Three copper(II) complexes derived from 2‐methylquinoline and cyclic secondary amines: Synthesis and catalytic application in C—N bond forming reactions

Abstract

Three copper(II) complexes (I-III) bearing N,O-bidentate ligands (L 1 -L 3 ), derived from 2-methylquinoline and cyclic secondary amines (including pyrrolidine, morpholine, and 4-methylpiperidine), were successfully prepared and successively employed in construction of C N bonds via the Chan-Lam coupling of 1H-imidazole derivatives with arylboronic acids. X-ray diffraction analysis demonstrated that the central copper(II) atom of II adopted the distorted tetrahedral geometry, which was four coordinated by one nitrogen atom and one oxygen atom from L 2 as well as two chloride atoms. Catalytic studies indicated that complex II displayed higher activity in Chan-Lam reaction than complex I or III. The present protocol for N,O-coordinated-copper complexcatalyzed C N coupling reaction exhibited some advantages such as wide scope of substrates, good yields, and mild conditions.

Recent advances in Chan–Lam coupling reaction

“…In early 2022, Jia and He constructed a novel series of ligands using cyclic secondary amines and 2-methylquinoline and successfully applied them in Chan–Lam coupling. 38 However, among these novel ligands, morpholine-tethered 2-methylquinoline (Fig. 3) showed the highest activity.…”

Copper Complexes with N,N,N-Tridentate Quinolinyl Anilido-Imine Ligands: Synthesis and Their Catalytic Application in Chan−Lam Reactions

“…In addition to metal salts, well-defined copper complexes were also rapidly developed as catalysts for these reactions. Representative examples can be found in Scheme 1b [14][15][16][17][18][19][20][21]. In 2000, Collman and co-workers used 10 mol% of simple Cu complex [Cu(OH)•TMEDA] 2 Cl 2 (TMEDA = N,N,N ,N -Tetramethylethylenediamine) to produce a variety of N-arylimidazoles with good-to-excellent yields by cross-coupling arylboronic acids with imidazole compounds [14].…”

“…Recently, Emerson's group reported a new tetradentate NHCcopper(II) complex, which showed good catalytic activity in the Chan-Lam coupling of aniline and phenylboronic acid [20]. More recently, Jia et al developed an efficient method for the copper-promoted Chan-Lam coupling of 1H-imidazole derivatives with arylboronic acids using an N, O-bidentate Cu complex (8.0 mol%) as a catalyst [21]. Although considerable progress has been made in this field, there are still limitations, such as long reaction times, high catalyst loading, or the use of a base.…”