This article reviews the development of enantioselective C(sp²)-C(sp³) bond construction via nickel-catalyzed cross-coupling reactions. Over the past decade, nickel has emerged as a promising alternative to palladium in this area, offering unique properties such as facile single-electron transfer to C(sp³) electrophiles and rapid C–C reductive elimination from Ni³+. These characteristics make nickel particularly suitable for reductive cross-coupling (RCC), where two electrophiles are coupled and an exogenous reductant is used to turnover the metal catalyst. Nickel-catalyzed RCCs use readily available and stable electrophiles as starting materials and exhibit good functional group tolerance, making them appealing for applications in the synthesis of complex molecules.
The article discusses the development of enantioselective Ni-catalyzed RCCs, focusing on the use of various C(sp³) electrophiles, including benzylic chlorides, N-hydroxyphthalimide (NHP) esters, and α-chloro esters and nitriles. The selection of specific chiral ligands plays a pivotal role in achieving high cross-selectivity and enantioselectivity. The use of heterogeneous reductants, such as Mn⁰, and soluble organic reductants, such as tetrakis(dimethylamino)ethylene (TDAE), is also highlighted. The use of homogeneous reductants, such as TDAE, is well suited for studying the mechanism of the transformation.
The article also highlights the development of enantioselective dual-Ni/photoredox systems using trifluoroborate (BF₃K) salts as radical precursors. Mechanistic studies of two closely related asymmetric reductive alkenylation reactions developed in the laboratory are discussed, along with the factors influencing electrophile activation and the mode of C(sp³) radical generation. The research aims to provide insights into the intricate mechanisms at play in asymmetric Ni-catalyzed RCCs, with the goal of using the rate of electrophile activation to improve the substrate scope of enantioselective RCCs. The insights gained from this research are expected to provide guidance for the development of new methods in this field.This article reviews the development of enantioselective C(sp²)-C(sp³) bond construction via nickel-catalyzed cross-coupling reactions. Over the past decade, nickel has emerged as a promising alternative to palladium in this area, offering unique properties such as facile single-electron transfer to C(sp³) electrophiles and rapid C–C reductive elimination from Ni³+. These characteristics make nickel particularly suitable for reductive cross-coupling (RCC), where two electrophiles are coupled and an exogenous reductant is used to turnover the metal catalyst. Nickel-catalyzed RCCs use readily available and stable electrophiles as starting materials and exhibit good functional group tolerance, making them appealing for applications in the synthesis of complex molecules.
The article discusses the development of enantioselective Ni-catalyzed RCCs, focusing on the use of various C(sp³) electrophiles, including benzylic chlorides, N-hydroxyphthalimide (NHP) esters, and α-chloro esters and nitriles. The selection of specific chiral ligands plays a pivotal role in achieving high cross-selectivity and enantioselectivity. The use of heterogeneous reductants, such as Mn⁰, and soluble organic reductants, such as tetrakis(dimethylamino)ethylene (TDAE), is also highlighted. The use of homogeneous reductants, such as TDAE, is well suited for studying the mechanism of the transformation.
The article also highlights the development of enantioselective dual-Ni/photoredox systems using trifluoroborate (BF₃K) salts as radical precursors. Mechanistic studies of two closely related asymmetric reductive alkenylation reactions developed in the laboratory are discussed, along with the factors influencing electrophile activation and the mode of C(sp³) radical generation. The research aims to provide insights into the intricate mechanisms at play in asymmetric Ni-catalyzed RCCs, with the goal of using the rate of electrophile activation to improve the substrate scope of enantioselective RCCs. The insights gained from this research are expected to provide guidance for the development of new methods in this field.