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