Copper Catalyzed C−H Activation

Abstract

Activation of C−H bonds and their application in cross coupling chemistry has received a wider interest in recent years. The conventional strategy in cross coupling reaction involves the pre‐functionalization step of coupling reactants such as organic halides, pseudo‐halides and organometallic reagents. The C−H activation facilitates a simple and straight forward approach devoid of pre‐functionalization step. This approach also addresses the environmental and economical issues involved in several chemical reactions. In this account, we have reported C−H bond activation of small organic molecules, for example, formamide C−H bond can be activated and coupled with β‐dicarbonyl or 2‐carbonyl substituted phenols under oxidative conditions to yield carbamates using inexpensive copper catalysts. Phenyl carbamates were successfully synthesized in moderate to good yields by cross dehydrogenative coupling (CDC) of phenols with formamides using copper catalysts in presence of a ligand. We have also prepared unsymmetrical urea derivatives by oxidative cross coupling of formamides with amines using copper catalysts. Synthesis of N,N‐dimethyl substituted amides, 5‐substituted‐γ‐lactams and α‐acyloxy ethers was carried out from carboxylic acids using recyclable CuO nanoparticles. Copper nanoparticles afforded N‐aryl‐γ‐amino‐γ‐lactams by oxidative coupling of aromatic amines with 2‐pyrrolidinone. Reusable transition metal HT‐derived oxide catalyst was used for the synthesis of N,N‐dimethyl substituted amides by the oxidative cross‐coupling of carboxylic acids and substituted benzaldehydes. Overview of our work in this area is summarized.

Recent advances in the functionalization of azulene through Rh‐, Ir‐, Ru‐, Au‐, Fe‐, Ni‐, and Cu‐catalyzed reactions

“…Some reviews summarized recent advances in copper-catalyzed C H functionalization. [62,63] For over a century, copper-mediated reactions have played an important role in organic chemistry, as evidenced by numerous important transformations and name reactions. Indeed, Ullmann-type reactions can be thought of as forerunners of modern cross-couplings.…”

Recent Advances in Copper Promoted Inert C(sp3)–H Functionalization

“…Recently, C–H functionalization has become an essential driving force largely accelerating the development of synthetic organic chemistry since it promotes the immediate transformation of omnipresent C–H bonds into C–X (X = C, N, O, S, Cl, Br, etc.) bonds in a single pass, avoiding troublesome functional group manipulations and greatly improving the step economy of reactions . According to the literature, sp 2 and activated sp 3 C–H functionalizations promoted by transition metals have been developed relatively maturely. − However, inert C­(sp 3 )–H functionalization, which in principle should have a propensity to be activated similarly to sp 2 C–H bonds, turns out to be a challenging task and is mainly obstructed by the lack of selectivity and interaction with orbitals of the metal center, thus making C­(sp 3 )–H functionalization still in its early stages …”

PROMETHEUS: A Copper-Based Polymetallic Catalyst for Automotive Applications. Part II: Catalytic Efficiency an Endurance as Compared with Original Catalysts

“…In many cases, the aim of the researchers is to replace palladium or precious metals catalysts with copper catalysts, e.g., copper catalyzed Sonoghasira coupling reaction [ 4 , 5 ]. These efforts are extended to even more sophisticated reactions such C–H activation reactions [ 6 , 7 ]. On the other hand, heterogeneous copper-based catalytic systems demonstrate extremely interesting catalytic properties, especially in oxidation reactions.…”