particular, with replacement of only the 4-NO2 group. Thus previously unknown 3-R-4-Nu-6-nitro-1-phenyl-1H-indazoles were synthesized (Nu is a nucleophile residue).