Heterocycle synthesis Skraup quinoline

Finally, some results obtained from indazoles substituted in the carbocycle are of interest, even though in these cases the reaction does not involve the heterocyclic moiety (Section 4.04.2.3.2(ii)). For example, pyrazolo[3,4-/]- (566) and pyrazolo[4,3-/]-quinolines (567) have been obtained from aminoindazoles by the Skraup synthesis (76JHC899). Diethylethoxy-methylenemalonate can also be used to give (566 R = C02Et, R = OH) (77JHC1175). Pyrazolo-[4,3-/]- and -[4,3-g]-quinazolones (568) and (569) have been obtained from the reaction of formamide with 5-amino-4-methoxycarbonyl- and 6-amino-5-carboxyindazole, respectively (81CB1624). 

As the amino component can be varied in many ways, the Skraup synthesis is widely applicable to the preparation of quinolines unsubstituted in the heterocyclic moiety and especially to the preparation of polyheterocycles. This is illustrated by the synthesis of 1,10-phenanthroline 86, a much-used chelating ligand, starting from 8-aminoquinoline ... 

Quinolines, heterocyclic compounds that contain a pyridine ring fused to a benzene ring, are commonly synthesized by a method known as the Skraup synthesis, in which aniline reacts with glycerol under acidic conditions. Nitrobenzene is added to the reaction mixture to serve as an oxidizing agent. The first step in the synthesis is the dehydration of glycerol to propenal. 

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