Nickel-catalyzed C−H bond Alkoxylation of Amides with Alcohols

A Redox Transmetalation Step in Nickel-Catalyzed C-C Coupling Reactions

Ni-catalyzed C-H functionalization reactions are becoming efficient routes to access a variety of functionalized arenes, yet the mechanisms of these catalytic C-C coupling reactions are not well understood. Here, we report the catalytic and stoichiometric arylation reactions of a nickel(II) metallacycle. Treatment of this species with silver(I)-aryl complexes results in facile arylation, consistent with a redox transmetalation step. Additionally, treatment with electrophilic coupling partners generates C-C and C-S bonds. We anticipate that this redox transmetalation step may be relevant to other coupling reactions that employ silver salts as additives.

Transition-metal-catalyzed C-H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

The last decade has witnessed the emergence of innovative synthetic tools for the synthesis of fluorinated molecules. Among these approaches, the transition-metal-catalyzed functionalization of various scaffolds with a panel of fluorinated groups (XR_F, X = S, Se, O) offered straightforward access to high value-added compounds. This review will highlight the main advances made in the field with the transition-metal-catalyzed functionalization of C(sp²) and C(sp³) centers with SCF₃, SeCF₃, or OCH₂CF₃ groups among others, by C-H bond activation. The scope and limitations of these transformations are discussed in this review.

Oxidative C-H/N-H Carbonylation of Benzamide by Nickel Catalysis with CO as the Carbonyl Source

An efficient and direct carbonylation of aminoquinoline benzamides has been developed using abundant and inexpensive Ni(OAc)₂·4H₂O as the catalyst and carbon monoxide as a cost-efficient C1 building block. This process features good functional-group tolerance and can be conducted on gram scale. The directing group can be easily removed under mild conditions.

Pd(II)-Catalyzed Chemoselective Acetoxylation of C(sp2)-H and C(sp3)-H Bonds in Tertiary Amides

Palladium-catalyzed chemoselective C(sp²)-H and C(sp³)-H acetoxylation of synthetically useful tertiary amides is reported under relatively mild reaction conditions. This protocol proceeds through the assistance of a weakly coordinated directing group (C═O) and requires low catalyst (1.0 mol %) loading. Diverse functionalities, such as C(sp²)-Cl, C(sp³)-Cl, -CF₃, -COOEt, and -NO₂ groups, including morpholinyl, piperazinyl, and pyrrolidinyl heterocycles, are compatible under the reaction conditions. Further functionalization of this protocol is demonstrated by hydrolysis to alcohols, alcohol-acids, as well as reduction to tertiary amines. A preliminary kinetic isotope effect study supported the rate-limiting C-H bond activation process.

Advances in Transition-Metal-Catalyzed C–H Bond Oxygenation of Amides

C–O bond formation represents a fundamental chemical transformation in organic synthesis to develop valuably oxygenated (hetero)arenes. Particularly, the direct and regioselective C–H bond oxygenation of privileged amides, using a transition metal catalyst and a mild oxygenating source, is a step-economy and attractive approach. During the last decade, considerable progress has been realized in the direct C–H oxygenation of primary, secondary, and tertiary amides. This Short Review compiles the advances in transition-metal-catalyzed oxygenation of C(sp2)–H and C(sp3)–H bonds on various amides with diverse oxygenation sources. The review is categorized into two different major sections: (i) C(sp2)–H oxygenation and (ii) C(sp3)–H oxygenation. Each section is discussed based on the directing group (monodentate and bidentate) attached to the amide derivatives.

1 Introduction

2 C(sp2)–H Oxygenation

2.1 Monodentate Directed

2.2 Bidentate Directed

3 C(sp3)–H Oxygenation

3.1 Monodentate Directed

3.2 Bidentate Directed

4 Conclusion and Outlook

Copper-Catalyzed Direct C(sp3)-H Alkoxylation to Access Quaternary α-Alkoxylated Amino Acid Derivatives

A copper-catalyzed C(sp³)-H alkoxylation was developed to prepare quaternary α-alkoxylated amino acid derivatives in good yields. This protocol can be applied to a series of α-amino acids bearing a variety of functional group substituents. Facile removal of the auxiliary directing group and tolerance of condensation conditions for amide bond formation enable the potential application of this method in the discovery of new peptide drugs in the future.

Bidentate Directing Groups: An Efficient Tool in C-H Bond Functionalization Chemistry for the Expedient Construction of C-C Bonds

During the past decades, synthetic organic chemistry discovered that directing group assisted C-H activation is a key tool for the expedient and siteselective construction of C-C bonds. Among the various directing group strategies, bidentate directing groups are now recognized as one of the most efficient devices for the selective functionalization of certain positions due to fact that its metal center permits fine, tunable, and reversible coordination. The family of bidentate directing groups permit various types of assistance to be achieved, such as N,N-dentate, N,O-dentate, and N,S-dentate auxiliaries, which are categorized based on the coordination site. In this review, we broadly discuss various C-H bond functionalization reactions for the formation of C-C bonds with the aid of bidentate directing groups.

Nickel-catalyzed dual C(sp2)–H activation of arenes: a new route to diaryl ethers

Diaryl ethers are synthesized directly from simple arenes for the first time through dual C(sp²)–H activation with the aid of a bidentate auxiliary by nickel catalysis. The auxiliary can be removed smoothly under mild reaction conditions.

Silver-Mediated Methoxylation of Aryl C(sp2)–H Bonds Directing by DMEDA

The first example of silver-mediated phosphine-promoted methoxylation of aryl C(sp2)–H bonds with the commercially available reagent for the preparation of alkyl aryl ethers has been developed. This protocol is characterized by mild reaction conditions, broad substrate scope, and high regioselectivity.