Copper-Carbene-Triggered Electrophilic Cyclization of o‑Hydroxyarylenaminones with 3‑Diazoindolin-2-imines: Synthesis of 3‑Indolyl‑4H‑chromen-4-ones and Pyrido[2,3‑b:6,5‑b′]diindoles

The Cu­(II)-catalyzed electrophilic cyclization reaction between o-hydroxyarylenaminones and 3-diazoindolin-2-imines furnished 3-indolyl-4H-chromen-4-ones in moderate to good yields with a broad substrate scope. Several pyrido­[2,3-b:6,5-b′]­diindoles and one pyrazino­[2,3-b:5,6-b′]­diindole were also obtained as byproducts in some cases and tested for their photophysical properties. Pyrido­[2,3-b:6,5-b′]­diindoles exhibited solvent-dependent emission, while pyrazino­[2,3-b:5,6-b′]­diindole emitted strong luminescence with 25.6% quantum yield in cyclohexane.