Abstract

MARQUES, Marcelo V.; RUTHNER, Marcelo M.; FONTOURA, Luiz A. M.  and  RUSSOWSKY, Dennis. Metal chloride hydrates as Lewis acid catalysts in multicomponent synthesis of 2,4,5-triarylimidazoles or 2,4,5-triaryloxazoles. J. Braz. Chem. Soc. [online]. 2012, vol.23, n.1, pp. 171-179. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50532012000100024.

A series of nine metal chloride hydrates (ZnCl₂.2H₂O, SnCl₂.2H₂O, CdCl₂.2H₂O, MnCl₂.4H₂O, CoCl₂.6H₂O, SrCl₂.6H₂O, NiCl₂.6H₂O, CrCl₃.6H₂O and CeCl₃.7H₂O) was investigated as mild and inexpensive Lewis acid catalysts to promote the multicomponent synthesis of triarylimidazoles. Reactions starting from benzil showed the best results when SnCl₂.2H₂O was used, while for benzoin as the starting material, CeCl₃.7H₂O was more efficient. All reactions were performed in EtOH as solvent. These catalysts were also successfully employed in the synthesis of triaryloxazoles.

Keywords : triarylimidazoles; triaryloxazoles; multicomponent reaction; metal halide hydrates; Lewis acids; Radziszewski reaction; benzil; benzoin.