Ultrafast Access to Indole-Fused Isocoumarin with Tunable Emission via Cascade Dual C–H/C–H Cross-Coupling

Employing indole as a synthon in tandem annulation for the construction of polycyclic skeletons remains challenging because of its oxidative dimerization. Herein, we report an ultrafast (5 min) Ir/Cu-catalyzed tandem oxidative [4 + 2] annulation of aromatic acids with indoles, delivering planar indole-fused isochromenes with tunable fluorescence. This transformation involves sequential intermolecular CDC with exclusive C3 selectivity of indoles and intramolecular CDC. Notably, the products can be readily converted to 3-spirooxindole, featuring solvent- and concentration-dependent fluorescence emission properties.