Phthalimide → 8-Chloro-5-(1-ethylpropyl)-2,3-dihydro-1H-imidazo[1,2-a]benzimidazole

Participants

Reaction Steps

To a solution of 2-[2,4-Dichloro-7-(1-ethylpropyl)-1H-benzimidazol-1-yl]ethanol (1.41 g, 4.681 mmol) in tetrahydrofuran (18 mL) were added triphenylphosphine (1.84 g, 7.022 mmol), diethylazodicarboxylate (ca. 2.2 mol/L in toluene, 3.19 mL, 7.022 mmol) and phthalimide (1.03 g, 7.022 mmol). The reaction mixture was stirred at room temperature for 2 hrs. The mixture was concentrated in vacuo. The residue was purified by silica gel column chromatography eluting with a 0-30% ethyl acetate/n-hexane gradient mixture to give the mixture containing the title compound. To a solution of the crude material in tetrahydrofuran (12 mL) and ethanol (1 mL) was added hydrazine monohydrate (2 mL). The reaction mixture was stirred at room temperature for 7 hrs. The precipitate was removed by filtration. The filtrate was concentrated in vacuo, and the residue was recrystallized with ethyl acetate/tetrahydrofuran to give the title compound as a colorless solid (725.5 mg, 2.751 mmol, 59%).

Provenance & Evidence