The structure of indazolinone and derivatives in the solid state and in solution: an X-ray and nuclear magnetic resonance study

The structure of indazolinone and some of its derivatives was obtained by the combined use of crystallography, 13C CP/MAS, and 15N n.m.r. It was concluded that indazolinone exists as such in the solid state but only as a minor tautomer (15%) in DMSO solution, where the 3-hydroxyindazole tautomer predominates (85%). The result of bromination of indazolinone is reported. Two acylhydrazines, as open analogues of indazolinone, were studied as model compounds.