Hydrochloric Acid → 7-(1-Ethylprop-1-en-1-yl)-1-methyl-4-(trifluoromethyl)-1,3-dihydro-2H-benzimidazol-2-one

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Reaction Conditions

Reaction Steps

To an ice-cooled solution of, methyl 3-methyl-2-oxo-7-(trifluoromethyl)-2,3-dihydro-1H-benzimidazole-4-carboxylate (2.80 g, 10.2 mmol) in tetrahydrofuran (30 ml) was added a solution of 3M ethylmagnesium bromide in diethylether (13.6 ml, 40.8 mmol) dropwise and stirred at 45° C. for 16 h. Methanol and water were carefully added to decompose excess reagent. 2N hydrochloric acid was added and extracted with ethyl acetate. The extracts were washed with aqueous saturated sodium bicarbonate and water, dried over magnesium sulfate and concentrated in vacuo. Ethanol (40 ml) and conc. hydrochloric acid (10 ml) were added to the residue and the resulting mixture was heated at 80° C. for 6 h. The reaction mixture was concentrated in vacuo. Aqueous saturated sodium bicarbonate was added to the residue and extracted with ethyl acetate. The extracts were washed with water, dried over magnesium sulfate and concentrated in vacuo. The residue was purified by chromatography on silica gel with a 20% ethyl acetate/n-hexane to give 609 mg (2.14 mmol, 21%, cis/trans=3/1) of the title compound as a white powder.

Provenance & Evidence