The invention relates to a process for the preparation of cyclopropyl benzyl ketone compounds of formula (II) wherein R1 represents fluorine or chlorine atom or C1-4 alkoxy group, by the reaction of a Grignard reagent, obtained from the reaction of compound of formula (V), wherein X represents chlorine or fluorine atom, with the compound of formula (IV), wherein R2 represents C1-4 alkyl group, having a straight or branched chain. The process can be applied preferably on industrial scale. Compound of formula (II), wherein R represents a fluorine atom in position 2 is an intermediate of the preparation process of prasugrel, which is a platelet inhibitor used in the therapy.