NOVELTY - Preparing 2-acetoxy-5-(2-fluoro- alpha -cyclopropyl-carbonyl-benzyl)-4,5,6,7-tetrahydro-4H-thieno(3.2-c)-pyridine (prasugrel) (I) comprises reacting 2-fluoro-benzyl chloride (II) with magnesium, adding the formed cyclopropane-carboxylic acid-dimethyl amide (III) to the Grignard reactant which is (2-fluorobenzyl)magnesium chloride (IV), and converting the obtained 1-cyclopropyl-2-(2-fluoro-phenyl)-ethanone (V) into (I).    USE - The process is useful for preparing 2-acetoxy-5-(2-fluoro- alpha -cyclopropyl-carbonyl-benzyl)-4,5,6,7-tetrahydro-4H-thieno(3.2-c)-pyridine (prasugrel) (I) (claimed) which is useful for treating thrombosis or embolia. No biological data given.    ADVANTAGE - The process: provides (I) in high yield, and environmentally friendly and cost effective manner; avoids the use of diethyl ether; provides (V) with high yield and high selectivity; suppresses the formation of certain by-products by using a mixture of tetrahydrofuran and toluene; and avoids the use of low temperature, inflammable and combustible materials.    DETAILED DESCRIPTION - Preparing 2-acetoxy-5-(2-fluoro- alpha -cyclopropyl-carbonyl-benzyl)-4,5,6,7-tetrahydro-4H-thieno(3.2-c)-pyridine (prasugrel) of formula (I) comprises reacting 2-fluoro-benzyl chloride of formula (II) with magnesium, adding the formed cyclopropane-carboxylic acid-dimethyl amide of formula (III) to the Grignard reactant which is (2-fluorobenzyl)magnesium chloride of formula (IV), and converting the obtained 1-cyclopropyl-2-(2-fluoro-phenyl)-ethanone of formula (V) into (I), where the reaction is carried out in a mixture of toluene and tetrahydrofuran, where the tetrahydrofuran is present at 3-20 vol.%, or methyl-tetrahydrofuran. INDEPENDENT CLAIMS are also included for:    (1) preparing a halogenated ketone derivative of formula (V1a) comprising reacting (II) with magnesium, adding (III) to (IV), and halogenating the formed (V);    (2) preparing (V) by using (II), magnesium and (III) in the presence of a mixture of toluene and tetrahydrofuran;    (3) 1-cyclopropyl-2-(2-fluoro-phenyl)-ethanone (V) prepared by the process, where the 1,2-bis-(2-fluorophenyl)-ethane is present at smaller than 10%, preferably smaller than 2%;    (4) preparing 1,2-bis-(2-fluorophenyl)-ethane comprising reacting (II) with magnesium tetrahydrofuran, reacting the formed Grignard compound with a further 0.9-1.1, in preferably 1 molar amount of (II) at 20-70 degrees C, preferably 60-70 degrees C, working up the reaction mixture, if necessary recrystallizing the product, preferably from methanol or ethanol; and    (5) use of 1,3-bis-(2-fluoro-phenyl)-ethane as analytical standard.