Synthesis of 3‑Chloroindoles via Palladium‐Catalyzed Chlorocyclization of Unmasked 2‑Alkynylanilines

Described herein is the discovery of a palladium‐catalyzed chlorocylization strategy for the synthesis of 3‑chloroindoles tolerated with a wide range of functional groups in moderate to excellent yields. In this transformation, the solvent effect is so important that only THF presents the positive effect. Furthermore, the present method provides an essay access to the N‐unprotected 3‐chloroindoles. A mechanism study showed that 2‐alkynlanilines were catalyzed by palladium to from corresponding indoles, followed by copper‐mediated oxidation chlorination to deliver the 3‐chloroindoles products.