Photocatalytic Synthesis of Polycyclic Indolones.

Tanguy Saget,Burkhard König

doi:10.1002/chem.202001324

Abstract

In this work, a photocatalytic strategy for a rapid and modular access to polycyclic indolones starting from readily available indoles is reported. This strategy relies on the use of redox‐active esters in combination with an iridium‐based photocatalyst under visible‐light irradiation. The generation of alkyl radicals through decarboxylative single electron reductions enables intramolecular homolytic aromatic substitutions with a pending indole moiety to afford pyrrolo‐ and pyridoindolone derivatives under mild conditions. Furthermore, it was demonstrated that these radicals could also be engaged into cascades consisting of an intermolecular Giese‐type addition followed by an intramolecular homolytic aromatic substitution to rapidly assemble valuable azepinoindolones.

Highlights

We report a photocatalytic strategy for a rapid and modular access to polycyclic indolones starting from readily available indoles
We report a catalytic access to diverse polycyclic indolones starting from cheap and readily available indole precursors (Scheme 1)
Such indolone motifs are found in a range of indole alkaloids[4] and are valuable intermediates in the total synthesis of related natural products.[5]

Summary

Introduction

We report a photocatalytic strategy for a rapid and modular access to polycyclic indolones starting from readily available indoles. Such indolone motifs are found in a range of indole alkaloids[4] and are valuable intermediates in the total synthesis of related natural products.[5] We studied the use of NAPs 2 derived from carboxylic acids obtained from the reaction of indoles and commercially available cyclic anhydrides (Scheme 2a).

Results

Conclusion