[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[NH:8][NH:9][C:10](=[O:18])[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=1N.N([O-])=O.[Na+]>C(O)C.Cl.O>[F:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[N:8]1[C:16]2[C:11](=[CH:12][CH:13]=[CH:14][CH:15]=2)[C:10]([OH:18])=[N:9]1A stirred suspension of 105 g (0.429 mole) of 2-amino-benzoic acid N′-(2-fluoro-phenyl)-hydrazide in 1250 mL of ethanol and 1250 mL of 1N hydrochloric acid was heated to 55° C. A solution of 59 g (0.858 mole) of sodium nitrite in 200 mL of water was added dropwise over a 30 minute period. Approximately 10 minutes into the addition a solid began separating. External heating was continued until the reaction temperature reached 65° C. and then it was turned off. The temperature remained at 65-68° C. during the addition and gas evolution became vigorous approximately halfway through the addition. Toward the end of the addition, gas evolution slowed and the temperature dropped below 65° C. External heating was reapplied and the mixture was stirred at 70° C. for 3 hours. The mixture was cooled to −10° C. and filtered. The solid was rinsed once with 50 mL of ethanol, then once with 100 mL of water, and pressed dry under suction. Further drying in vacuo at 35° C. for 7 hours afforded 92 g (94%) of product.
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