An Organozinc Route for the Preparation of Fimctionalized Poly-3-alkylthiophenes

摘要

In 1980, two groups reported the synthesis of unsub-stituted polythiophene utilizing 2,5-dibromothiophene via a Ni-catalyzed method. Since then, several different types of catalysts were employed for the polymerization of 2,5-dibromothiophene. Unfortunately, low molecular weight polymers generally resulted from these attempts. Even though these methods provided interesting materials, there was a big barrier to utilize this polymer due to the lack of process-ability. In order to overcome this difficulty, an alkyl chain was introduced on 3-position of the thiophene ring. Of the many methods, metal-catalyzed cross-coupling polymerization was most frequently used, and the synthesized poly-thiophenes containing an alkyl group equal or greater than C4 are soluble in common organic solvents. This well-established method, however, has significant drawbacks generating inconsistent results and regiorandom polymers. As is known, the regioregularity of the 3-substituted polythiophene plays a critical role in electronic and optical devices. Consequently, developing the efficient methods of preparing highly regioregular head-to-tail poly-3-alkylthio-phenes is of high value. This goal was achieved by two research groups, seperately. Rieke and coworkers reported a synthetic approach to the preparation of regioregular poly-3-alkylthiophene utilizing thienylzinc bromide. The other synthetic method, the McCullough method, was performed by using the Kumada cross-coupling method.