2,6-Di-tert-butyl-4-methylphenol → 4-cyano-6-[1-(ethoxy)ethenyl]-7-fluoro-N,N,5-trimethyl-1,3-benzoxazole-2-carboxamide

Participants

Reaction Steps

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.

Provenance & Evidence