NOVELTY - Preparing (M1) (3S,4R)-3-hydroxy-1-(4-methoxyphenyl)-4-phenylazetidin-2-one (iii), an intermediate of S-(+)-N,N-dimethyl-a-(2-(naphthalenyloxy)ethyl)benzenemethanamine involves: reacting benzaldehyde with p-anisidine to form N-(4-methoxyphenyl)benzaldimine; reacting the compound (i) with acetoxyacetyl chloride to provide racemic 4-aryl substituted i.e. 1-(p-methoxyphenyl-3-acetoxy-4-phenylazetidin-2-one (ii); converting the compound (ii) into its single enantiomer product via lipase-enzyme catalyzed resolution.    USE - For preparing (3S,4R)-3-hydroxy-1-(4-methoxyphenyl)-4-phenylazetidin-2-one, which is used an intermediate for preparing S-(+)-N,N-dimethyl-a-(2-(naphthalenyloxy)ethyl)benzenemethanamine ((S)-dapoxetine) (claimed) for the treatment of men with premature ejaculation (PE).    ADVANTAGE - The method is easy to commercialize and which yields in good quality as well as quantity of intermediate to prepare (S)-dapoxetine. The synthesis of the (S)-dapoxetine provides fewer steps and much higher overall yield. The method is industrially advantageous, reproducible, robust, eco-friendly, inexpensive amenable to scale up process for the preparation of (s)-dapoxetine and its salt.    DETAILED DESCRIPTION - Preparing (M1) (3S,4R)-3-hydroxy-1-(4-methoxyphenyl)-4-phenylazetidin-2-one (iii), an intermediate of S-(+)-N,N-dimethyl-a-(2-(naphthalenyloxy)ethyl)benzenemethanamine involves: reacting benzaldehyde with p-anisidine to form N-(4-methoxyphenyl)benzaldimine of formula (i); reacting the compound (i) with acetoxyacetyl chloride to provide racemic 4-aryl substituted (i.e. 1-(p-methoxyphenyl-3-acetoxy-4-phenylazetidin-2-one) of formula (ii); converting the compound (ii) into its single enantiomer product via lipase-enzyme catalyzed resolution. An INDEPENDENT CLAIM is included for preparing enantiomerically pure S-(+)-N,N-dimethyl-a-(2-(naphthalenyloxy)ethyl) benzenemethanamine from (3S, 4R)-3-hydroxy-1-(4-methoxyphenyl)-4-phenylazetidin-2-one involving: converting (3S,4R)-3-hydroxy-1-(4-methoxy-phenyl)-4-phenyl-azetidin-2-one (iii) to its xanthate derivative i.e. thiocarbonic acid ((3S,4R)-1-(4-methoxy-phenyl)-2-oxo-4-phenyl-azetidin-3-yl) ester methyl ester (iv); subjecting xanthate derivative (iv) to deoxygenation to furnish (S)-1-(4-methoxy-phenyl)-4-phenyl-azetidin-2-one (v); subjecting lactam's p-methoxy-phenyl group of compound (v) to oxidative removal to obtain (S)-4-phenyl-azetidin-2-one (vi); protecting lactam of compound (vi) as its carbamate derivative with (BOC)2O to form (S)-2-oxo-4-phenyl-azetidine-1-carboxylic acid tert-butyl ester (vii); reducting the compound (vii) by lithium aluminum hydride (LAH) to get ((S)-3-Hydroxy-1-phenyl-propyl)-carbamic acid tert-butyl ester (viii); deprotecting the compound (viii) with trifluoroacetic acid (TFA) to get (S)-3-amino-3-phenyl-propan-1-ol amino-alcohol (ix); demethylating the compound (ix) afforded (S)-3-Dimethylamino-3-phenyl-propan-1-ol (x); obtaining of enantiomerically pure (S)-dapoxetine (i.e. (S)-3-dimethylamino-3-phenyl-propan-1-ol).