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

An unusual cascade annulation of arynes with N-alkyl-N-nitrosamides is developed by leveraging aryne σ-insertion and C(sp3)-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.