Yield:-

Reaction Conditions:

with bromine in water;acetic acid

Steps:

1 6-(3,5-dichloro-4-methylphenyl)-3(2H)pyridazinone
3 To a suspension of 9.5 g. of 6-(3,5-dichloro-4-methylphenyl)-4,5-dihydro-3(2H)pyridazinone in acetic acid at 70° C. was added dropwise 7.2 g. of bromine with stirring. After completion of the dropwise addition, the resulting mixture was heated under reflux for 1 hour. After leaving overnight, the so separated crystalline substance was recovered by filtration, washed with cooled ethyl acetate and dried to give the hydrobromide of the desired product having m.p. 258° - 262° C. (dec.) This product was suspended in 50 ml. of water and neutralized with conc. aqueous ammonia. The resulting solid substance was recovered by filtration, washed with water and dried to give 9.4 g. of the desired product as colorless needles of m.p. 254° - 258° C.

References:

Sankyo Company Limited US4052395, 1977, A