反应详情

Under nitrogen atmosphere, bis(triphenylphosphine)palladium chloride (435 mg, 620 μmol) was added to a toluene (125 ml) solution of 6-bromo-4-cyano-7-fluoro-N,N,5-trimethyl-1,3-benzoxazole-2-carboxamide (I-127) (4.04 g, 12.4 mmol), tributyl(1-ethoxyvinyl)tin (5.37 g, 14.9 mmol) and 2,6-di-tert-butyl-p-cresol (about 20 grains), and heated under reflux for 20 hours. After cooling, the solvent was evaporated away under reduced pressure, then n-hexane was added to the resulting residue and stirred at room temperature for 1 hour. Next, the precipitated solid was collected by filtration and subjected to silica gel column chromatography, and the eluate with n-hexane/ethyl acetate (1:1, v/v) gave 4-cyano-6-[1-(ethoxy)ethenyl]-7-fluoro-N,N,5-trimethyl-1,3-benzoxazole-2-carboxamide (3.20 g, 81%) as a yellow solid. The fraction containing impurities was recovered and purified in the same manner, and 3.57 g (91%) of 4-cyano-6-[1-(ethoxy)ethenyl]-7-fluoro-N,N,5-trimethyl-1,3-benzoxazole-2-carboxamide was obtained in total. The analytical data are shown below.

1. temperatureheated
2. temperatureunder reflux for 20 hours
3. temperatureAfter cooling
4. customthe solvent was evaporated away under reduced pressure
5. additionn-hexane was added to the resulting residue
6. filtrationNext, the precipitated solid was collected by filtration