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Synlett 1999; 1999(3): 307-310
DOI: 10.1055/s-1999-2598
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Parallel Synthesis of Polyethylene Glycol Supported Biaryl Benzimidazoles and Imidazopyridines

Carsten G. Blettner* , Wilfried A. König, Gerd Rühter, Wolfgang Stenzel, Theo Schotten
  • *Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany; Fax +49-40-49 09-58 51; E-mail: schotten_theo@lilly.com
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Publication Date:
31 December 1999 (online)

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The parallel synthesis of 25 biaryl 1H-benzimidazoles, 1H-imidazo[4,5-b]pyridines and 1H-imidazo[4,5-c]pyridines on soluble polyethylene glycol support is described. Polymer-esterified biaryl aldehydes were prepared in parallel fashion by coupling polymer-bound aryl halides with o-, m-, or p-formyl benzene boronic acid in a first step. Subsequently the aldehydes were treated with o-arylenediamines to form the title compounds. Nitrobenzene was used as solvent and oxidant in this one-pot conversion. The polymer support remained stable under the drastic conditions (180 °C, 3d) necessary for quantitative conversion as determined by MALDI-TOF-MS. The recovery of the polymer-bound products was good to excellent, but cleavage of the ester bond off the polymeric support (up to 33%) was observed as the main side reaction. Transesterification with sodium methanolate and subsequent purification by solid phase extraction with strongly acidic ion exchange resin and flash chromatography yielded the desired methyl ester.

benzimidazole - suzuki reaction - polyethylene glycol - liquid-phase synthesis