2025/04/30 by Maximilian Schütze, Matthias Jux, Beatrice Cula +5 · 1 voice
Chemistry · #Oxidative Organic Chemistry Reactions #Metal-Catalyzed Oxygenation Mechanisms #Vanadium and Halogenation Chemistry
paper · pdf · doi:10.1002/asia.202500123
openalex publication_date 2025/04/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/19
Abstract A dinuclear copper(I) complex Cu 2 L2 2 ( L2 = 3,3‐dimethyl‐1‐(1‐methyl‐1 H ‐benzo[ d ]imidazole‐2‐yl)‐ N ‐(propan‐2‐ylidene)butan‐2‐amine) containing benzimidazole and imino donors was previously reported by some of us as an efficient catalyst for the aerobic oxidation of alcohols to aldehydes in presence of TEMPO (2,2,6,6‐tetramethylpiperidinyloxyl) and an external base NMI ( N ‐methyl imidazole). Cu(III) 2 (bis‐ μ ‐oxo) and Cu(II) 2 (bis‐ μ ‐hydroxo) cores were trapped as viable intermediates in the reaction, which provided deeper mechanistic insights. Here, we report two new ligand systems L3 ( N ‐isopropyl‐3,3‐dimethyl‐1‐(1‐methyl‐1 H ‐benzol[ d ]imidazole‐2‐yl)butane‐2‐amine) and L4 (( Z )‐2,4‐di‐ tert ‐butyl‐6‐(((3,3‐dimethyl‐1‐(1‐methyl‐1 H ‐benzol[ d ]imidazole‐2‐yl)butane‐2‐yl)imino)methyl)phenol), which are designed to perturb the overall electronics of the complexes and the resulting effects on their O 2 activation mechanisms. The stronger donation of the secondary amine group stabilizes a mononuclear Cu I L3 core, which nevertheless follows a dinuclear O 2 activation mechanism as in Cu 2 L2 2 . Notably, the Cu I L3 /TEMPO catalyst system performs the aerobic oxidation of alcohols to aldehydes with good yields and turnover numbers, even in the absence of NMI. The dinuclear Cu I 2 L4 2 complex involving a non‐innocent phenolate group, in contrast, exhibits depleted catalytic activity, because of the instability of the Cu(III) 2 (bis‐ μ ‐oxo) core against intramolecular H‐atom abstraction to form an alkoxo bridged dicopper(II) complex.