Visible-Light-Induced Cascade Difunctionalization of Indoles Enabled by the Synergy of Photoredox and Photoexcited Ketones: Direct Access to Alkylated Pyrrolophenanthridones

  • Org Lett. 2022 Dec 30;24(51):9386-9391. doi: 10.1021/acs.orglett.2c03697.
Su Chen  1 ,  Serena Pillitteri  1 ,  Eduard Fron  2 ,  Luc Van Meervelt  3 ,  Erik V Van der Eycken  1  4 ,  Upendra K Sharma  1
Affiliations
  • 1. Laboratory for Organic and Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
  • 2. Core Facility for Advanced Spectroscopy, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
  • 3. Biomolecular Architecture, Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
  • 4. People's Friendship University of Russia (RUDN University), Miklukho-Maklaya Street 6, RU-117198 Moscow, Russia.
PMID: 36525615 DOI: 10.1021/acs.orglett.2c03697
Abstract

Herein, we describe a methodology to construct polycyclic pyrrolophenanthridones with an (amino)alkyl side chain that involves visible-light-induced decarboxylative radical addition for the intermolecular dearomatization of indoles and subsequent photoinduced C(sp2)-X bond activation via photoexcited ketones for an intramolecular cyclization cascade. Carboxylic acids serve both as a radical source toward indole dearomatization and as reductants to initiate an electron transfer with photoexcited N-acylindole derivatives in the reaction toward pyrrolophenantridone skeletons, which occurs under mild reaction conditions with good functional group tolerance.

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