Gold Catalyzed Photoredox C1-Alkynylation of N-Alkyl-1,2,3,4- tetrahydroisoquinolines by 1-Bromoalkynes with UVA LED Light

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A synthetic method that combines [Au2(m-dppm)2]Cl2 (dppm=bis(diphenylphosphanyl)methane) and UVA LED (LED=light emitting diode) light (365 nm) to catalyze the regioselective C1-alkynylation of N-alkyl-1,2,3,4-tetrahydroisoquinolines (THIQs) with alkynyl bromides is described. The reaction mechanism was delineated to involve a reductive quench pathway to generate the two posited radical species of the nitrogen-containing heterocycle and organic halide. In contrast, radical formation via an oxidative quench pathway was suggested to be operative in analogous control experiments with a 1-iodoalkyne. The usefulness of this carbon-carbon bond forming strategy was also exemplified by its application to the formal synthesis of the opioid analgesic drug methopholine and synthesis of a protoberberine alkaloid derivative.

Original languageEnglish
Pages (from-to)1313-1321
Number of pages9
JournalAdvanced Synthesis and Catalysis
Issue number6
Publication statusPublished - 1 Jan 2019


  • Alkynylation
  • Gold
  • Homogeneous catalysis
  • Photoredox catalysis
  • Synthetic methods

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