Process for preparing pure valsartan
An improved process for the preparation of substantially pure valsartan employing suitable reagents such as chelating agent and reaction conditions.
1. A process for the preparation of Valsartan, comprising
a) reacting a compound of formula II:
with tributyltin azide in a solvent;
b) quenching the reaction with a base;
c) treating the reaction mixture with charcoal and washing with organic solvent;
d) adjusting the pH of the reaction mixture to 6.0-8.0 using an acid and treating with charcoal and filtering;
e) adding a chelating agent to the reaction mixture;
f) adjusting the pH to 3.0-5.0 using an acid;
g) extracting the aqueous layer with an organic solvent;
h) evaporating the solvent to obtain a residue;
i) taking the residue in ethyl acetate and cooling;
j) filtering and drying the precipitates.
2. The process according to claim 1 , wherein the solvent used is xylene, toluene or a mixture thereof.
3. The process according to claim 1 , wherein the base is an alkali metal hydroxide or an alkaline earth metal hydroxide.
4. The process according to claim 3 wherein the base is sodium hydroxide or potassium hydroxide.
5. The process according to claim 1 , wherein the organic solvent is dichloromethane, chloroform or tetrachloromethane.
6. The process according to claim 1 , wherein the acid used is hydrochloric acid.
7. The process according to claim 1 , wherein the chelating agent used is ethylene diamine tetraacetic acid.
8. The process of claim 1 , wherein the Valsartan obtained comprises no more than 5 ppm of a tin-containing compound.