Hydrochloric Acid → 5-Carboxy-2,1,3-benzoxadiazol-1-ium-1-olate

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Reaction Conditions

Reaction Steps

In a 3 L reactor fitted with mechanical stirring, reflux condenser, thermometer and nitrogen inlet, KOH (72.46 g) was dissolved in ethanol (250 ml) and water (250 ml). 4-Amino-3-nitrobenzoic acid (100 g) was added and the orange suspension was heated to 65-70° C. within 30 minutes. The resulting suspension was stirred at the same temperature for 45 minutes and cooled to 0° C.±5° C. within 30 minutes. A commercially available (13% w/w) solution of sodium hypochlorite (448.93 g) was added drop wise within 1.5 hours at 0° C.±5° C. The reaction mixture was stirred at the same temperature for 2 hours and controlled by TLC (CHCl3 100/acetone 2/acetic acid 1). Water (350 ml) was added within 15 minutes at 0° C.±5° C. to give a fine yellow suspension. The reaction mixture was then acidified with a 6N HCl solution (239 ml) until 0.5<pH<1 was reached. Sodium chloride (58.44 g) was added and the resulting suspension was stirred at 0° C.±5° C. for 1.5 hours under nitrogen. The solid was collected by filtration, washed with 3×400 ml water and dried (40° C., 30 mbars, 12 hours) to yield 83.6 g (88.8% yield) of [2,1,3]-benzoxadiazole-5-carboxylic acid N-oxide.

Provenance & Evidence