Journal of the Brazilian Chemical Society
Print version ISSN 0103-5053
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.