Patent ID: 7999112

Claim:
A process for the preparation of 3,3′-diaminobenzidine and its analogues having general formula 1 and the said process comprising the steps of: a) haloginising substituted 2-nitroaniline of formula 4 to the corresponding 4-halo-2nitroaniline of formula 3 on treating with halide in acetic acid by known method, b) homocoupling of substituted 4-halo-2-nitroaniline of formula 3 using transition metal complex catalyst preferably selected from palladium sulphonamide complex of formula 6 and bis[chloro N saccharin palladium (II) complex of formula 8 in the presence of an organic base, at a temperature of 75° -125° C., under inert atmosphere, to obtain a corresponding substituted 3,3′-dinitrobenzidine of formula 2, wherein R 1 is hydrogen and R 2 is methyl, methoxy or amino or R 1 and R 2 are both methyl c) reducing the substituted 3,3′-dinitrobenzidine of formula 2 obtained in step (b) with SnCl 2 .HO and neutralizing the acid with alkali hydroxide to obtain the product of formula 1.