NOVELTY - Preparing prasugrel hydrochloride, comprises (a) reacting 5,6,7,7a-tetrahydro-thieno(3,2-c)pyridine-2(4H)-one or its salt with 2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone in presence of inorganic base in solvent to produce 5-(2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl)-5,6,7,7a-tetrahydrothieno(3,2-c) pyridin-2(4H)-one (I), (b) acetylating in situ the obtained (I) in step (a), into prasugrel by treating with acetylating agent, and (c) optionally converting the prasugrel of step (b), into prasugrel hydrochloride in the presence of source of hydrogen chloride in organic solvent.    USE - The prasugrel hydrochloride is useful for treating acute coronary syndrome. No biological data given.    ADVANTAGE - The process provides a stable polymorphic form of prasugrel hydrochloride with high purity in a short, industrially scalable, cost-effective and environmental-friendly manner.    DETAILED DESCRIPTION - Preparing prasugrel hydrochloride, comprises (a) reacting 5,6,7,7a-tetrahydro-thieno(3,2-c)pyridine-2(4H)-one or its salt with 2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone in the presence of an inorganic base and in a solvent to produce 5-(2-cyclopropyl-1-(2-fluorophenyl)-2-oxoethyl)-5,6,7,7a-tetrahydrothieno(3,2-c) pyridin-2(4H)-one (I), (b) acetylating in situ the obtained (I) in step (a), into prasugrel by treating with an acetylating agent in the presence of an organic base, and (c) optionally converting the prasugrel of step (b), into prasugrel hydrochloride in the presence of a source of hydrogen chloride in an organic solvent. INDEPENDENT CLAIMS are included for:    (1) preparing prasugrel or its salt, having less than 0.1% of 5-((1RS)-2-cyclopropyl-1-(3-fluorophenyl)-2-oxoethyl)-4,5,6,7-tetrahydrothieno(3,2-c)pyridin-2-yl acetate or any enantiomer of 5-((1RS)-2-cyclopropyl-1-(3-fluorophenyl)-2-oxoethyl)-4,5,6,7-tetrahydrothieno(3,2-c)pyridin-2-yl acetate, comprising (a1) purifying 2-fluoro phenyl acetic acid, so the concentration of 3-fluoro phenyl acetic acid is less than 0.1%, and (b1) preparing the prasugrel or its salt from the 2-fluoro phenyl acetic acid obtained from step (a1);    (2) preparing prasugrel or its salt, having less than 0.1% of the desfluoro impurity, 3-fluoro impurity, 4-fluoro impurity, or any enantiomer of an impurity, comprising (a2) purifying 2-fluoro phenyl acetic acid, so the concentration of 3-fluoro phenyl acetic acid, 4-fluoro phenyl acetic acid, 2-phenyl acetic acid is less than 0.1%, and preparing the prasugrel or its salt involving the use of 2-fluoro phenyl acetic acid obtained from step (a2);    (3) prasugrel or its salt, having less than 0.1% of the methyl impurity and the propionyl impurity;    (4) a process-1 comprising (a3) purifying 2-fluorophenyl acetic acid so that the concentration of 3-fluoro phenyl acetic acid is less than 0.1%, (b3) reacting the pure 2-fluorophenyl acetic acid obtained in step (a3), with ethyl cyclopropanecarboxylate to provide 1-cyclopropyl-2-(2-fluorophenyl)ethanone, and (c3) brominating 1-cyclopropyl-2-(2-fluorophenyl) ethanone obtained in step (b3) with a suitable brominating agent to provide 2-bromo-1-cyclopropyl-2-(2-fluorophenyl) ethanone, having less than 0.1% of 2-bromo-1-cyclopropyl-2-(3-fluorophenyl)ethanone;    (5) a process comprising (a4) reacting 2-fluoro phenyl acetic acid with an amine to produce an ammonium salt, and (b4) converting the ammonium salt obtained in step (a4), into 2-fluoro phenyl acetic acid that contains less than 0.1% of 2-phenyl acetic acid, 2-(3-fluorophenyl)acetic acid or 2-(4-fluorophenyl)acetic acid; and    (6) a composition comprising a excipient and the prasugrel hydrochloride.