Cinnoline

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Cinnoline
Cinnoline numbering.png
C=black, H=white, N=blue Cinnoline-3D-balls.png
C=black, H=white, N=blue
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C=black, H=white, N=blue
Names
Preferred IUPAC name
Cinnoline [1]
Other names
Benzopyridazine
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.423 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C8H6N2/c1-2-4-8-7(3-1)5-6-9-10-8/h1-6H Yes check.svgY
    Key: WCZVZNOTHYJIEI-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C8H6N2/c1-2-4-8-7(3-1)5-6-9-10-8/h1-6H
    Key: WCZVZNOTHYJIEI-UHFFFAOYAA
  • n1nccc2ccccc12
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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Infobox references

Cinnoline is an aromatic heterocyclic compound with the formula C8H6N2. It is isomeric with other naphthyridines including quinoxaline, phthalazine and quinazoline.

Contents

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) upon cooling ethereal solutions. The free base melts at 39 °C. It has a taste resembling that of chloral hydrate and leaves a sharp irritation for some time. Cinnoline derivatives are obtained from oxycinnoline carboxylic acid, which is formed by digesting orthophenyl propiolic acid diazo chloride with water. Oxycinnoline carboxylic acid on heating gives oxycinnoline, melting at 225 °C, which with phosphorus pentachloride gives chlorcinnoline. This substance is reduced by iron filings and sulfuric acid to dihydrocinnoline. [3]

Discovery and synthesis

The compound was first obtained in impure form by cyclization of the alkyne o-C6H4(NH2)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:

Widman-Stoermer reaction Widman-stoermer-reaction.png
Widman–Stoermer reaction

The sodium nitrite is first converted to nitrous acid which then forms the electrophilic intermediate dinitrogen trioxide. The next intermediate is the stable nitrosamine with goes on to lose water forming the diazonium salt which then reacts with the vinyl group in the ring-closing step. A conceptually related reaction is the Bamberger triazine synthesis towards triazines.

Another cinnoline method is the Borsche cinnoline synthesis.

Safety

Cinnoline is toxic.[ citation needed ]

See also

Related Research Articles

Carboxylic acid Organic compound

A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.

Ester Chemical compounds consisting of a carbonyl adjacent to an ether linkage

An ester is a chemical compound derived from an acid in which at least one –OH hydroxyl group is replaced by an –O– alkyl (alkoxy) group, as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are fatty acid esters of glycerol; they are important in biology, being one of the main classes of lipids and comprising the bulk of animal fats and vegetable oils.

Ketone Class of organic compounds having structure RCOR

In chemistry, a ketone is a functional group with the structure R2C=O, where R can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond). The simplest ketone is acetone (R = R' = methyl), with the formula CH3C(O)CH3. Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone.

Acridine Chemical compound

Acridine is an organic compound and a nitrogen heterocycle with the formula C13H9N. Acridines are substituted derivatives of the parent ring. It is a planar molecule that is structurally related to anthracene with one of the central CH groups replaced by nitrogen. Like the related molecules pyridine and quinoline, acridine is mildly basic. It is an almost colorless solid, which crystallizes in needles. There are few commercial applications of acridines, at one time acridine dyes were popular but they are now relegated to niche applications, such as with acridine orange. The name is a reference to the acrid odour and acrid skin-irritating effect of the compound.

Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4H4NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme.

Quinoline Chemical compound

Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents. Quinoline itself has few applications, but many of its derivatives are useful in diverse applications. A prominent example is quinine, an alkaloid found in plants. Over 200 biologically active quinoline and quinazoline alkaloids are identified. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance.

Oxime

An oxime is a chemical compound belonging to the imines, with the general formula RR'C=NOH, where R is an organic side-chain and R' may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of amides with general structure R1C(=NOH)NR2R3.

Acyl halide Chemical compound

An acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

Cyclopropene is an organic compound with the formula C3H4. It is the simplest cycloalkene. Because the ring is highly strained, cyclopropene is difficult to prepare and highly reactive. This colorless gas has been the subject for many fundamental studies of bonding and reactivity. It does not occur naturally, but derivatives are known in some fatty acids. Derivatives of cyclopropene are used commercially to control ripening of some fruit.

Nitro compound

Nitro compounds are organic compounds that contain one or more nitro functional groups. The nitro group is one of the most common explosophores used globally. The nitro group is also strongly electron-withdrawing. Because of this property, C−H bonds alpha (adjacent) to the nitro group can be acidic. For similar reasons, the presence of nitro groups in aromatic compounds retards electrophilic aromatic substitution but facilitates nucleophilic aromatic substitution. Nitro groups are rarely found in nature. They are almost invariably produced by nitration reactions starting with nitric acid.

