Patents

The invention provides a reusable transition metal complex catalyet useful for the preparation of high pure quality 3,3'-diaminobenzidine and its analogues. The invention also provides to a process for the preparation of a reusable transition metal complex catalyst. The invention further provides a process for the preparation of 3, 3'-diaminobenzidine (DAB) or 3,3',4,4'-or Tetraminobiphenyl (TAB) using reusable transition metal complex catalyst. The high quality 3, 3'-diaminobenzedine (DAB) and its analogues is prepared by coupling 4-halo-2-nitroaniline to 3, 3'-dinitrobenzidine (DNB) using transition metals as catalysts followed by reduction of 3, 3'-dinitrobenzidine to the corresponding substituted 3, 3'-diaminobenzidine of formula 1 in high yields.