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Potassium Hydroxide/Dimethyl Sulfoxide Promoted Intramolecular Cyclization for the Synthesis of Benzimidazol-2-ones

Astrid Beyer, Christine M. M. Reucher and Carsten Bolm*

*Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany, Email: carsten.bolmoc.rwth-aachen.de

A. Beyer, C. M. M. Reucher, C. Bolm, Org. Lett., 2011, 13, 2876-2879.

DOI: 10.1021/ol2008878


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Abstract

Intramolecular N-arylations of ureas to form benzimidazol-2-ones occur in the presence of KOH and DMSO at close to ambient temperature. Under these conditions the yields are high and a wide range of functional groups are tolerated.

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General procedure for intramolecular N-arylations:

A sealable tube equipped with a magnetic stir bar was charged with the urea (100 mg, 1.0 equiv) and KOH (2.0 equiv). The aperture of the tube was covered with a rubber septum, and an argon atmosphere was established. Dry DMSO (1.5 mL) was then added by syringe. The septum was replaced by a teflon-coated screw cap, and the reaction mixture was stirred at 40 °C for 24 h. Then, the mixture was cooled to room temperature and water (2 mL) and ethyl acetate (4 mL) were added. The two phases were separated, and the aqueous layer was extracted with ethyl acetate (3 x 3 mL). The combined organic layers were washed with brine (3 mL), dried with anhydrous Na2SO4, filtered and the solvent was removed in vacuo. The product was purified by silica gel column chromatography (n-pentane/ethyl acetate).


Key Words

Benzimidazolones


ID: J54-Y2011-1610