An improved process for the preparation of indocyanine green

摘要

The present invention involves an improved process for the preparation of Indocyanine green of Formula (I) having high purity of about 99%, wherein the process comprises steps of reacting 1,1,2-trimethyl-1H-benzo[e]indole with 1,4-butane sulfone in boiling solvent to give 4-(1,1,2-trimethyl-1H-benzo[e]indolium-3-yl)butane-1-sulfonate. Followed by reacting 4-(1,1,2-trimethyl-1H-benzo[e]indolium-3-yl)butane-1-sulfonate of Formula (IV) and N-phenyl-N-((1E,3E,5E)-5-(phenylimino)penta-1,3-dienyl)acetamide of formula (V) in presence of sodium acetate and alcohol; and extracting the title compound formula (I) with an ester solvent.