反应详情

Sodium hydride (60% dispersion in oil) (226 mg) is suspended in N,N-dimethylformamide (10 ml), and to the suspension is added dropwise a solution of 3-(1,3-dithiol-2-ylidene)-2,4-dioxopiperidine (1.0 g) (which is prepared in Example 13) in N,N-dimethylformamide (100 ml) while cooling at 0° to 5° C. The mixture is stirred for 10 minutes at the same temperature, and to the mixture is added dropwise methyl iodide (861 mg), and the mixture is stirred at 0° to 2° C. for 1.5 hour. After distilling off the solvent under reduced pressure, the residue is purified by silica gel column chromatography (solvent, n-hexane:ethyl acetate=1:1), and recrystallized from ethyl acetate-isopropyl ether to give 1-methyl-3-(1,3-dithiol-2-ylidene)-2,4-dioxopiperidine (634 mg, 59.5%) as pale yellow needles. m.p. 148.5°-153° C.

1. temperaturewhile cooling at 0° to 5° C
2. stirringthe mixture is stirred at 0° to 2° C. for 1.5 hour
3. distillationAfter distilling off the solvent under reduced pressure
4. customthe residue is purified by silica gel column chromatography (solvent, n-hexane:ethyl acetate=1:1)
5. customrecrystallized from ethyl acetate-isopropyl ether