PROCESS FOR THE PREPARATION OF 2,5-DIMETHYL-4-HYDROXY-2,3-DIHYDROFURAN-3-ONE AND INTERMEDIATES

摘要

1. A process for the preparation of 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one, wherein (a) hex-3-ene-2,5-diol (V) is epoxidized in a conventional manner in the liquid phase, by means of hydrogen peroxide in the presence of an oxide of a metal of subgroups IV to VIII or of a heteropolyacid of one of the acid-forming elements of group VI of the periodic table of the elements, at a pH of from 3 to 7, preferably from 4 to 6, to give 3,4-epoxy-hexane-2,5-diol (II), (b) the resulting 3,4-epoxy-hexane-2,5-diol is converted at 40 to 280 degrees C in a conventional manner, by means of catalytic amounts of an acid, by cleavage of the epoxide ring and subsequent cyclization, into 2,5-dimethyl-3,4-dihydroxy-tetrahydrofuran (III), (c) the resulting 2,5-dimethyl-3,4-dihydroxy-tetrahydrofuran is dehydrogenated by means of oxygen or an oxygen-containing gas over a silver or copper catalyst, at from 400 to 700 degrees C, to give 2,5-dimethyl-4-hydroxy-tetrahydrofuran-3-one (IV), and (d) the resulting 2,5-dimethyl-4-hydroxy-tetrahydrofuran-3-one is oxidized with bismuth oxide, in concentrated acetic acid solution, to give 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one.