Potassium o-bromobenzoate

A mixture consisting of 22.7 g potassium o-bromobenzoate, 16.6 g 2,6-dichloro-3-methvlani-line, 12 ml N-ethylmorpholine, 60 ml diethylene glycol dimethyl ether, and 1.0 g anhydrous cupric bromide is heated in a nitrogen atmosphere at 145 C to 155°C for 2 hours. The reaction mixture is diluted with 60 ml diethylene glycol dimethyl ether and acidified with 25 ml concentrated hydrochloric acid. The acidic mixture is diluted with 100 ml of water and the liquid phase decanted from the insoluble oil. The insoluble oil is stirred with methanol and the crystalline N-(2,6-dichloro-3-methylphenyl)anthranilic acid which separates is collected and washed with methanol. The product, after recrystallization from acetone-water mixture melts at 248 C to 250°C. 

Diphenic acid has been prepared by the reduction of diazotized anthranilic acid with cuprous ion,6 Ullman coupling of potassium o-bromobenzoate,6 and oxidation of phenanthrene or phen-anthrenequinone with various oxidizing agents.7 The latter methods have been reviewed recently.7 The ozonolysis method has also been carried out in solvents 8 that do not react with the zwitterion intermediate. ... 

Johnson, J. Am. Chem. Soc. 47, 1399 (1925). By heating potassium o-bromobenzoate with copper powder Hurtley, J. Chem. Soc. 1929, 1870,... 

A mixture of 20 g. (0.1 mole) of o-bromobenzoic add, 63 cc. of 10% potassium hydroxide solution, 20 cc. of ethyl alcohol, 40 cc. of 50% tripotassium arsenite solution, and a little freshly reduced copper is refluxed at 90-95° for twelve hours with constant stirring. The reaction mixture is filtered hot to remove copper, made add to Congo red paper with 20 cc. of concentrated hydrochloric add, and evaporated to dryness on a steam cone. The resulting residue is extracted with absolute methanol the methanol extract is evaporated to dryness, and the residue is washed with ether to remove salicylic acid and unchanged o-bromo-... 

The acid has also been obtained by heating o-bromobenzoic acid in 10 per cent, potassium hydroxide with a 50 per cent, aqueous solution of potassium axsenite, 20 c.c. of alcohol and a little copper powder, in a reflux apparatus for ten to twelve hours at about 90° C. 20 grams of o-bromobenzoic acid yield about 12 grams of carboxylated acid. ... 

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