Benzopyridines quinolines

There are two neutral benzopyridines, quinoline (benzo[6]pyridine) and isoquinotine (benzo[c]pyridine), together with the quinolizinium cation (benzo[a]pyridinium) (Box 3.1), formed by a ring fusion that utilizes the nitrogen atom. 

Small amounts of the benzopyridines quinoline and isoquinoline are excreted as their N-oxides (41) by guinea-pigs and are also formed by guinea-pig and rabbit hepatic microsomes15,28. Moreover, the antimalarial agent chloroquine affords an N-oxide as a metabolite of the quinoline ring system104. 

PYRIDINE DERIVATIVES AND RELATED COMPOUNDS (BENZOPYRIDINES = QUINOLINES)... 

Pyridine Derivatives and Related Compounds (Benzopyridines = Quinolines)... 

The azanaphthalenes (benzopyridines) quinoline and isoquinoline contain an electron-poor pyridine ring, susceptible to nucleophilic attack, and an electron-rich benzene ring that enters into electrophilic aromatic substitution reactions, usually at the positions closest to the heterocyclic unit. 

Quinoline and isoquinoline are benzopyridines. They behave by showing the reactivity associated with either the benzene or the pyridine rings. 

Perhaps the most significant benzopyridine fungicides are the normal metal chelate compounds derived from 8-hydroxyquinoline (33), itself manufactured from quinoline by sulfonation/caustic fusion. Applications of (33) have been reviewed (56CRV217). Related compounds include quinacetol sulfate (34) (B-77MI20901) and halacrinate (35) (B-77MI20901). 

Quinoline and isoquinoline, known as benzopyridines, are two isomeric heterocyclic compounds that have two rings, a benzene and a pyridine ring, fused together. In quinoline this fusion is at C2/C3, whereas in isoquinoline this is at C3/C4 of the pyridine ring. Like benzene and pyridine, these benzopyridines are also aromatic in nature. 

Benzopyridines are attacked by organometallic compounds at a position a to the nitrogen unless both a-positions are blocked. The dihydro derivatives of quinoline and isoquinoline are more stable and less easily aromatized than those from pyridine, and are hence more frequently isolated. 

Quinoline and isoquinoline are known as benzopyridines because they have both a benzene ring and a pyridine ring. Like benzene and pyridine, they are aromatic compounds. The pK values of their conjugate acids are similar to the pK of the conjugate acid of pyridine. (In order for the carbons in quinoline and isoquinoline to have the same numbers, the nitrogen in isoquinoline is assigned the 2-position, not the lowest possible number.)... 

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