Photocatalytic activation of indole alkanols for intramolecular cyclization toward furoindolines

Abstract

An efficient and practical cerium-induced photocatalytic ligand-to-metal charge transfer (LMCT) method was developed for the activation of indole alkanols (tryptophol), enabling the generation of alkoxy radicals that selectively underwent intramolecular addition to the 2,3-C=C bond of indole, thereby initiating indole dearomatization and leading to intramolecular cyclization into furoindoline. This approach addressed the challenge of building a quaternary carbon center at the C3 position of furoindoline. Furthermore, under the same reaction conditions, adding chromone to tryptophol lead to furoindoline formation followed by indole nitrogen-mediated pyran ring-opening of chromone.