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(TM)-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 B-11 NMR and X-ray crystallography.