反应详情

Added to 8.3 g of 1-ethylpiperidine-2,4-dione were 11 g of methyl orthoformate and 20 ml of acetic anhydride. The resultant mixture was refluxed for 7 hours. After allowing the reaction mixture to cool down, excess methyl orthoformate and acetic anydride were distilled off under reduced pressure. The brown residue was distilled under reduced pressure in a Kugelroll apparatus (0.5 mmHg; bath temperature: 200°-250° C.) to obtain 2.7 g of 1-ethyl-3-methoxymethylenepiperidine-2,4-dione as crystals (yield: 25%). The crystals were recrystallized from a mixed solvent of ethyl acetate and hexane to obtain needles.

1. temperatureto cool down
2. distillationexcess methyl orthoformate and acetic anydride were distilled off under reduced pressure
3. distillationThe brown residue was distilled under reduced pressure in a Kugelroll apparatus (0.5 mmHg; bath temperature: 200°-250° C.)