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

2011; American Chemical Society; Volume: 133; Issue: 42 Linguagem: Inglês

10.1021/ja205953g

1943-2984

Shota Tanaka, Shunsuke Tamba, Daiki Tanaka, Atsushi Sugie, Atsunori Mori,

Catalytic Cross-Coupling Reactions

Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Knochel–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-bromo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthiophene 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.