Intramolecular [4 + 2] Cycloaddition via Photoredox Dual Dearomatization of Indole and Furan Units

Abstract Despite significant advances in the field of dearomatization, dual dearomatization remains underdeveloped. Herein, we report an intramolecular dual dearomatization reaction of indoles and furans by photoredox catalysis. This method enables the construction of four fused rings in a single step with exceptional regio- and diastereoselectivities under mild conditions. The products can be converted into furan-fused polycyclic scaffolds in a one-pot procedure by using p-toluenesulfonic acid. The synthetic utility of this approach was demonstrated through gram-scale synthesis and several downstream transformations. Mechanistic studies revealed that this reaction proceeds via a single-electron transfer (SET) pathway rather than an energy transfer pathway.