A process for the preparation of 3-(cyclopropylmethoxy)-5,5-dimethyl-4-(4-methylsulfonylphenyl)-furan-2-one comprising the following steps: (a) reacting thioanisole with isobutyryl chloride in the presence of a Lewis acid and an organic solvent, thus obtaining 2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound I) (b) reacting 2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound I) with brominating agent in the same organic solvent of step (a), thus obtaining 2-bromo-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound VI) (c) reacting 2-bromo-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound VI) with an aqueous solution of NaOH or KOH in the same organic solvent of step (a) and in the presence of a phase transfer catalyst, thus obtaining 2-hydroxy-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound II) (d) reacting 2-hydroxy-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound II) with acetoxyacetyl chloride in the presence of the same organic solvent of step (a) and a basic compound, thus obtaining 2-methyl-1-[4-(methylsulfanyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VII); (e) reacting 2-methyl-1-[4-(methylsulfanyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VII) in the same organic solvent of step (a) in the presence of a catalyst and a phase transfer catalyst solution in the same organic solvent with hydrogen peroxide, thus obtaining and separating 2-methyl-1-[4-(methylsulfonyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VIII); (f) reacting a solution of 2-methyl-1-[4-(methylsulfonyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VIII) with 1,8-diazabicyclo[5.4.0]undec-7-ene, thus obtaining 3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2 -one (compound IV) (g) reacting 3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2 -one (compound IV) with cyclopropylmethyl bromide in a suitable organic solvent, thus obtaining 3-(cyclopropylmethoxy)-5,5-dimethyl-4-(4-methylsulfonylphenyl)-furan-2-one (a) reacting thioanisole with isobutyryl chloride in the presence of a Lewis acid and an organic solvent, thus obtaining 2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound I) (b) reacting 2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound I) with brominating agent in the same organic solvent of step (a), thus obtaining 2-bromo-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound VI) (c) reacting 2-bromo-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound VI) with an aqueous solution of NaOH or KOH in the same organic solvent of step (a) and in the presence of a phase transfer catalyst, thus obtaining 2-hydroxy-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound II) (d) reacting 2-hydroxy-2-methyl-1-[4-(methylsulfanyl)phenyl]propan-1-one (compound II) with acetoxyacetyl chloride in the presence of the same organic solvent of step (a) and a basic compound, thus obtaining 2-methyl-1-[4-(methylsulfanyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VII); (e) reacting 2-methyl-1-[4-(methylsulfanyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VII) in the same organic solvent of step (a) in the presence of a catalyst and a phase transfer catalyst solution in the same organic solvent with hydrogen peroxide, thus obtaining and separating 2-methyl-1-[4-(methylsulfonyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VIII); (f) reacting a solution of 2-methyl-1-[4-(methylsulfonyl)phenyl]-1-oxopropan-2-yl (acetyloxy)acetate (compound VIII) with 1,8-diazabicyclo[5.4.0]undec-7-ene, thus obtaining 3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2 -one (compound IV) (g) reacting 3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2 -one (compound IV) with cyclopropylmethyl bromide in a suitable organic solvent, thus obtaining 3-(cyclopropylmethoxy)-5,5-dimethyl-4-(4-methylsulfonylphenyl)-furan-2-one