Nickel‐Catalyzed C‐Heteroatom Cross‐Coupling Reactions under Mild Conditions via Facilitated Reductive Elimination

Abstract

The formation of C‐heteroatom bonds represents an important type of bond‐forming reaction in organic synthesis and often provides a fast and efficient access to privileged structures found in pharmaceuticals, agrochemical and materials. In contrast to conventional Pd‐ or Cu‐catalyzed C‐heteroatom cross‐couplings under high‐temperature conditions, recent advances in homo‐ and heterogeneous Ni‐catalyzed C‐heteroatom formations under mild conditions are particularly attractive from the standpoint of sustainability and practicability. The generation of NiIII and excited NiII intermediates facilitate the reductive elimination step to achieve mild cross‐couplings. This review provides an overview of the state‐of‐the‐art approaches for mild C‐heteroatom bond formations and highlights the developments in photoredox and nickel dual catalysis involving SET and energy transfer processes; photoexcited nickel catalysis; electro and nickel dual catalysis; heterogeneous photoredox and nickel dual catalysis involving graphitic carbon nitride (mpg‐CN), metal organic frameworks (MOFs) or semiconductor quantum dots (QDs); as well as more conventional zinc and nickel dual catalyzed reactions.

Emerging concepts in photocatalytic organic synthesis

“…The resulting Ni(III) complex undergoes facile RE of the desired product, and a final photocatalytic SET event regenerates the Ni(0) catalyst. A range of similar strategies for other alkyl radical precursors ( Milligan et al., 2019 ) and various carbon-heteroatom couplings ( Zhu et al., 2020 ) were developed that all have the potential to have a high impact in the synthesis of active pharmaceutical ingredients (APIs).…”

Metal-Free Photocatalysis: Two-Dimensional Nanomaterial Connection toward Advanced Organic Synthesis

“…The key mechanistic aspects are not yet well understood and require further exploration, but it is likely that the specific steps will differentiate according to the type of reaction and catalytic system. 93 Nevertheless, these examples highlight the immense potential for organic synthesis, possibly encompassing a wide range of reactivity. Future developments will depend on the study and definition of the main features of the catalytic cycle for each class of investigated reactions, such as, for example, the dynamics of the SET steps (whether it is a direct transfer, a second coordination sphere transfer, or a solvent-mediated transfer) and the nature of the metal active site.…”

Carbon dot/TiO2nanocomposites as photocatalysts for metallaphotocatalytic carbon–heteroatom cross-couplings

“…To our delight, CD1/TiO 2 served as an active photocatalyst for a range of metallaphotocatalytic carbon-heteroatom crosscouplings. 34 Moderate to excellent yields were obtained for the coupling of aryl halides with an alcohol, a thiol, a sodium sulfonate, and a sulfonamide using slightly adapted conditions (Fig. 3B).…”

“…[31][32][33] The combination of a photo-and a nickel catalyst (termed metallaphotocatalysis) triggers many important carbonheteroatom and carbon-carbon cross-couplings using light as sustainable energy source. 34 Suitable photocatalysts for these reactions range from ruthenium and iridium polypyridyl com- plexes and organic dyes to heterogeneous semiconductors. 34 Moreover, nickel complexes and photocatalysts were combined in bifunctional heterogeneous materials, such as metalorganic frameworks, 35,36 or organic polymers.…”

“…34 Suitable photocatalysts for these reactions range from ruthenium and iridium polypyridyl com- plexes and organic dyes to heterogeneous semiconductors. 34 Moreover, nickel complexes and photocatalysts were combined in bifunctional heterogeneous materials, such as metalorganic frameworks, 35,36 or organic polymers. 37 Titanium dioxide can be sensitized with organic dyes to serve as a visible light photocatalyst for selective organic transformations.…”