| 摘要 |
A process for the synthesis of 2,3-dimethoxy-5-methyl-6-substituted-1,4-benzoquinones having the formula: <IMAGE> wherein R is <IMAGE> in which n is an integer of 0 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, CHARACTERIZED BY REACTING 2-METHYL-4,5,6-TRIMETHOXYPHENOL WITH AN ARYL BORONIC ACID, A LOWER ALKYL BORONIC ACID OR AN ACID ANHYDRIDE THEREOF TO OBTAIN A 2-METHYL-4,5,6-TRIMETHOXYPHENOL ESTER OF BORIC ACID, REACTING THE RESULTING ESTER WITH AN N-PRENOL OR ISO-PRENOL HAVING THE FORMULA: <IMAGE> wherein R is as defined above, OR A REACTIVE DERIVATIVE OF SAID N- OR ISO-PRENOL, IN THE PRESENCE OF A SILICA-ALUMINA COMPOUND, TO OBTAIN A 2-METHYL-3-SUBSTITUTED-4,5,6-TRIMETHOXYPHENOL ESTER OF BORIC ACID, AND HYDROLYZING THE THUS-OBTAINED ESTER AND TREATING THE RESULTING 2-METHYL-3-SUBSTITUTED-4,5,6-TRIMETHOXYPHENOL HAVING THE FORMULA: <IMAGE> wherein R is as defined above, WITH AN OXIDIZING AGENT.
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