base is selected from sodium hydroxide potassium hydroxide and aqueous ammonia the purified diol thus obtained is treated with optically active acid selected from dibenzoyltartaric acid di p toluoyltartaric acid 10 camphorsulfonic acid and the like in an organic solvent to resolve diol enantiomers to obtain s u2212 4 4 dimethylamino 1 4 fluorophenyl 1 hydroxybutyl 3 hydroxymethyl benzonitrile preferably di p toluoyl d tartaric acid is used to obtain s enantiomer of diol vii having hplc chiral purity of more than 99 5 the s u2212 diol vii is cyclized by using a sulfonyl halide selected from alkylsulfonyl halide such as methanesulfonyl chloride ethanesulfonyl chloride p toluenesulfonyl chloride etc and preferably methanesulfonyl chloride and in presence of a base selected from organic or inorganic base preferably organic base selected from triethylamine diethylamine isopropylamine diisopropylamine n n diisopropylethylamine etc and preferably triethylamine the cyclized product thus obtained is dissolved in an organic solvent selected from acetone acetonitrile ethanol methanol isopropanol tetrahydrofuran toluene cyclohexane isopropyl ether etc and preferably in acetone and is treated with oxalic acid dihydrate to obtain escitalopram oxalate which is isolated and dried by conventional methods this process of the present invention provides escitalopram oxalate with hplc purity more than 99 8 the details of.