Patent ID: 7255741

Claim:
A process for the isolation of crystalline citalopram base of formula (1) from the alkylation reaction mixture of 1-(4′-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (cyanophthalane) of formula (2) with N,N-dimethylaminopropylchloride in a polar aprotic solvent medium in the presence of a strong base, which 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 filtration.