Remote ortho-C–H functionalization via medium-sized cyclopalladation

Abstract

Compared to the tremendous progress made in directed ortho-C–H functionalization via five- or six-membered cyclopalladation, protocols with the ability to selectively activate more remote C–H bonds through the intermediacy of larger, less favorable, seven- or eight-membered metalacycles are particularly challenging and remain rare. However, such a strategy would provide new retrosynthetic opportunities for generating structural diversity and complexity. Intense recent research based on the use of either mono-anionic bidentate or monodentate directing groups is characterizing this approach as an increasingly viable tool for selective C–C and C–X bond-forming reactions. This short review provides an overview of these strategies with an emphasis on mechanistic details, synthetic applicability, limitations, and key challenges.