Catalytic Electrophilic Halogenation of Silyl-Protected and Terminal Alkynes: Trapping Gold(I) Acetylides vs. a Brønsted Acid-Promoted Reaction

Authors

  • Pavel Starkov,

    1. Department of Chemistry, University College London, Christopher Ingold Laboratories, London WC1H 0AJ, U.K. Fax: +(44)-(0)20-7679-7463; phone: +(44)-(0)20-7679-2467
    2. Present Address: Department of Organic Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
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  • Filippo Rota,

    1. Department of Chemistry, University College London, Christopher Ingold Laboratories, London WC1H 0AJ, U.K. Fax: +(44)-(0)20-7679-7463; phone: +(44)-(0)20-7679-2467
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  • Jarryl M. D'Oyley,

    1. Department of Chemistry, University College London, Christopher Ingold Laboratories, London WC1H 0AJ, U.K. Fax: +(44)-(0)20-7679-7463; phone: +(44)-(0)20-7679-2467
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  • Tom D. Sheppard

    Corresponding author
    1. Department of Chemistry, University College London, Christopher Ingold Laboratories, London WC1H 0AJ, U.K. Fax: +(44)-(0)20-7679-7463; phone: +(44)-(0)20-7679-2467
    • Department of Chemistry, University College London, Christopher Ingold Laboratories, London WC1H 0AJ, U.K. Fax: +(44)-(0)20-7679-7463; phone: +(44)-(0)20-7679-2467
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Abstract

In the presence of a cationic gold(I) catalyst and N-halosuccinimide, both trimethylsilyl-protected and terminal alkynes are converted into alkynyl halides. Further experiments showed that silyl-protected alkynes undergo electrophilic iodination and bromination under Brønsted acid catalysis, whilst terminal alkynes require a cationic gold catalyst. The former reactions probably proceed via activation of the electrophile, whilst the latter reactions proceed via a gold(I) acetylide intermediate. Gold-catalysed halogenation was further combined with gold-catalysed hydration and subsequent annulation to provide convenient routes to iodomethyl ketones and five-membered aromatic heterocycles.

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