Benzimidazole library group

Activation of amide bonds with an acid (usually at elevated temperatures) to facilitate the 1,2- (or 2,3-) bond formation is a useful method to prepare imidazoles and benzimidazoles (see Section 4.02.9.2(i)). For example, )3-ketoester 1093 possessing a diamino acid (diaminobutanoic acid or ornithine) group is activated by AcOH to form bicyclic imidazole 1094 <2003SL780>. A library of imidazolines, exemplified in Scheme 265, was prepared from Ugi products under acidic conditions <1999TL7925>. 

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