| 摘要 |
PROBLEM TO BE SOLVED: To provide an alkylation method of 3,4-dihydroxythiophene-2,5- dicarboxylic acid ester or an alkali metal salt or an alkaline earth metal salt thereof, which is easy to carry out and with which corresponding 3,4- dialkoxythiophene-2,5-dicarboxylic acid ester and 3,4-alkylenedioxythiophene-2,5- dicarboxylic acid ester can be obtained in a high yield in a relatively short reaction period. SOLUTION: The alkylation method is characterized by that 3,4- dihydroxythiophene-2,5-dicarboxylic acid ester or an alkali metal salt or an alkaline earth metal salt thereof is alkylated in the presence of an organic onium salt.
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