Indazole

Indazole
Names
	Preferred IUPAC name 1H-Indazole
Identifiers
CAS Number	271-44-3 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:36670 ;
ChEMBL	ChEMBL86795 ;
ChemSpider	8866 ;
ECHA InfoCard	100.005.436
PubChem CID	9221;
UNII	7C4VQE5C03 ;
CompTox Dashboard (EPA)	DTXSID4075374 ;
	InChI InChI=1S/C7H6N2/c1-2-4-7-6(3-1)5-8-9-7/h1-5H,(H,8,9) Key: BAXOFTOLAUCFNW-UHFFFAOYSA-N ; InChI=1/C7H6N2/c1-2-4-7-6(3-1)5-8-9-7/h1-5H,(H,8,9) Key: BAXOFTOLAUCFNW-UHFFFAOYAQ;
	SMILES c2ccc1[nH]ncc1c2;
Properties
Chemical formula	C7H6N2
Molar mass	118.14 g/mol
Melting point	147 to 149 °C (297 to 300 °F; 420 to 422 K)
Boiling point	270 °C (518 °F; 543 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[2]

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 L. (black cumin). Nigeglanine was isolated from extracts of Nigella glandulifera.

The Davis–Beirut reaction can generate 2H-indazoles.^[3]

Indazole, C₇H₆N₂, was obtained by E. Fischer (Ann. 1883, 221, p. 280) by heating ortho-hydrazine cinnamic acid,^[4]

^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 213. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
^ Catalan, Javier; Elguero, Jose (1987). "Basicity and Acidity of Azoles". Advances in Heterocyclic Chemistry Volume 41. Vol. 41. Elsevier. pp. 187–274. doi:10.1016/s0065-2725(08)60162-2. ISBN 9780120206414.
^ Zhu, Jie S.; Haddadin, Makhluf J.; Kurth, Mark J. (22 July 2019). "Davis–Beirut Reaction: Diverse Chemistries of Highly Reactive Nitroso Intermediates in Heterocycle Synthesis". Accounts of Chemical Research. 52 (8): 2256–2265. doi:10.1021/acs.accounts.9b00220. PMC 6702092. PMID 31328502.
^ Chisholm, Hugh, ed. (1911). "Indazoles" . Encyclopædia Britannica. Vol. 14 (11th ed.). Cambridge University Press. p. 371.

[1] International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 213. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.

[2] Catalan, Javier; Elguero, Jose (1987). "Basicity and Acidity of Azoles". Advances in Heterocyclic Chemistry Volume 41. Vol. 41. Elsevier. pp. 187–274. doi:10.1016/s0065-2725(08)60162-2. ISBN 9780120206414.

[3] Zhu, Jie S.; Haddadin, Makhluf J.; Kurth, Mark J. (22 July 2019). "Davis–Beirut Reaction: Diverse Chemistries of Highly Reactive Nitroso Intermediates in Heterocycle Synthesis". Accounts of Chemical Research. 52 (8): 2256–2265. doi:10.1021/acs.accounts.9b00220. PMC 6702092. PMID 31328502.

[4] Chisholm, Hugh, ed. (1911). "Indazoles" . Encyclopædia Britannica. Vol. 14 (11th ed.). Cambridge University Press. p. 371.

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