64046-47-5

Treatment of 4,4'-dihaloazoxybenzenes with sulfuric acid afforded 4,4'-dihaloazobenzenes (6) as the major product and 5-halo-2-(p-halophenylazo)phenols, the Wallach rearrangement products as minor products, besides 2-halo-5-(halophenylazo)phenols, 2-halo-4-(p-halophenylazo)phenols, and 4-(p-halophenylazo)phenols as abnormal rearrangement products.The reaction of fluoro compounds gave the azophenols (3a or 5a) in the best yields.However, the ratio of 3a to 5a was found to vary with the concentration of sulfuric acid.Treatment of 4-haloazoxybenzenes with sulfuric acid gave 4-(p-halophenylazo)phenols and 4-haloazobenzenes (13) as major products together with 2-(p-halophenylazo)phenols and 5-halo-2-(phenylazo)phenols as minor products.Yields of reduction products 6 and 13 increased as the halosubstituent became heavier in the following sequence: F -> Cl -> Br -> I.