Cinnoline
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| Names | |||
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| Preferred IUPAC name
Cinnoline[1] | |||
| Other names
Benzopyridazine
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| Identifiers | |||
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3D model (JSmol)
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| 1126565 | |||
PubChem CID
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| Properties | |||
| C8H6N2 | |||
| Molar mass | 130.150 g·mol−1 | ||
| Melting point | 39 °C (102 °F; 312 K) | ||
| Acidity (pKa) | 2.64[2] | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Template:Chembox Footer/trackingTemplate:Short description
Cinnoline is an aromatic heterocyclic compound with the formula C8H6N2. It is isomeric with other naphthyridines including quinoxaline, phthalazine and quinazoline. Neither the unsubstituted heterocycle nor any derivatives is known to occur naturally.[3]
Properties
The free base can be obtained as an oil by treatment of the hydrochloride with base. It co-crystallizes with one molecule of ether as white silky needles, (m.p. 24–25 °C or 75.2–77.0 °F) upon cooling ethereal solutions. The free base melts at 39 °C or 102.2 °F. It has a taste resembling that of chloral hydrate and leaves a sharp irritation for some time.
Discovery and synthesis
The compound was first obtained in impure form by cyclization of the alkyne o-C6H4(N2Cl)C≡CCO2H in water to give 4-hydroxycinnoline-3-carboxylic acid. This material could be decarboxylated and the hydroxyl group reductively removed to give the parent heterocycle. This reaction is called the Richter cinnoline synthesis.[4]
Improved methods exist for its synthesis. It can be prepared by dehydrogenation of dihydrocinnoline with freshly precipitated mercuric oxide. It can be isolated as the hydrochloride.[5]
Cinnolines are cinnoline derivatives. A classic organic reaction for synthesizing cinnolines is the Widman–Stoermer synthesis,[6] a ring-closing reaction of an α-vinyl- aniline with hydrochloric acid and sodium nitrite:
A conceptually related reaction is the Bamberger triazine synthesis towards triazines.
Another cinnoline method is the Borsche cinnoline synthesis.
Safety
Cinnoline is toxic.[3]
See also
References
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- ^ Page Module:Citation/CS1/styles.css has no content.International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 212. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
- ^ Page Module:Citation/CS1/styles.css has no content.Brown, H.C.; et al. (1955). Baude, E.A.; Nachod, F.C. (eds.). Determination of Organic Structures by Physical Methods. New York: Academic Press.
- ^ a b Page Module:Citation/CS1/styles.css has no content.Prashanthi Evangelin; Sasi Gold; Elisha; Radhika; Krishna Vamsi; Arathi (January 2020). "A Concise Review on Cinnolines". Innovative Journal of Medical and Health Science. 10 (04): 897–901.
- ^ Page Module:Citation/CS1/styles.css has no content.Victor von Richter (1883). "Über Cinnolinderivate". Chemische Berichte. 16: 677–683. doi:10.1002/cber.188301601154.
- ^ Page Module:Citation/CS1/styles.css has no content.Parrick, J.; Shaw, C. J. G.; Mehta, L. K. (2000). "Pyridazines, cinnolines, benzocinnolines and phthalazines". Rodd's Chemistry of Carbon Compounds. Vol. 4 (2nd ed.). pp. 1–69.
- ^ Page Module:Citation/CS1/styles.css has no content.Bradford P. Mundy; Michael G. Ellerd; Frank G. Jr. Favaloro (2005). Name Reactions and Reagents in Organic Synthesis. ISBN 0-471-22854-0.
