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

Abstract 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, PdCl 2 {κ 2 − N , S  − 2−(4,5-dihydrothiazol-2-yl)aniline} ( 4 ), Pd{κ 2 − N , N’ −2−(4,5-dihydrothiazol-2-yl)aniline} 2 ( 5 ) and Pd{κ 1 2 − N , N’ −κ 2 2 − N , S  − 2−(4,5-dihydrothiazol-2-yl)aniline} 2 ( 6 ), respectively, in good yields. The neutral mononuclear palladium complexes PdCl 2 {κ 2 − N , N’ −(4,5-dihydro-1H-imidazol-2-yl)aniline} ( 7 ) and Pd{κ 2 − N , N’ −2−(4,5-dihydro-1H-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 ).