反应详情

温度

60 °C

To a DMF solution of 4-bromo-2-ethylphenol were added potassium carbonate and benzyl bromide, and the whole was stirred at an oil bath temperature of 60° C. for 30 minutes to obtain benzyl (4-bromo-2-ethylphenyl) ether, which was then treated in a similar manner to the first half of Reference Example 2 to obtain methyl 6-(4-benzyloxy-3-ethylphenyl)pyridine-2-carboxylate. The obtained compound was stirred in a mixed solution of methanol and THF in the presence of 10% palladium/carbon under a hydrogen atmosphere of normal pressure at room temperature for 24 hours and then thus obtained product was dissolved in trifluoroacetic acid. Pentamethylbenzene was added thereto under ice cooling and the whole was stirred at an oil bath temperature of 50° C. for 1 hour and further at room temperature for 4.5 days to obtain methyl 6-(3-ethyl-4-hydroxyphenyl)pyridine-2-carboxylate. The obtained compound was treated with trifluoromethanesulfonic anhydride in pyridine to obtain methyl 6-(3-ethyl-4-trifluoromethanesulfonyloxyphenyl)pyridine-2-carboxylate. Further, to a 1,4-dioxane solution of the ester compound obtained above were added tributylvinyltin, lithium chloride, tetrakis(triphenylphosphine)palladium(0), and 2,6-di-t-butyl-4-methylphenol, and the whole was heated to reflux for 18 hours. Thereafter, tetrakis(triphenylphosphine)palladium(0) was further added thereto, followed by 2 days of heating under reflux. Then, potassium fluoride was added thereto at room temperature and the whole was stirred at room temperature for 2 days to obtain methyl 6-(3-ethyl-4-vinylphenyl)pyridine-2-carboxylate. The compound was treated with a 1M aqueous sodium hydroxide solution in methanol to obtain an objective compound.