Indazole, tautomerism spectroscopy

A well-known example of non-prototropic tautomerism is that of azolides (acylotropy). The acyl group migrates between the different heteroatoms and the most stable isomer (annular or functional) is obtained after equilibration. In indazoles both isomers are formed, but 2-acyl derivatives readily isomerize to the 1-substituted isomer. The first order kinetics of this isomerization have been studied by NMR spectroscopy (74TL4421). The same publication described an experiment (Scheme 8) that demonstrated the intermolecular character of the process, which has been called a dissociation-recombination process. 

Tautomeric processes in some nitroindazoles, 6-nitroindazole-based complexes, and other nitrated indazoles have been investigated by vibration spectroscopy [583, 645, 655, 1080-1084],... 

Structure and reactivity of neutral pyrazole, its anion and its cation. 2.2 Structure and reactivity of substituted pyrazoles. 2.3 Structure and reactivity of indazoles. 2.4 Dipole moments Structural Methods. 3.1 X-Ray diffraction. 3.2 Microwave spectroscopy. 3.3 H NMR spectroscopy. 3.4 C NMR spectroscopy. 3.5 Nitrogen NMR spectroscopy 3.6 UV spectroscopy. 3.7 JR spectroscopy. 3.8 Mass spectrometry. 3.9 Photoelectron spectroscopy. 3.10 Electron spin resonance spectroscopy Thermodynamic Aspects. 4.1 Intermolecular forces. 4.2 Stability and stabilization. 4.3 Conformation and configuration Tautomerism... 

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