In a 1 L four-neck flask equipped with a thermometer, a Dimroth condenser, a nitrogen introduction tube and an agitator, 99.7 g (0.365 mol) of the second intermediate (dimethyl 5-bromoisophthalate), 1.1 g (0.00419 mol) of triphenylphosphine, 0.275 g (0.00144 mol) of copper iodide and 41.0 g (0.401 mol) of phenylacethylene were charged and nitrogen was passed into the flask. Then, 375 mL of dehydrated triethylamine and 200 mL of dehydrated pyridine were added therein and the mixture was agitated and dissolved. After passing the nitrogen for one hour, 0.3 g (0.000427 mol) of dichlorobis(triphenyl phosphine)palladium was quickly added and the mixture was heated and refluxed in an oil bath for one hour. Then, triethylamine and pyridine were removed under reduced pressure to obtain a brown viscous solution. The solution was added to 500 mL of water and filtered to separate a solid. The solid was washed with 500 mL of water, 500 mL of 5 mol/L hydrochloric acid and 500 mL of water each two times and dried under reduced pressure at 50° C. Thus, 80.6 g of dimethyl 5-phenylethynylisophthalate was obtained (the yield was 75%).
