Oxidative C(sp3)–H functionalization of methyl-azaheteroarenes: a facile route to 1,2,4-triazolo[4,3-a]pyridines

We herein describe an oxidative [4 + 1] annulation used to prepare 1,2,4-triazolo[4,3-a]pyridines in the presence of I2–DMSO. This protocol enables synthesis of triazolo[4,3-a]pyridine–quinoline linked diheterocycles via a direct oxidative functionalization of sp3 C–H bonds of 2-methyl-azaheteroarenes. The reaction shows a wide substrate scope and good functional group tolerance.