An efficient liquid-phase synthesis of 2-alkylthio-5-carbamoylbenzimidazoles 1 is described. Immobilized o-fluoronitrobenzene 2 undergoes nucleophilic addition of primary amine to afford o-nitroaniline derivatives 3. Subsequent reduction of the aromatic nitro group followed by cyclization gives a PEG-bound benzimidazole-2-thione 5. S-Alkylation of polymer-supported scaffold 5 followed by cleavage gives the resulting library in high yield and high purity.
Yeh, C. M., & Sun, C. M. (1999). Liquid-phase synthesis of 2-(alkylthio) benzimidazoles. Tetrahedron Letters, 40(40), 7247–7250. https://doi.org/10.1002/sim.6493