2,2′-Dichlorohydrazobenzene(DHB) was prepared in two steps. o-Chloronitrobenzene( OCNB) was at first reduced to 2,2′-dichloroazoxybenzene(DOB) in aqueous medium using 2,3-dichloro-1,4-naphthaquinone(OCNQ) as catalyst with yield of 99.4%, mp 53～56 ℃; DOB was then reduced by formaldehyde to give DHB in aqueous alkaline methanol with yield of 76%, 49% higher than reported, mp 82～83.5 ℃. DHB could be rearranged to 3,3′-dichlorobenzidine in strong acidic medium with yield 91.8%, mp 132～ 134 ℃.
