Process for synthesis of coenzyme Q compounds

A process for synthesizing 2,3-dimethoxy-5-methyl-6-substituted-1,4-benzoquinone having the formula ##STR10## wherein R is ##STR11## in which n is an integer from zero to 9, and A and B are hydrogens or A-B is a direct valence bond between the carbon atoms to which they are attached,

• which comprises
• 1. reacting 2-methyl-4,5,6-trimethoxyphenol with a member selected from the group consisting of borax, boric anhydride, orthoboric acid and metaboric acid to form the corresponding borate,
• 2. reacting the borate obtained in step (1 ) with a prenol compound having the formula ##STR12## an iso-prenol compound having the formula ##STR13## wherein R has the same meaning as defined above, or a corresponding halide derivative thereof, in the presence of a silica-alumina compound, to obtain the 2-methyl-3-substituted-4,5,6-trimethoxyphenyl borate,
• 3. hydrolyzing the borate obtained in step (2) to obtain a compound having the formula ##STR14## wherein R has the same meaning as defined above and then reacting the latter compound with a mild oxidizing agent to obtain a compound of the first-named formula.