1. A process for the preparation of Fluorescein sodium (1) is having purity
greater than 99.5% by HPLC,
5 wherein the process comprising the steps of:
a) reacting resorcinol (4)
with phthalic anhydride (3)
10 in the presence of Lewis acid to obtain Fluorescein (2);
b) optionally purifying Fluorescein (2); and
c) converting Fluorescein (2) obtain Fluorescein sodium (1) in presence
of suitable base.
15 2. The process as claimed in claim 1, wherein the Lewis acid is selected from
Zinc chloride (ZnCl2), boron trifluoride (BF3), tin tetrachloride (SnCl4),
aluminium chloride (AlCl3), and dichloro (methyl)aluminium (MeAlCl2).
13
3. The process as claimed in claim 1, wherein the base is selected from sodium
hydroxide, sodium methoxide, sodium ethoxide and sodium tert-butoxide.
4. The process as claimed in claim 1, wherein the reaction in each step is
carried out in presence of solvent selected from acetone, ethyl acetate,
5 hexane, heptane, benzene, dichloromethane, methanol, ethanol,
isopropanol, butanol, tetrahydrofuran, acetonitrile, dimethylformamide,
toluene, dimethylsulfoxide, methyl tert-butyl ether, xylene,
dichlorobenzene, nitrobenzene, ethylbenzene, water, or mixtures thereof,
preferably xylene, nitrobenzene, benzene, methanol, isopropanol, water or
10 mixtures thereof.
5. The process as claimed in claim 1, wherein Fluorescein sodium (1) obtained
after purification is having resorcinol and phthalic acid are less than 0.5%
(w/w).
6. The process as claimed in claim 1, wherein Fluorescein sodium (1) obtained
15 after purification is having 2-(2,4-dihydroxybenzoyl)benzoic acid is less
than 0.15% (w/w).