Para-Selective Arylation of Arenes: A Direct Route to Biaryls by Norbornene Relay Palladation.

Biaryls are extremely important structural motifs in natural products, biologically active components and pharmaceuticals. Selective synthesis of biaryls by distinguishing the subtle reactivity difference of distal arene-C-H bonds are significantly challenging. However, prudent orchestration of suitable directing group to mitigate the required geometrical orientation for site selective functionalizations can lead to a handful tool to construct the molecular complexity. Herein we embarked on exploring the para -selective C-H arylation which is contemplated by a unique combination of a meta -directing group and norbornene as transient mediator. Upon direct meta -C-H palladation, one bond relay palladation has been envisioned in presence of norbornene and subsequently para -C-H arylation is achieved for diverse scaffolds with aryl iodides. The scope of the protocol is broad with respect to both the coupling partners.