Synthesis of selected Schiff bases and their copper and silver complexes

Imidoyl phenols 1 are a particular group of Schiff bases, involving a phenol ring in the structure of the molecule, with the phenolic proton forming a hydrogen bond with the iminic nitrogen (Figure 1). This feature provides a particular ease of preparation to this class of compounds with respect to other imines, being an acidic activator of the carbonyl group just present into the molecule. The structure of these molecules makes them interesting ligands to form complexes with transition metals. A serie of imidoyl phenols has been easily prepared with a solventless synthesis and used for the preparation of copper and silver complexes. The Cu(II) complexes were prepared by their reaction with CuCl2·2H2O or CuBr2, while the Cu(I) and Ag(I) complexes were prepared by their reaction with monodentate phosphanes and Cu(CH3CN)4PF6 and AgNO3, respectively. Phosphane co-ligands, such as the lipophilic PPh3 and the hydrophilic PTA, were selected for the synthesis of the new Cu(I) complexes to stabilize copper in +1 oxidation state and confer different solubility properties to the corresponding complexes. All the newly synthesized complexes and the corresponding uncoordinated ligands will be investigated for their cytotoxic activity on a panel of human cancer cell lines by means of both 2D and 3D cell viability studies [2]. In addition, selected Cu(I) and Cu(II) complexes will be studied as new catalysts in the "Ullmann-type" [3] for the coupling of two aryl and heteroaryl halides to yield biaryl products and in Kharasch [4] reactions, for cyclic alkenes allylic oxidation. These moieties are important both from a pharmaceutical point of view and as the core of many active ingredients.