反应详情

Benzofurazan-5-carboxylic acid (2.0 g, 12.2 mmol) was suspended in 10 mL dichloromethane. Carbonyl diimidazole (2.0 g, 12.3 mmol) was added, which caused dissolution with gas evolution. The resulting yellow solution was stirred for 40 minutes at room temperature, following which, piperidine (1.2 g, 14.1 mmol) was added. The solution was stirred overnight and then concentrated onto silica. Product was eluted with hexane/ethyl acetate (2:1) and purified by distillation in a kugelrohr at 155-170° C. and 0.5 mmHg. 1-(Benzofurazan-5-ylcarbonyl)piperidine, 2 (2.78 g, 99%), initially a pale yellow oil, crystallized upon cooling. M.p. 88.5-90.5° C. IR: 2938, 2857, 1630, 1519, 1439, 1266, 1223, 996, 881, 816, and 740 cm-1. 1H NMR (500 MHz): δ 7.90 (1H, d, J=9.7 Hz); 7.84 (1H, s); 7.44 (1H, dd, J=9.4 and 1.4 Hz); 3.74 (2H, br s); 3.39 (2H, br s); 1.72 (4H, br s); and 1.57 ppm (2H, br s).

1. dissolutiondissolution with gas evolution
2. additionwas added
3. stirringThe solution was stirred overnight
4. concentrationconcentrated onto silica
5. washProduct was eluted with hexane/ethyl acetate (2:1)
6. distillationpurified by distillation in a kugelrohr at 155-170° C.
7. custom1-(Benzofurazan-5-ylcarbonyl)piperidine, 2 (2.78 g, 99%), initially a pale yellow oil, crystallized
8. temperatureupon cooling