Selective Synthesis of N‑Unsubstituted and N‑Arylindoles by the Reaction of Arynes with Azirines

The transition-metal-free and temperature-dependent highly selective reaction of arynes with 2H-azirines allowing the synthesis of either N-unsubstituted or N-arylindoles has been developed. At 60 °C, arynes generated from 2-(trimethylsilyl)­aryl triflates smoothly insert into 2H-azirines to form 2,3-diarylindoles with high selectivity. Interestingly, when the reaction was performed at −10 °C, the selectivity was switched to the formation of 1,2,3-triarylindoles in good yields.