Process for the preparation of carvedilol form-II
The present invention provides a cost-effective, industrially feasible process for the manufacture of crystalline Carvedilol Form-II using novel Carvedilol salts comprising a step of reacting 4-(2,3-epoxy propoxy)carbazole (II) with 2-(2-methoxy phenoxy)ethyl amine (III) followed by acidification with mineral acid in presence of an organic solvent to yield acid addition salts, treatment of the said salts with base(s) in presence of organic solvent(s), water and isolation from the organic solvent(s) followed by crystallization from ethyl acetate.
1. A process for the preparation of crystalline Carvedilol Form-II using novel salts of Carvedilol, comprising the steps of:
reacting 4-(2,3-epoxy propoxy) carbazole with 2-(2-methoxy phenoxy) ethyl amine in the molar ratio of 1:2.0 to 1:2.5 in an organic solvent selected from monochlorobenzene, ethylene glycol dimethyl ether (monoglyme) and mixtures thereof,
adjusting the pH after completion of the reaction with at least one organic acid in the presence of water and at least one organic solvent and isolating the produced novel Carvedilol salts,
treating the Carvedilol salts with at least one base in the presence of water and methylene chloride followed by separation of organic aqueous layers, and
drying the organic layer followed by removal of the at least one organic solvent and crystallization of the residue in ethyl acetate.
2. A process as claimed in claim 1 , wherein the at least one organic acid is selected from oxalic acid and salicylic acid.
3. A process as claimed in claim 1 , wherein the pH is adjusted to 2.0 to about 3.0.
4. A process as claimed in claim 1 , wherein the at least one organic solvent used during pH adjustment is selected from isopropyl acetate, chlorobenzene and mixtures thereof.
5. A process as claimed in claim 1 , wherein the at least one base is selected from alkali, alkaline metal hydroxides, ammonia, and organic bases.
6. A process as claimed in claim 1 wherein the at least one base is aq. ammonia.
7. A process as claimed in claim 1 , wherein the novel Carvedilol salts are carvedilol oxalate and carvedilol salicylate.
8. A process as claimed in claim 3 , wherein the pH is adjusted to 2.5 to about 2.8.
9. A process as claimed in claim 5 wherein the at least one base is aq. ammonia.