Pd(II)‐Catalyzed Tandem Intramolecular Oxidative Heck Reaction/C−H Arylation Sequence: One‐Pot Synthesis of 3‐Nitro‐2‐Aryl‐Indoles

The present article describes a Pd(II)‐catalyzed cascade methodology that proceeds in a one‐step sequence via intramolecular oxidative Heck‐type C−C coupling and NO₂‐directed selective C‐2 arylation of in‐situ formed 3‐nitroindoles with haloarenes. Importantly, this highly efficient and atom‐economical cascade protocol utilizes the same catalyst system and affords a diverse library of privileged C‐2‐aryl‐nitroindole scaffolds (5 a–5 aa) in a single step with good to excellent yields. Mechanistic investigations, including radical trapping, control, competition experiments and studies on the effects of EDGs and EWGs, strongly suggest the involvement of σ‐bond metathesis or a base accelerated proton abstraction, followed by the formation of a key intermediate i. e., a highly reactive Ar‐Pd−C‐2‐nitroindole complex, which further signifies the vital role of the NO₂ group in leading the efficiency and regioselectivity of the protocol. In addition, this cascade protocol is applicable in the ‘one pot’ synthesis of architecturally complex C‐5 functionalized (−F/‐Cl/‐Me/‐OMe) C‐2‐aryl‐nitroindoles and offers great potential in terms of biological and pharmaceutical fields.