Synthesis and structure of bifunctional N-alkylbenzimidazole phenylboronate derivatives

N-Methyl and N-n-butyl-2-(2-boronophenyl)benzimidazoles are accessed from the corresponding mono-N-alkyl-ortho-phenylenediamines, either using a polyphosphoric acid-mediated cyclisation with ortho-bromobenzoic acid, or preferably using an Oxone-mediated cyclisation of the corresponding aldehyde, followed by a lithium-exchange and borylation sequence. The resulting boronic acids show unusual physical and chemical properties, as shown by 11B NMR and X-ray crystallography.