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

摘要

Biaryl compounds 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. Herein, we describepara-selective C-H arylation, which is acheived by a unique combination of ameta-directing group and norbornene as a transient mediator. Upon directmeta-C-H palladation, one-bond relay palladation occurs in presence of norbornene and subsequentlypara-C-H arylation is achieved for sulfonates, phosphonates and phenols bearing 2,6-disubstitution patterns. The protocol is amenable to electron-deficient aryl iodides. Multisubstituted arenes and phenols are obtained by postsynthetic modification of the products. The protocol allows the synthesis of hexa-substituted benzene by sequential selective distal C-H functionalization.