Quinoline-2-carboxylic acids aromatization with

This is an example of the Doebner synthesis of quinoline-4-carboxylic acids (cinchoninic acids) the reaction consists in the condensation of an aromatic amine with pyruvic acid and an aldehj de. The mechanism is probably similar to that given for the Doebner-Miller sj nthesis of quinaldiiie (Section V,2), involving the intermediate formation of a dihydroquinoline derivative, which is subsequently dehydrogenated by the Schiff s base derived from the aromatic amine and aldehyde. 

Esters of 9-oxo-6,9-dihydro-triazolo[4,5-/]quinoline-8-carboxylic acids 176 can be hydrolyzed and decarboxylated to afford the 9-oxo-6,9-dihydrotriazolo[4, 5-/]quinolines 177 (Scheme 55) (87CCC2918, 88CCC1068,90JMC2640). These in turn were aromatized with POCI3 to the appropriate 9-chloroderivatives 178,... 

The decarboxylation of aromatic acids is most often carried out by heating with copper and quinoline. However, two other methods can be used with certain substrates. In one method, the salt of the acid (ArCOO ) is heated, and in the other the carboxylic acid is heated with a strong acid, often sulfuric. The latter method is accelerated by the presence of electron-donating groups in ortho and para positions and by the steric effect of groups in the ortho positions in benzene systems it is... 

Several polynuclear aromatic hydrocarbons may be synthesized by procedures involving decarboxylation. The dry distillation of 3-phe-nanthrylacetic acid and powdered soda lime furnishes the best method of synthesis of 3-methylphenanthrene (84%). Heating aryl carboxylic acids with copper powder or copper oxide in quinoline or quinaldine is also an effective method of decarboxylation. ... 

Aromatic 0-hydroxy carboxylic acids behave very similarly to fi-oxo carboxylic acids they sometimes lose carbon dioxide when merely boiled with water, but this is a general reaction when they are heated with pyridine, quinoline, aniline, or dimethylaniline. This behavior can certainly be ascribed to reaction of aromatic 0-hydroxy acids as the keto tautomer ... 

Of the aromatic dibasic acids, the three phthalic acids on treatment with hydrazoic acid yield the corresponding aminobenzoic acids with mere traces of the diaminobenzenes. > Anthranilic acid and its derivatives in which one hydrogen on the amino group is replaced by acetyl, benzoyl, or p-toluyl are inert to hydrazoic acid. These compounds thus resemble in activity a-amino acids and their derivatives in the aliphatic series. The following pyridine and quinoline acids resemble -amino acids and also do not react pyridine-2-carboxylic acid, pyridine-2,3-... 

It has long been known that aromatic acids undergo decarboxylation to produce arenes when rigorously heated in the presence of copper and quinoline [73]. This reaction would involve decarboxylation of a copper carboxylate intermediate. A more explicit example has been reported with copper pentafluoroben-zoate (Scheme 1.57) [74]. When copper(I) pentafluorobenzoate was heated at 60 C in quinoline, pentafluorophenylcopper was produced with liberation... 

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