Sustainable Approaches for the site-selective C-H Functionalization of 2H-Indazoles

Heterocyclic moieties are a prominent feature present in natural products, drug molecules and known for their various properties. Especially nitrogen heterocycles are of particular interest in medicinal chemistry, due to their diverse and significant biological properties. Nature has displayed infinite diversity to incorporate these heterocycle scaffolds into a complex structure through evolution. Natural products confine to be the greatest inspiration in drug discovery. The structural complexity and variety of natural products demand developing efficient synthetic methods in green, and sustainable manner was achieved via CH functionalization/activation. Construction of C-C and C-X bonds via C-H bond activation/functionalization has attracted considerable attention in the past decades. However, selective C-H activation has been a challenging task, owing to the ubiquitous nature of the C-H bond in organic molecules. In this aspect, along with transition-metal catalyzed C-H functionalization, recently alternative, metal-free versions have become very important due to economic and environmental concerns. A highly atom economical, efficient and yet environmentally friendly method has been the prime synthetic target to be achieved by the chemists for synthesizing complex heterocycles, since last few decades. Inspired by this, more recent research has been focused on the C-H functionalization of Heteroarenes/arenes, especially radical C-H functionalization become fascinating sustainable method. In this context, we were inspired to take up the challenge of developing novel regioselective C-H functionalization of Heteroarenes to the synthesis of functionalized privileged heterocyclic scaffolds. Accordingly, we have developed a sustainable approach for the site-selective C-H functionalization of 2H-indazoles.