Chiral Imidazoline Ligands and Their Applications in Metal‐Catalyzed Asymmetric Synthesis^†

Abstract

As a structural analog of oxazoline, imidazoline (4,5‐dihydroimidazole) has received much attention in the rational design of chiral ligands. The additional N‐substituent provides broader space for fine‐tuning of electronic and steric effects, and it offers a good handle for immobilizing onto solid supports. In the past decades, imidazoline ring has emerged as a powerful candidate for the design of chiral nitrogen‐containing ligands, as well as a significant alternative for oxazoline ring. Various chiral imidazoline ligands have been designed and utilized in asymmetric organic reactions. These new catalysts can not only be applied in classical reactions, but also be employed to develop new organic reactions with high enantioselectivities. This review provides an overview of chiral imidazoline ligands. Their applications in asymmetric synthesis are also summarized.

Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides

“…Recently, chiral biimidazoline (BiIm) ligands were shown to be effective in several enantioselective Ni-catalyzed reactions such as a benzylic C–H arylation and hydroarylation of vinylarenes . Although the ligand class has not been applied to asymmetric cross-electrophile coupling, the structural similarity of BiIm and BiOx ligands, coupled with their additional site for derivatization, drew our interest.…”

Regio‐controllable Cobalt‐Catalyzed Sequential Hydrosilylation/Hydroboration of Arylacetylenes

“…Then, sterically less hindered Lf was applied to afford better yield (entry 2). And the yield was further improved by employing electron‐rich imidazoline iminopyridine (IIP) [20] Lg as the ligand (entry 3). Lowering the catalyst loading and increasing the concentration gave 86 % isolated yield of 3 a (entry 4).…”

“…Chemie Forschungsartikel 22630 www.angewandte.de regioisomer,i ndicating the reactivity of hydroboration was interfered by the former hydrosilylation conditions.T hen, sterically less hindered Lf was applied to afford better yield (entry 2). And the yield was further improved by employing electron-rich imidazoline iminopyridine (IIP) [20] Lg as the ligand (entry 3). Lowering the catalyst loading and increasing the concentration gave 86 %i solated yield of 3a (entry 4).…”

Regio‐controllable Cobalt‐Catalyzed Sequential Hydrosilylation/Hydroboration of Arylacetylenes

“…Chemie regioisomer,i ndicating the reactivity of hydroboration was interfered by the former hydrosilylation conditions.T hen, sterically less hindered Lf was applied to afford better yield (entry 2). And the yield was further improved by employing electron-rich imidazoline iminopyridine (IIP) [20] Lg as the ligand (entry 3). Lowering the catalyst loading and increasing the concentration gave 86 %i solated yield of 3a (entry 4).…”