Concise Synthesis of Well-Defined Linear and Branched Oligothiophenes with Nickel-Catalyzed Regiocontrolled Cross-Coupling of 3-Substituted Thiophenes by Catalytically Generated Magnesium Amide

Authors

  • Shota Tanaka,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Daiki Tanaka,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Go Tatsuta,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Kohei Murakami,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Shunsuke Tamba,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Dr. Atsushi Sugie,

    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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  • Prof. Dr. Atsunori Mori

    Corresponding author
    1. Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
    • Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan), Fax: (+81) 78-803-6181
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Abstract

The synthesis of linear and branched oligothiophenes of well-defined structures is performed with regioselective deprotonation of 3-substituted thiophenes and nickel-catalyzed cross-coupling of the thus formed metalated species with a bromothiophene. The reaction of 3-hexylthiophene with EtMgCl and 2,2,6,6-tetramethylpiperidine (TMP-H, 10 mol %) induces the metalation selectively at the 5-position by use of the catalytically generated hindered magnesium amide (TMPMgCl) and the subsequent reaction of a 2-halo-3-hexylthiophene (bromide or chloride) in the presence of a nickel catalyst affords a head-to-tail (HT)-type dimer. By repeating the same sequence, the linear oligothiophene up to a 4-mer is synthesized in good yield. The reaction of 3-hexylthiophene with 2,3-dibromothiophene also takes place to afford a branched oligothiophene 3-mer in quantitative yield. The obtained 3-mer is also metalated at the sterically less-hindered position in a regioselective manner furnishing a 7-mer in >99 % yield after a further coupling reaction with 2,3-dibromothiophene. These dendrimers react with several multifunctionalized organic electrophiles, leading to a variety of branched oligothiophenes.

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