The direct metal-catalyzed C-H bond activations of organic compounds have emerged as a powerful and ideal method for carbon-carbon (C-C) and carbon-heteroatom (C-N, C-O, etc.) bond formation. Identification of efficient catalytic systems coupled with wide substrate scope made it possible to adopt C-H functionalization as the key reaction to access natural products, materials, agrochemicals, and pharmaceuticals in a step and atom economical manner. Nevertheless, reactions in this field are still dominated by precious 4d or 5d transition metals. Extensive use of heavy metals raises several problems such as limited resources and high cost. Therefore, the use of nonprecious and more abundant metal catalysts is being expected to open up a new horizon in this area. The natural earth abundance of 3d-transition metals translates into cost-effective as well as sustainable catalysts. Among all 3d metals, cobalt has emerged as a versatile and efficient catalyst for C–H activation due to its unique reactivity and selectivity. It is worthy to mention that the strong chelating directing groups such as pyridine, pyrimidine, quinoline are well explored in metal-catalyzed C-H activation. However, it has some basic limitations (removal or modification of <i>DG</i>) after the functionalization of inert C-H bonds. In this context, C-H functionalization via weak chelation is gaining significant attention in recent times, due to synthetically useful, modifiable, and naturally occurring functional groups such as aldehydes, ketones and esters have been employed as the weakly coordinating functional groups for the C-H functionalizations. Herein we have described, the most powerful strategy towards sustainable cobalt catalyzed benzenoid C−H activations of indole and indolines using weakly coordinating directing group, which are more significant from the medicinal point of view.

Weak chelation assisted cobalt catalyzed benzenoid C−H bond functionalizations of indoles and indolines

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.