Process for the preparation of pure duloxetine hydrochloride
The present invention relates to a process for the preparation of pure Duloxetine hydrochloride. The present invention further relates to duloxetine hydrochloride substantially free of residual hydrochloric acid.
1. A process for the preparation of pure duloxetine hydrochloride, comprising the steps of
a) treating duloxetine free base with hydrochloric acid in the presence of an organic solvent to obtain duloxetine hydrochloride,
b) isolating the duloxetine hydrochloride from the reaction mixture of step a),
c) washing the isolated duloxetine hydrochloride from step b) with an organic solvent till the pH of the filtrate is in the range of about 5 to about 6, and
d) drying the duloxetine hydrochloride obtained in step c) to obtain pure duloxetine hydrochloride,
wherein the pure duloxetine hydrochloride obtained in step d) has a chloride content of not more than 10.7% w/w.
2. A process according to claim 1 , wherein the hydrochloric acid is used in equimolar quantities with respect to the molar quantity of duloxetine or in slight excess.
3. A process according to claim 1 , wherein the washing is performed by passing the organic solvent through duloxetine hydrochloride, by slurrying the duloxetine hydrochloride in the organic solvent or by a combination thereof.
4. A process according to claim 1 , wherein the pure duloxetine hydrochloride obtained in step d) contains 4-[3-(methylamino)-1-thiophen-2-ylpropyl]naphthalen-1-ol of Formula II of about 0.1% w/w or less