Facile synthesis of benzoxazole derivatives by a multi-component reaction catalysed by copper complexes capable of generating phenoxyl radical complex

Abstract

In the present work, mononuclear copper(II) complexes [Cu(L1)Cl](1) and [Cu(L2)Cl](2) having meridional tridentate “NNO” ligands with different substituents have been synthesized and the complexes were characterized by different analytical and spectral techniques, namely FT-IR, NMR, and UV-Vis spectral studies. Molecular structures of complexes 1 and 2 were determined by single-crystal X-ray crystallography. These complexes have been utilized as a catalyst for the synthesis of substituted benzoxazole derivatives under mild conditions. A total of 34 benzoxazole derivatives having different substituents were prepared. The mechanism of this multicomponent reaction, catalysed by complexes 1 and 2, was investigated and the proposed reaction mechanism was based on H-atom abstraction by the phenoxyl radical complex.