Gold(I)-Catalyzed Rearrangement of 3-Silyloxy-1,5-enynes: An Efficient Synthesis of Benzo[b]thiophenes, Dibenzothiophenes, Dibenzofurans, and Indole Derivatives

Authors

  • Prof. Dr. A. Stephen K. Hashmi,

    Corresponding author
    1. Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 711-685-4205
    • Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 711-685-4205
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  • Weibo Yang,

    1. Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 711-685-4205
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  • Dr. Frank Rominger

    1. Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 711-685-4205
    2. Crystallographic investigation
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Abstract

With the IPr ligand (IPr=1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) on gold(I) excellent yields in the benzanellation of 2-substituted thiophenes, benzothiophenes, pyrroles, benzofurans, and indoles were achieved. The 1-siloxybut-3-ynyl side chains, incorporated in the anellation, are easily accessible by the addition of a propargyl metal reagent to a formyl group and silylation of the alcohol. This conveniently allows an anellation at the position of the formyl group under mild conditions. All reactions involve a 2,3-shift of the side chain in the anellation step and thus, provide an easy access to specific substitution patterns. Only in the case of 2-substituted indoles with their highly nucleophilic 3-position a direct hydroarylation without shift is observed. On the other hand, 3-substituted indoles give the same products as 2-substituted indoles. Then, a 3,2-shift in the indole ring system has to be involved.

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