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Synthesis 1992; 1992(4): 395-398
DOI: 10.1055/s-1992-26121
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An Advantageous Synthesis of 2-Substituted Benzimidazoles Using Polyphosphoric Acid. 2-(Pyridyl)-1H-benzimidazoles, 1-Alkyl-(1H-benzimidazol-2-yl)pyridinium Salts, their Homologues and Vinylogues

Ermitas Alcalde* , Immaculada Dinarés, Lluïsa Pérez-García, Tomàs Roca
  • *Laboratorio de Química Orgánica, Facultad de Farmacia, Universidad de Barcelona, E-08028-Barcelona, Spain
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Publikationsdatum:
17. September 2002 (online)

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The title 2-substituted benzimidazoles are prepared by a highly efficient one-pot procedure, cyclodehydration of the corresponding accessible carboxylic acids and 1,2-arylenediamines, using polyphosphoric acid as the catalyst and solvent in a condensation of the type found in the Phillips benzimidazole synthesis. The method has been adapted and proved to be extremely useful for 1-alkyl-(1H-benzimidazol-2-yl) pyridinium tetrafluoroborates with a methylene and vinylene interannular moiety.