Transition-Metal-Free Synthesis of Benzimidazoles Mediated by KOH/DMSO
Hannah Baars, Astrid Beyer, Stefanie V. Kohlhepp and Carsten Bolm*
*Institute of Organic Chemistry, RWTH Aachen University,
Landoltweg 1, D-52074 Aachen, Germany, Email: carsten.bolm
oc.rwth-aachen.de
H. Baars, A. Beyer, S. V. Kohlhepp, C. Bolm, Org. Lett., 2014, 16, 536-539.
DOI: 10.1021/ol403414v
Abstract
Intramolecular N-arylations of amidines mediated by potassium hydroxide in DMSO at 120°C enable the preparation of diversely substituted benzimidazoles in good yields.
see article for more examples
Preparation of benzimidazoles:
A solution of the corresponding amidine (0.35 mmol, 1.0 equiv) and KOH (2.0 equiv) in dry DMSO (1.5 mL) was stirred for 14-16 h at 120 °C in a sealed tube. Then, ethyl acetate (2 mL) and water (5 mL) were added to the reaction mixture, the layers were separated and the aqueous layer was extracted with ethyl acetate (3 x 5 mL). The combined organic layers were dried with Na2SO4, the solvent was removed in vacuo and the product was purified by column chromatography.
Key Words
ID: J54-Y2014
