Breaking the Monotony: Cobalt and Maleimide as an Entrant to the Olefin-Mediated Ortho C–H Functionalization

Abstract

A catalytic system is discovered for the intramolecular C–H amidation of N-phenoxy acetamide derivatives. Herein, a cobalt catalyst has been employed for the olefin-mediated ortho C–H functionalization. Moreover, a monocyclic olefin, maleimide, has been used as a transient mediator instead of well-established bicyclic norbornenes. Maleimide promotes a Co­(III) intermediate to undergo oxidative addition into the O–N bond to form a Co­(V) nitrene species and subsequently directs nitrene addition to the ortho position. Mechanistic study and density functional theory (DFT) study support the proposed mechanism. The products derived from this methodology have been demonstrated as a ligand in the C–H olefination reaction. Furthermore, the synthetic utility of this methodology was demonstrated via the ortho-amidation of estrone.

Ortho C–H Bond Activations in an Atmospheric Microwave Plasma Ion Source

“…However, these reactions have the drawbacks of costly catalysts, and poor atomic economy, which do not align with the green chemistry principles. In this scenario, organic chemists have begun to explore cheaper and environmentally friendly catalytic methods to achieve C–H bond activation, such as cobalt catalyst, ,, photochemical oxidation, electrochemical oxidation, photoelectrochemical catalysis, − etc., but the reaction time still tends to be lengthy.…”

Functionalized Cycloolefin Ligand as a Solution to Ortho-Constraint in the Catellani-Type Reaction

“…To distinguish different C–H bonds in organic molecules and achieve site-selective functionalization, directing group and directing template strategies have been proved powerful in transition-metal catalysis. To further improve efficiency, reactions guided by inherent directing groups, transient directing groups, and transient mediators thrived later, enriching the chemical toolbox and facilitating organic synthesis. Among them, the Catellani reaction serves as a representative, which originally achieved intermolecular ortho -alkylation/ ipso termination of iodoarenes by utilizing the Pd/norbornene (NBE) catalysis (Scheme a).…”

Palladium-Catalyzed [3 + 2] Annulation of ortho-Substituted Iodoarenes with Maleimides via a Consecutive Double Heck-type Strategy

“… − Due to their significant biological properties and pharmaceutical importance, some notable strategies have been established for attaining such heterocyclic frameworks; for instance, transition metal-catalyzed annulations effectively accomplish such heterotricyclic systems. − Despite the aforementioned notable strategies, there is still enough scope to develop efficient synthetic methodologies to accomplish such heterocyclic products. Mainly, maleimide and its derivatives are highly affordable and simple starting materials; therefore, in recent years, chemists have employed maleimides as leading coupling partners under induced catalytic transformations. − Especially, maleimide-based transition metal-catalyzed C–H activations to construct polycyclic molecules have been developed. − On the other hand, Pd-catalyzed activation of aryl halides and their eventual Heck couplings with olefins were found as one of the promising tools for constructing polycyclic molecules, − which can be extended to maleimides to get polycyclic compounds. However, unfortunately, under basic Pd(0) catalysis, maleimides are susceptible to hydrolysis of imide bonds because of the reaction’s basic pH, which drastically limits the use of maleimides from usual olefin coupling partners .…”