Gold(III) chloride Chemical compound

Gold(III) chloride, traditionally called auric chloride, is a compound of gold and chlorine with the molecular formula Au2Cl6. The "III" in the name indicates that the gold has an oxidation state of +3, typical for many gold compounds. Gold(III) chloride is hygroscopic and decomposes in visible light. This compound is a dimer of AuCl3. This compound has few uses, although it catalyzes various organic reactions.

Cyanuric chloride Chemical compound

Cyanuric chloride is an organic compound with the formula (NCCl)3. This white solid is the chlorinated derivative of 1,3,5-triazine. It is the trimer of cyanogen chloride. Cyanuric chloride is the main precursor to the popular but controversial herbicide atrazine.

Isatin Chemical compound

Isatin, also known as tribulin, is an organic compound derived from indole with formula C8H5NO2. The compound was first obtained by Otto Linné Erdman and Auguste Laurent in 1840 as a product from the oxidation of indigo dye by nitric acid and chromic acids.

Fluorene Chemical compound

Fluorene, or 9H-fluorene is an organic compound with the formula (C6H4)2CH2. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar. It is insoluble in water and soluble in many organic solvents. Although sometimes classified as a polycyclic aromatic hydrocarbon, the five-membered ring has no aromatic properties. Fluorene is mildly acidic.

Anthranilic acid Chemical compound

Anthranilic acid is an aromatic acid with the formula C6H4(NH2)(CO2H) and has a sweetish taste. The molecule consists of a benzene ring, ortho-substituted with a carboxylic acid and an amine. As a result of containing both acidic and basic functional groups, the compound is amphoteric. Anthranilic acid is a white solid when pure, although commercial samples may appear yellow. The anion [C6H4(NH2)(CO2)], obtained by the deprotonation of anthranilic acid, is called anthranilate. Anthranilic acid was once thought to be a vitamin and was referred to as vitamin L1 in that context, but it is now known to be non-essential in human nutrition.

The total synthesis of quinine, a naturally-occurring antimalarial drug, was developed over a 150-year period. The development of synthetic quinine is considered a milestone in organic chemistry although it has never been produced industrially as a substitute for natural occurring quinine. The subject has also been attended with some controversy: Gilbert Stork published the first stereoselective total synthesis of quinine in 2001, meanwhile shedding doubt on the earlier claim by Robert Burns Woodward and William Doering in 1944, claiming that the final steps required to convert their last synthetic intermediate, quinotoxine, into quinine would not have worked had Woodward and Doering attempted to perform the experiment. A 2001 editorial published in Chemical & Engineering News sided with Stork, but the controversy was eventually laid to rest once and for all when Williams and coworkers successfully repeated Woodward's proposed conversion of quinotoxine to quinine in 2007.

Schmidt reaction

The Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually a aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen. It is named after Karl Friedrich Schmidt (1887–1971), who first reported it in 1924 by successfully converting benzophenone and hydrazoic acid to benzanilide. Surprisingly, the intramolecular reaction was not reported until 1991 but has become important in the synthesis of natural products.

Phthalonitrile Chemical compound

Phthalonitrile is an organic compound with the formula C6H4(CN)2, which is an off-white crystal solid at room temperature. It is a derivative of benzene, containing two adjacent nitrile groups. The compound has low solubility in water but is soluble in common organic solvents. The compound is used as a precursor to phthalocyanine and other pigments, fluorescent brighteners, and photographic sensitizers.

4-Chlorophenyl azide Chemical compound

4-Chlorophenyl azide is an organic aryl azide compound with the chemical formula C6H4ClN3. The geometry between the nitrogen atoms in the azide functional group is approximately linear while the geometry between the nitrogen and the carbon of the benzene is trigonal planar.

3-Dimethylaminoacrolein Chemical compound

3-Dimethylaminoacrolein is an organic compound with the formula Me2NC(H)=CHCHO. It is a pale yellow water-soluble liquid. The compound has a number of useful and unusual properties, e.g. it "causes a reversal of the hypnotic effect of morphine in mice" and has a "stimulating effect in humans".

References

  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. 212. doi:10.1039/9781849733069. ISBN   978-0-85404-182-4.
  2. Brown, H.C., et al., in Baude, E.A. and Nachod, F.C., Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955.
  3. Wikisource-logo.svg One or more of the preceding sentences incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Cinnolin". Encyclopædia Britannica . Vol. 6 (11th ed.). Cambridge University Press. p. 377.
  4. Victor von Richter (1883). "Über Cinnolinderivate". Chemische Berichte. 16: 677–683. doi:10.1002/cber.188301601154.
  5. 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.
  6. Bradford P. Mundy; Michael G. Ellerd; Frank G. Jr. Favaloro (2005). Name Reactions and Reagents in Organic Synthesis. ISBN   0-471-22854-0.