Synthesis of bis-3,4-dialkoxythiophenes linked by a m-xylene bridge

Abstract

Two examples of bis 3,4-dialkoxythiophenes linked with a m-xylene bridge were synthesized in yields of 18% and 32% in a six step process. The formation of the m-xylene bridge, key reaction of the synthesis, was carried out through Williamson, Mitsunobu and trans-etherification reactions which were subsequently compared on performance and versatility. The Mitsunobu reaction assisted by sonication was found to be the best strategy. These molecules are among the few examples of unsymmetrically substituted 3,4-dialcoxythiophenes. During the synthesis an 18 member heterocycle, closely related to a crown ether was isolated. The details of the XRD structure of this heterocycle are discussed.