Cinnoline-4-carboxylic acid, preparation

The Co(II), Ni(II), Fe(II), and Cu(II) complexes of 4-amino-3-cinnoline-carboxylic acid and 4-amino-7-chloro-6-fluoro-3-cinnolinecarboxylic acid have been prepared and characterized. ... 

The first synthesis of cinnoline was reported by von Richter in 1883. The diazonium chloride 5 which was obtained from o-aminophenylpropiolic acid (4), was heated in water at 70°C to provide the 4-hydroxycinnoline-3-carboxylic acid (6). When this acid 6 was heated above its melting point, carbon dioxide was liberated and 4-hydroxycinnoline (7) was obtained. Distillation of 4-hydroxycinnoline (7) with zinc dust furnished a small amount of oil, which was assumed to be cinnoline (8). The preparation of 4-hydroxycinnoline (7) was repeated by Busch and Klett, although in lower yield when compared to the original report. Busch and Rast later converted the 4-hydroxycinnoline (7) successfully to cinnoline (8) via the 4-chlorocinnoline (9). ... 

Benzo[c] cinnoline aldehydes are as yet unknown. The 2- and 3-acetyl derivatives have been prepared, but the majority of known compounds relevant to this section are mono- and dicarboxylic acid derivatives. These include the 2-, - - 3-, ° and 4. - o2.J55,i57 monoacids and esters, the lactone of 10-hydroxybenzo[c]cinnoline-l-carboxylic acid, some halogeno- and methyl-substituted 2- and 4. carboxylic acids, and the 2,9-, 3,8-, - - and 4,7- dicarboxylic acids and derivatives. These compounds have been obtained by ring synthesis, or, in the case of 2-methylbenzo[c]dnnoline-9-carboxylic acid, by side-chain oxidation, " rather than by the introduction of substituents into benzo[c] cinnoline. Benzo[c]cinnoline-l-carbonitrile has been prepared, albeit in low... 

Preparation of Carboxylic Acid Chlorides (and Anhydrides). Oxalyl chloride has found general application for the preparation of carboxylic acid chlorides since the reagent was introduced by Adams and Ulich. Acid chlorides produced by this means have subsequently featured in the synthesis of acyl azides, bromoalkenes, carboxamides, cinnolines, diazo ketones, (thio)esters, lactones, ketenes for cycloaddition reactions, intramolecular Friedel-Crafts acylation reactions, and the synthesis of pyridyl thioethers. ... 

Unsubstituted 7-oxo-l,2,3,7-tetrahydropyrido[3,2,l-i ]cinnoline-8-carboxylates were A-alkylated with dialkyl sulfates, and they were also A-acylated with acetic anhydride in acetic acid to give the 1-substituted derivatives (92EUP470578). The 1-hydroxymethyl derivatives were prepared from the 1-unsubstituted compound with formalin in acetic acid. 

This chapter deals with nuclear and extranuclear cinnolinecarboxylic acids and the corresponding carboxylic esters, acyl halides, carboxamides, carbohydrazides, carbonitriles, and carbaldehydes, and the ketonic acylketones. To avoid repetition, the interconversion of these cinnoline derivatives are discussed only at the first opportunity for example, the esterification of cinnolinecarboxylic acids is covered as a reaction of cinnolinecarboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on acids precedes that on esters. To avoid any confusion, appropriate cross-references have been included. 

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