反应详情

A mixture 1b (11.0 g, 60.2 mmol), ethyl 3-aminobenzoate (9.9 g, 6.2 mmol) and triethylamine (8.34 ml, 60.2 mmol) in anhydrous NMP (5 ml) was heated to 130° C. with stirring under a stream of nitrogen for 4 hours. The cooled mixture was poured into ice-water (100 ml). Ethanol (10 ml) was added and the mixture was stirred until crystallization was completed. The precipitate was filtered off, washed with water and dried to yield ethyl (4-acetyl-2-nitrophenyl)aminobenzoate (19.1 g, 97%). This ester was hydrogenated quantitatively in a mixture of ethanol (400 ml) and dichloromethane (100 ml) using Pd (5% on activated carbon) as the catalyst. The resulting diamine was heated to reflux in formic acid (100 ml) for 1 hour. The cooled mixture was poured into ice-water (400 ml) and the precipitate was filtered off, washed with water and dried to yield 5-acetyl-1-(3-ethoxycarbonyl)phenylbenzimidazole (16.4 g, 91%).

1. stirringthe mixture was stirred until crystallization
2. filtrationThe precipitate was filtered off
3. washwashed with water
4. customdried