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Indazole, also called isoindazole, is a heterocyclic aromatic organic compound. This bicyclic compound consists of the fusion of benzene and pyrazole.
Indazole is an amphoteric molecule which can be protonated to an indazolium cation or deprotonated to an indazolate anion. The corresponding ''pKa'' values are 1.04 for the equilibrium between indazolium cation and indazole and 13.86 for the equilibrium between indazole and indazolate anion.
Indazole derivatives display a broad variety of biological activities.
Indazoles are rare in nature. The alkaloids nigellicine, nigeglanine, and nigellidine are indazoles. Nigellicine was isolated from the widely distributed plant ''
Nigella sativa
''Nigella sativa'' (black caraway, also known as black cumin, nigella, kalonji or siyahdaneh) is an annual flowering plant in the family Ranunculaceae, native to eastern Europe (Bulgaria and Romania) and Western Asia (Cyprus, Turkey, Iran and Ir ...
'' L. (black cumin). Nigeglanine was isolated from extracts of ''Nigella glandulifera
''Nigella'' is a genus of 18 species of annual plants in the family Ranunculaceae, native to Southern Europe, North Africa, South Asia, Southwest Asia and Middle East. Common names applied to members of this genus are nigella, devil-in-a-bush o ...
''.
The Davis–Beirut reaction can generate 2''H''-indazoles.
Indazole, C7H6N2, was obtained by E. Fischer (''Ann.'' 1883, 221,
p. 280) by heating ortho-hydrazine cinnamic acid,
:
Some derivatives
; indazole-3-carboxylic acid: Having acarboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
group on carbon 3. Can be further modified to lonidamine.
See also
* Indole, an analog with only one nitrogen atom in position 1. * Benzimidazole, an analog with the nitrogen atoms in positions 1 and 3. *Simple aromatic ring
Simple aromatic rings, also known as simple arenes or simple aromatics, are aromatic organic compounds that consist only of a conjugated planar ring system. Many simple aromatic rings have trivial names. They are usually found as substructures of ...
s
* 7-Nitroindazole
7-Nitroindazole, or 7-NI, is a heterocyclic small molecule containing an indazole ring that has been nitrated at the 7 position. Nitroindazole acts as a selective inhibitor for neuronal nitric oxide synthase, a hemoprotein enzyme that, in neuron ...
, an indazole-based nitric oxide synthase inhibitor
References
* Synthesis: W. Stadlbauer, in ''Science of Synthesis'' 2002, ''12'', 227, and W. Stadlbauer, in ''Houben-Weyl'', 1994, ''E8b'', 764. * Review: A. Schmidt, A. Beutler, B. Snovydovych, ''Recent Advances in the Chemistry of Indazoles'', ''Eur. J. Org. Chem.'' 2008, 4073 – 4095. {{Nitric oxide signaling Simple aromatic rings