NOVELTY - Preparing aprepitant (I) comprises reacting 1-(4-fluorophenyl)-2,2-dihydroxyethanone (II) and (R)-2-(1-phenylethylamino)ethanol (II), salifying and converting configuration of obtained salt, reducing and esterifying obtained isomer to obtain (S)-3-(4-fluorophenyl)-4-((S)-1-phenylethyl)morpholin-2-one of (V), reacting obtained compound with dimethyltitanocene and performing reduction hydrogenation to obtain (2R,3S)-2-((R)-1-(3,5-bis(trifluoromethyl)phenyl)ethoxy)-3-(4-fluorophenyl)morpholine (VIII), and reacting obtained compound with 3-(chloromethyl)-1H-1,2,4-triazol-5(4H)-one.    USE - The method is useful for preparing aprepitant (claimed).    ADVANTAGE - The method: is ingenious and simple; avoids use of expensive raw materials; utilizes reagents which are environmentally-friendly; and is suitable for industrial production.    DETAILED DESCRIPTION - Preparing aprepitant of formula (I) comprises reacting 1-(4-fluorophenyl)-2,2-dihydroxyethanone of formula (II) and (R)-2-(1-phenylethylamino)ethanol of formula (III) in presence of acid to obtain intermediate 3-(4-fluorophenyl)-4-((S)-1-phenylethyl)morpholin-2-one of formula (IV), salifying the intermediate (IV) by using hydrochloric acid, and simultaneously carrying out transformational configuration on the obtained salt to obtain a single isomer i.e. (S)-3-(4-fluorophenyl)-4-((S)-1-phenylethyl)morpholin-2-one of formula (V), reducing(V) into alcohol and then carrying out esterification of alcohol and 3,5-bis(trifluoromethyl)benzoyl chloride to obtain (2R,3S)-3-(4-fluorophenyl)-4-((S)-1-phenylethyl)morpholin-2-yl 3,5-bis(trifluoromethyl)benzoate of formula (VI), reacting (VI) with dimethyl titanocene to obtain (2R,3S)-2-(1-(3,5-bis(trifluoromethyl)phenyl)vinyloxy)-3-(4-fluorophenyl)-4-((S)-1-phenylethyl)morpholine of formula (VII) and carrying out reduction hydrogenation reaction on (VII) in presence of metal catalyst to obtain (2R,3S)-2-((R)-1-(3,5-bis(trifluoromethyl)phenyl)ethoxy)-3-(4-fluorophenyl)morpholine of formula (VIII), and reacting (VIII) with 3-(chloromethyl)-1H-1,2,4-triazol-5(4H)-one to obtain (I).    R = H, methoxy, nitro or halo.