Synthesis of Well-Defined Head-to-Tail-Type Oligothiophenes by Regioselective Deprotonation of 3-Substituted Thiophenes and Nickel-Catalyzed Cross-Coupling Reaction

摘要

Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Kno-chel-Hauser base (TMPMgCl • LiCl) and coupling with bromothiophene using a nickel catalyst. Treatment of 3-hexylthiophene with TMPMgCl • LiCl induces metalation at the 5-position selectively. Subsequent addition of 2-bro-mo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthio-phene by repeating the similar protocol. A concise synthesis of MK-1 and MK-2, which are organic dye molecules bearing an oligothiophene moiety that are used in photovoltaic cells, has been achieved.