The Structures of Indazolin‐3‐one (=1,2‐Dihydro‐3H‐indazol‐3‐one) and 7‐Nitroindazolin‐3‐one

Abstract

The existence of polymorphism in parent indazolin‐3‐one (=1,2‐dihydro‐3H‐indazol‐3‐one; 1) is reported as well as an X‐ray and NMR CPMAS study establishing that its 7‐nitro derivative 2 exists as the 3‐hydroxy tautomer. Absolute shieldings calculated at the GIAO/B3LYP/6‐311++G(d,p) level were used to determine the tautomeric oxo/hydroxy equilibrium in solution, i.e., always the 1H‐indazol‐3‐ol tautomer predominates.

Polymorphism and Desmotropy in Heterocyclic Crystal Structures

“…Other examples are gathered in Chart : 4-aminopyrazole ( 37 ), diiminoisoindoline (a conformational isomorph with a 50:50 mixture of 38b and 38c and a conformational polymorph containing only 38b ), sibenadet ( 39 ) (three polymorphs) . 1,2,4-Triazino[2,3- a ]benzimidazol-5(4)H-3-ones ( 40 ) present polymorphism but both polymorphs contain the 5 H -tautomer ( 40b ), and indazolin-3-one ( 41 ) has two polymorphs of tautomer 41a …”

“…With the rapid increase of cocrystals and coformers (also called counter-molecules, where one component is molecular and a solid at room temperature), problems of desmotropy should appear, for instance, tautomer a with a coformer c and tautomer b with the same coformer. Maybe even 12a could be considered a cocrystal formed by two tautomers as well as the examples of Chart .…”

Crystal structure, DFT calculations and Hirshfeld surface analysis of 3-(4-methylphenyl)-6-nitro-1H-indazole

“…Of these, only seven are nitro derivatives. These are 3,7-dinitroindazole (Cabildo et al, 2011), two determinations of 7-nitroindazole (Ooms et al, 2000;Sopková -de Oliveira Santos et al, 2000), 7-nitro-1H-indazol-3-ol (Claramunt et al, 2009), 3-(4-methylphenyl)-6-nitro-1H-indazole (Liu et al, 2014) and 5-nitro-3thiomorpholino-1H-indazole and 5-nitro-3-(4-methylpiperaz-…”

Five‐Membered Heterocycles: 1,2‐Azoles. Part 1. Pyrazoles

“…In the field of neuroprotective activity, studies carried out by Wolff and Gribin [74] on inhibition of nitric oxide synthase by indazole agents confirmed the proposal that 5-nitro-, 6-nitro-and 7-nitroindazoles exert inhibitory actions by interaction of nitric oxide synthase such that oxygen does not bind. 7-Nitroindazole (38), a selective inhibitor of neuronal nitric oxide synthase, has been studied for neuroprotective activity and has been used to investigate the role of nitric oxide [75][76][77]. …”