Patent ID: 7148364

Claim:
A process for the preparation of 1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydro-5-isobenzofuran carbonitrile base, a compound of formula 1, comprising, a) reacting a compound of formula 2, wherein R is Cl or Br, with a cyanide source in presence of an iodide and a suitable solvent selected from the group consisting of amides, amines and polyethers, to obtain the compound of formula 1, b) treating the resultant crude compound of formula 1 obtained in step a) containing, a compound of formula 3, and, a compound of formula 4, with a cyanide reversal agent, wherein the cyanide reversal agent is selected from phosphorous oxyhalides and phosphorous oxides; and isolating the base of compound of formula 1 from the reaction mixture, wherein the compound of formula 1 obtained after isolation has substantially low levels of impurities of formula 3 and formula 4, and optionally converting the compound of formula 1 obtained after isolation, to a pharmaceutically acceptable salt thereof, followed by the conversion of the salt of compound of formula 1 to the base of compound of formula 1, c) further purifying the resultant compound of formula 1 obtained in step ‘b’, from a solvent system, wherein the solvent system comprises a first solvent which is a hydrocarbon solvent and a second solvent, wherein the second solvent is selected from a group consisting of alcohol, ester, ether, ketone or mixture thereof.