NCS-Mediated Direct\nC(sp<sup>3</sup>)–H Oxygenation\nof 2‑Methylindoles Using Water as the Oxygen Source

In continuation of our research interest in the green\noxidation\nof indoles, we further explore the direct oxidation of 2-methylindoles\nto 2-formyl indoles promoted by NCS and associated with H<sub>2</sub>O as the oxygen source. This methodology was demonstrated to be a\nrobust protocol consisting of chlorination, S<sub>N</sub>2′,\nand oxidation processes, and presents a reasonably broad substrate\nscope and excellent functional group tolerance, thus enabling the\npreparation of high added-value versatile building blocks susceptible\nto further functionalization.