Visible-light-induced intramolecular charge transfer in the radical spirocyclisation of indole-tethered ynones |
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Authors: | Hon Eong Ho Angela Pagano James A Rossi-Ashton James R Donald Ryan G Epton Jonathan C Churchill Michael J James Peter O'Brien Richard J K Taylor William P Unsworth |
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Institution: | Department of Chemistry, University of York, York YO10 5DD UK.; Department of Chemistry and Industrial Chemistry, University of Genova, via Dodecaneso, 31, 16146 Genova Italy |
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Abstract: | Indole-tethered ynones form an intramolecular electron donor–acceptor complex that can undergo visible-light-induced charge transfer to promote thiyl radical generation from thiols. This initiates a novel radical chain sequence, based on dearomatising spirocyclisation with concomitant C–S bond formation. Sulfur-containing spirocycles are formed in high yields using this simple and mild synthetic protocol, in which neither transition metal catalysts nor photocatalysts are required. The proposed mechanism is supported by various mechanistic studies, and the unusual radical initiation mode represents only the second report of the use of an intramolecular electron donor–acceptor complex in synthesis.Indole-tethered ynones form an intramolecular electron donor–acceptor complex that can undergo visible-light-induced charge transfer to promote thiyl radical generation from thiols. |
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