Unorthodox cascade reaction of arynes and -nitrosamides leading to indazole scaffolds.

An unusual cascade annulation of arynes with -alkyl--nitrosamides is developed by leveraging aryne σ-insertion and C(sp)-H bond functionalization strategies under transition-metal-free conditions at ambient temperature, offering functionalized indazoles in high yields and regioselectivity. The protocol is scalable and exhibits a broad substrate scope. The reaction mechanism is also studied with DFT calculations.