Patent ID: 6740755
Filing Date: 2004-05-25
Classification: C09B

Abstract:
A process for preparing an asymmetrical indocyanine dye of the formula comprising the steps of:a) reacting a first quaternised indolenine or substituted indolenine with a compound of the formula (II) â€ƒor hydrochloride thereof, wherein n is 0 or 1 Ph is phenyl or substituted phenyl X is hydrogen, halogen or alkyl, preferably chlorine, in a solvent selected from the group consisting of acetic acid, acetic anhydride and mixtures thereof in the presence of 0.5 to 50% v/v acetyl chloride referred to the acetic acid/solvant, to obtain an intermediate hemicyanine, and b) further reacting said intermediate hemicyanine with a second quaternised indolenine or substituted indolenine different from said first indolenine.