Differently substituted benzimidazoles have been synthesised in very good yields in solvent-free conditions from o-phenylenediamine and aldehydes in the presence of Yb(OTf)3 as catalyst. The method is applicable to aromatic, unsaturated and aliphatic aldehydes and to substituted o-phenylenediamines without significant differences.
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Curini et al. (2004) studied this question.
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