Process for the isolation of high purity crystalline citalopram base

Abstract

A method is provided for the isolation of high purity crystalline citalopram (1-[3-dimethylamino)propyl}-1-(4-fluorophenyl)-1, 3-dihydro-5-isobenzofurancarbonitrile) base directly from the alkylation reaction mixture of 5-cyanophthalane with N,N-dimethylaminoprpylchloride in a polar aprotic solvent using a strong base. The method comprises: (a) diluting the reaction mixture with ice cold water and extracting the resulting mixture with a water-immiscible organic solvent; (b) re-extracting the water-immiscible organic solvent extract with an aqueous acid; (c) diluting the aqueous acid extract with a substantially equal volume of a water miscible organic solvent, based on the volume of water in the aqueous acid extract; (d) adjusting the pH to basic with an inorganic base to precipitate free crystalline base and (e) further isolating the precipitated free crystalline base by filration.

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