The integration of tandem radical reactions with indole skeletal modification offers an innovative strategy for the efficient construction of nitrogen/oxygen-containing heterocyclic frameworks. Herein we report a novel synthetic approach based on 3-salicyloylindoles. Under visible-light irradiation in an oxygen atmosphere and with the cooperative action of tetrabutylammonium iodide (TBAI), a substrate self-sensitized process enables dual oxidation at C3/C4 of indoles under mild conditions, leading to the efficient assembly of a series of functionalized chromenopyranone derivatives. Notably, this reaction system operates without the need for external photosensitizers or strong oxidants, utilizing only oxygen as the terminal oxidant at room temperature.
Zhu et al. (Tue,) studied this question.