Trifluoro‐3‐hydroxy‐1H‐indazolecarboxylic Acids and Esters from Perfluorinated Benzenedicarboxylic Acids

Abstract

AbstractTwelve new 3‐hydroxyindazoles, each bearing three fluorine substituents and a CO2R group (R = H, CH3, C2H5) distributed around its 4‐, 5‐, 6‐, and 7‐positions, have been synthesized. They were studied by NMR in solution (1H, 13C, 15N, 19F) and in the solid state (13C, 15N). In solution, all of them are 3‐hydroxy tautomers: the a form. In the solid state, although the 3‐hydroxy tautomers are still the most frequent, there are some cases of indazolin‐3‐ones – the b form – and one example (12ab) of the very rare case in which both tautomers are present.