Synthesis and characterization of bisoxazolines- and pybox-copper(ii) complexes and their application in the coupling of α-carbonyls with functionalized amines

Abstract

Binuclear complexes [{(DMOX)CuCl}₂(μ-Cl)₂] (1), mononuclear complexes [(DMOX)CuBr₂] (2) (DMOX = 4,5-dihydro-2-(4,5-dihydro-4,4-dimethyloxazol-2-yl)-4,4-dimethyloxazole) and the pybox Cu(II) complex [(Dm-Pybox)CuBr₂] (3) (Dm-Pybox = 2,6-bis[4′,4′-dimethyloxazolin-2′-yl]pyridine) were obtained by reactions of CuX₂ (X = Cl, Br) with DMOX and Dm-Pybox ligands, respectively. The molecular structures of 1, 2 and 3 have been determined by single-crystal X-ray diffraction analyses. The complexes 2 and 3 are efficient in catalyzing α-amination of ketones and esters through α-bromo carbonyl intermediate. The procedures are environmentally benign methods using molecular oxygen as an oxidant with water as the only byproduct.