Directing group-assisted selective C–H activation of six-membered N-heterocycles and benzo-fused N-heterocycles

Heterocycles are found to be present as the fundamental core compositions of many natural products, agrochemicals, and pharmaceuticals. Among all, the nitrogen-containing heterocycles hold a unique position as a valuable source of therapeutic drugs in medicinal chemistry. Remarkably, the majority of FDA-approved drugs are nitrogen-containing heterocyclic compounds. In this regard, significant progress has been made in this area for the C–H functionalisation of N-heterocycles in the last few decades. Recently, transition metal-catalysed C–H bond activation/functionalisation utilising N-heterocycles as directing group has emerged as a powerful technique. However, the C–H bond activation/functionalisation of N-heterocycles is itself challenging due to the favourable possibility of the metal coordinating to the heteroatom, thus preventing it from activating the desired C–H bond. Therefore, it is essential to emphasise the substantial progress made in this area from a synthetic as well as a medicinal chemistry point of view. Herein, we present the recent advancements made in the directing group-assisted selective C–H bond activation/functionalisation of six-membered N-heterocycles and benzo-fused N-heterocycles, along with some of our thoughts on the future aspects in this area.