Phthalic Anhydride → 2-(2-(1H-Benzo[d]imidazol-2-yl)ethyl)isoindoline-1,3-dione

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2-Aminoethylbenzimidazole dihydrochloride (Bull. Soc. Chim. Fr. 1991, 128, 255-259; 2.34 g, 10 mmol), phthalic anhydride (1.63 g, 11 mmol) and triethylamine (2.79 ml, 20 mmol) in chloroform (25 ml) were heated at reflux overnight, and the mixture was then cooled to room temperature, diluted with ethyl acetate and filtered off. The filtrate was washed with saturated sodium carbonate solution, buffer (pH=7) and saturated sodium chloride solution and dried over sodium sulphate. Chromatography (dichloromethane:methanol 10:1, Rf=0.4) gave 2.08 g of 2-(2-phthalimidylethyl)-benzimidazole (71.4% of theory) as a colourless foam. MS (DCI, NH3)=292 (M+H+). 1H-NMR (DMSO-d6): 3.15 (2H, t); 4.0 (2H, t); 7.05-7.2 (2H, m); 7.4-7.5 (2H, m); 7.8-7.9 (4H, m); 12.4 (1H, br s).

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