反应详情

A mixture of ethyl 1-methoxycarbonyl-3-oxopiperidine-4-carboxylate (9.0 g; 39 mmol), ethylene glycol (100 ml), 4-toluenesulfonic acid (0.7 g), and benzene (500 ml) was refluxed for 6 days using a Dean-Stark water separator. The mixture was washed with aqueous sodium carbonate (300 ml; 1 M), water (300 ml), and saturated aqueous sodium chloride (300 ml). The organic phase was dried (K2CO3) and evaporated in vacuo to give 8.6 of an oil. CC [silica gel (Woelm 0.063-0.1 mm): 350 g; eluents: methylene chloride to which ethyl acetate (20-35%) was added] followed by ball-tube distillation at 40 Pa (oven temperature 170° C.) gave VIIIa (7.0 g; 65%) as a colourless oil. IR (film): 2970 (s), 2900 (s), 1730 (s) cm-1. 1H NMR (CCl4): δ4.05 (q, J 7 Hz) and 3.92 (s) (a total of 6H), 3.60 (s) and 3.7-3.0 (m) (a total of 7H), 2.8-2.5 (1H, t), 2.2-1.6 (2H, m), 1.23 (3H, t, J 7 Hz).

1. temperaturewas refluxed for 6 days
2. washThe mixture was washed with aqueous sodium carbonate (300 ml; 1 M), water (300 ml), and saturated aqueous sodium chloride (300 ml)
3. dry with materialThe organic phase was dried (K2CO3)
4. customevaporated in vacuo
5. customto give 8.6 of an oil
6. customfollowed by ball-tube
7. distillationdistillation at 40 Pa (oven temperature 170° C.)
8. customgave VIIIa (7.0 g; 65%) as a colourless oil