GB450842A - Manufacture of 2-methyl-3-hydroxy-quinoline-4-carboxylic acids - Google Patents

Abstract

2-Methyl-3-oxyquinoline-4-carboxylic acids are prepared by reacting a halogenacetone with a salt of an isatic acid in presence of an alkaline earth hydroxide and with the aid of heat. Calcium, magnesium and strontium hydroxides are used in this process which is preferably carried out between room temperature and 100 DEG C. It is also possible to start from an isatin using a correspondingly larger amount of alkaline earth hydroxide to convert this substance to a salt of an isatic acid. In examples: (1) isatin is heated with chloracetone and milk of lime at 80--90 DEG C. to give 2-methyl-3-oxyquinoline-4-carboxylic acid; (2) 5-phenylisatin is heated with milk of lime and then chloracetone added and heating continued at 80--90 DEG C.; 6 - phenyl - 3 - oxy - 2 - methyl - 4-quinoline carboxylic acid is obtained; (3) 5.7-dichlorisatin is similarly treated as in (1) and (2) to give 2-methyl-3-oxy-6.8-dichlorquinoline-4-carboxylic acid; (4) isatin is first treated with caustic soda, slaked lime then added and the mixture reacted with chloracetone at 60--80 DEG C. On heating above the wetting point the products lose carbon dioxide to give the corresponding hydroxyquinaldines On coupling with diazo-compounds they yield azo-dyes also with elimination of carbon dioxide; reduction of these azo-dyes yields the 2-methyl-3-oxy-4-aminoquinolines. The prior art is referred to.