According to the process of the present invention the 5,6,7,7a-tetrahydro-4H-thieno[3,2-c]pyridine-2-on p-toluenesulfonate (HA=PTSA) of the formula (II) and the 2-bromo-1-cyclopropyl-2-(2-fluorphenyl)-ethanon of the formula (III) are stirred in an organic solvent, (preferably in DMF, THF, toluene, acetonitrile) by adding 1-3 mole equivalent, preferably 2-2.5 mole equivalents of amine, at 20-50° C., preferably 20-30° C., for 1-3, preferably 1-2 hours. The reaction mixture is then divided between water and ethyl acetate and the organic phase is dried and evaporated. The residual product is dissolved in an organic solvent (preferably in DMF, THF, toluene, acetonitrile) without isolating the crystalline 5-[2-cyclopropyl-1-(2-fluorphenyl)-2-oxoethyl]-5,6,7,7a-tetrahydro-4H-thieno[3,2-c]pyridine-2-on of the formula (IV). Then 1-2 equivalent, preferably 1-1.5 equivalent of an amine and 1-3 equivalent, preferably 1-2 equivalent of acetic acid anhydride is added to the reaction mixture and it is further stirred at 20-50° C., preferably 20-30° C., for 1-3 hours, preferably 1-2 hours. The reaction mixture is then divided between water and ethylacetate and the organic phase is dried and evaporated. The remaining product is recrystallized from a suitable organic solvent (acetonitrile, diisopropylether, ethanol), from the mixture of an organic solvent and water or from mixture of suitable organic solvents (toluene-ethyl acetate, hexane-ethyl acetate).
