Cp*Co(III)‐Catalyzed CH Functionalization Mediated by Oxidizing Directing Groups toward the Synthesis of Heterocycles

Abstract

The utilization of oxidizing directing group for CH activation/functionalization is a unique strategy for the synthesis of a versatile range of heterocycles under redox‐neutral conditions. In this approach, the directing group plays a dual role; controls the product selectivity through its chelation property, and a part of the directing group functions as an internal oxidant. The oxidizing property of the directing groups is due to the oxidizing ability of the NO, NN, NS, NCl bonds. Overall, this synthetic strategy precludes the need for external oxidants, thereby making the process environmentally benign. This article describes significant developments in this area focusing on the Cp*Co(III)‐catalyzed CH functionalization using the oxidizing directing group strategy for the synthesis of heterocycles. The emphasis has been given to the scope and generality of the reactions along with their mechanistic understanding.

Redox-neutral C–H annulation strategies for the synthesis of heterocycles via high-valent Cp*Co(iii) catalysis

“…1). 3 For such reactions, the DG plays a dual role in directing the upcoming group and oxidizing the metal center at the end of the cycle, so they are commonly termed the oxidizing directing group (DG ox ). For this, there are certain atoms/bonds ( e.g.…”

Harnessing Vinyl Acetate as an Acetylene Equivalent in Redox-Neutral Cp*Co(III)-Catalyzed C–H Activation/Annulation for the Synthesis of Isoquinolones and Pyridones

“…These metal oxidants subsequently lead to the generation of metal wastes at the end of the reaction. In order to circumvent the issue of using an external oxidant, redox-neutral C–H annulation reactions involving oxidizing directing groups came into limelight …”

“…In order to circumvent the issue of using an external oxidant, redox-neutral C–H annulation reactions involving oxidizing directing groups came into limelight. 5 …”

Reverse Regioselective Cp*Co(III)-Catalyzed [4 + 2] C–H Annulation of N-Chloroamides with Vinylsilanes: Synthesis of 4-Silylated Isoquinolones and Their Synthetic Utilities

“…In recent years, due to the advent of using of first-row transition metals for C–H functionalizations, Cp*Co­(III) catalysis has provided a viable alternative for expensive catalysts based on precious metals like Pd, Rh, and Ru . It has been widely utilized for the synthesis of isoquinolone scaffolds via [4 + 2] C–H activation/annulation under redox-neutral conditions using oxidizing directing groups such as N -methoxyamides and N -chloroamides. , However, in all these reports, the utilization of the terminal olefins or alkynes often led to the formation of 3-substituted isoquinolone derivatives, and the α-carbon of the olefins/alkynes gets attached to the N -atom of the isoquinolones (Scheme b). For instance, the use of styrene derivatives and allyl silanes led to the formation of 3-substituted isoquinolones exclusively.…”