Patent ID: 6790967
Filing Date: 2004-09-14
Classification: C07D

Abstract:
Process for the preparation of âˆ -tocopherol acetate, comprising: in a first stage, a hydrogenation of trimethylbenzoquinone in a solvent chosen from alkyl acetates comprising 2 to 4 carbon atoms in the alkyl chain is carried out with a supported hydrogenation catalyst chosen from palladium and platinum to form trimethylhydroquinone, in a second stage, after filtration to remove the catalyst of the first stage, the trimethylhydroquinone obtained in the first stage is subjected to a condensation reaction with a phytol in a polar solvent of the ester type and in the presence of a Bronsted acid and of a zinc halide, wherein the condensation reaction is carried out in the presence of an amount of water of between 0.7 molar eq. and 2 molar eq. with respect to the number of moles of zinc halide used and in the presence of an amount of zinc halide of greater than 0.3 molar equivalent with respect to the phytol, said condensation reaction resulting in a second stage reaction medium containing &agr;-tocopherol, in a third stage, the zinc halide is extracted from the second stage reaction medium with water to form an aqueous solution containing the zinc halide and an organic phase containing the &agr;-tocopherol, the aqueous solution is then concentrated under warm conditions so as to leave remaining only at most two moles of water per mole of zinc halide before the aqueous solution is recycled to the second stage of the process, in a fourth stage, the organic phase is concentrated to dryness, so as to remove the polar solvent and its possible byproducts from the &agr;-tocopherol, said &agr;-tocopherol then being acetylated neat under warm conditions by forming an acetylation reaction medium comprising, the âˆ -tocopherol, acetic anhydride, and either an inorganic acid chosen from sulphuric acid or phosphoric acid or an alkaline acetate, said acetylation reaction medium containing no solvent.