Nickel-Catalyzed Reductive Cross-Couplings: New Opportunities for Carbon–Carbon Bond Formations through Photochemistry and Electrochemistry

Abstract

Metal-catalyzed cross-electrophile couplings have become a valuable tool for carbon-carbon bond formation. This minireview provides a comprehensive overview of the recent developments in the topical field of cross-electrophile couplings, provides explanations of the current state-of-the-art, and highlights new opportunities arising in the emerging fields of photoredox catalysis and electrochemistry.

C(sp2)–C(sp2) Reductive Cross-Coupling of Triarylphosphines with Aryl Halides by Palladium/Nickel Co-catalysis

“…Transition metal-catalyzed C­(sp 2 )–C­(sp 2 ) reductive cross-coupling reactions of two aryl electrophiles have received a great deal of attention as some of the most efficient methods for the synthesis of biaryls due to the wide availability of electrophiles and because the reactions circumvent the tedious preparation of organometallic reagents . To date, various aryl halides and O-based aryl electrophiles have been utilized in such transformations.…”

Nickel-Catalyzed Regioselective Reductive Ring Opening of Aryl Cyclopropyl Ketones with Alkyl Bromides

“…As a continuation of our ongoing interest in developing new reductive cross-coupling reactions, we turned our attention to utilizing easily accessible electrophilic alkyl halides as the coupling partner with aryl cyclopropyl ketones. Under reductive nickel catalysis, this alkylative ring opening reaction features complete regiocontrol on C–C bond cleavage, efficient Csp 3 –Csp 3 bond formation, as well as the merits of high step-economy and functionality tolerance (Scheme C).…”

DABCO-promoted photocatalytic C–H functionalization of aldehydes

“…In this context, our work aims to broaden the scope of DABCOpromoted photocatalytic C-H functionalization including formyl bonds of aldehydes as substrates (Figure 2e). The acyl radicals generated through this step were used in a well-stablished nickel-catalyzed cross-coupling reaction [19,[27][28][29][30] with aryl bromides as a proof of concept, leading to the synthesis of aryl ketones. We also present computational calculations of the HAT reaction step with the DABCO radical cation as the hydrogen abstractor and isovaleraldehyde as the substrate.…”