Hydrochloric Acid → 1-(4-Trifluoromethoxybenzyl)-1,3-dihydrobenzimidazol-2-one

Participants

Reaction Conditions

Reaction Steps

To a solution of benzimidazolinone (4.02 g, 30 mmol) in abs. DMF (20 mL) there were added 4-trifluoromethoxybenzyl bromide (5 g, 19.6 mmol), potassium carbonate (7.0 g, 50.7 mmol), and a catalytic amount of potassium iodide under a blanket of argon. The reaction mixture was heated to 100° C. over a period of 2 h. Following cooling, the reaction mixture was poured into a mixture of ice (200 g) and 2N hydrochloric acid solution in H2O (100 mL). The resulting precipitate was separated with the aid of a frit and then dried. The residue was taken up in EtOAc (150 mL) and the insoluble components separated. The solvent was removed in vacuo, and the residue was recrystallized from a little EtOAc (20 mL), and the dibenzylated product (S) was precipitated. The mother liquor was again concentrated in vacuo, the residue recrystallized from ethanol, and the precipitated solid matter (S) separated by filtration. The filtrate was purified by means of column chromatography (SiO2, cyclohexane/EtOAc 1:4), and there was obtained 1-(4-trifluoromethoxybenzyl)-1,3-dihydrobenzimidazol-2-one (R) (1.60 mg, 26% of theory, mp: 145-148° C.).

Provenance & Evidence