Niobic Acid as a Recyclable Heterogeneous Catalyst for the Solvent-Free Synthesis of Substituted Benzimidazoles
Beatriz M. Vieira, Angelita M. Barcellos, Ricardo F. Schumacher, Eder J. Lenardao and Diego da Silva Alves
Affiliation: LASOL - CCQFA - Universidade Federal de Pelotas - UFPel - P.O. Box 354 - 96010-900, Pelotas, RS, Brazil.
Keywords: Aldehydes, atom-economic, benzimidazoles catalysis, condensation, green chemistry, heterogeneous, heterocycles,
heterocycles, niobic acid, niobium, nitrogen compounds, phenylenediamine, solid catalyst.
We describe here a simple method for the synthesis of several substituted benzimidazoles using niobic acid
Nb2O5.5H2O as heterogeneous catalyst and under solvent-free conditions. This new protocol is general and a range of
aromatic and aliphatic aldehydes were condensed with o-phenylenediamine furnishing the corresponding 1,2-disubstituted
benzimidazoles selectively in good yields. The catalyst was reused up four times giving the respective products in good
yields but with a little decreasing in the selectivity.
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