Synthesis and palladium(II) metal chemistry of thiazoline/imidazoline derived ligands: An efficient catalyst for cross-coupling reactions of arylboronic acids with acid chlorides and aryl halides

摘要

The synthesis, reactivity, spectroscopic characterization and catalytic activities of a series of Pd(II) complexes bearing the chelating ligands 2-(4,5-dihydrothiazol-2-yl)aniline (2) and 2-(4,5-dihydro-1H-imidazol-2-yl)aniline (3) are reported. The reactions of 2 with [Pd(COD)Cl-2] in 1:1 and 1:2 (ligand into metal and metal into ligand) molar ratios afforded the mononuclear complexes, PdCl2{kappa(2) - N,S - 2 - (4,5-dihydrothiazol-2-yl)aniline} (4), Pd {kappa(2)- N,N'- 2 - (4,5- dihydrothiazol-2-yl) aniline}(2) (5) and Pd {kappa(2)(1) - N,N'- kappa(2)(2) -N,S - 2 - (4,5- dihydrothiazol-2yl) aniline}(2) (6), respectively, in good yields. The neutral mononuclear palladium complexes PdCl2{kappa(2) - N,N'- (4,5-dihydro-1 H- imidazol-2-yl) aniline} (7) and Pd{kappa(2) - N,N'- 2 - (4,5-dihydro -1 H- imidazol-2-yl) aniline}(2) (8) were synthesized using [Pd(COD)Cl-2] with appropriate molar ratios. The palladium complexes 4-8 were evaluated for their catalytic activities in base assisted cross coupling reactions between acid chlorides and aryl halide with boronic acids. The complex 4 was found to be an efficient catalyst for producing unsymmetrical ketones (TOF = 19.8 min(-1)) while complex 7 was effective for making biaryls (TOF = 19.8 min(-1)).