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Flaky metallic magnesium (2.43 g) was added to 50 ml of dry tetrahydrofuran, and while the mixture was heated, a solution of 20.5 g of 4-bromo-2-fluoroanisole in 100 ml of dry tetrahydrofuran was added dropwise little by little in a stream of nitrogen to prepare a tetrahydrofuran solution of 3-fluoro-4-methoxy-phenyl magnesium bromide. Then, 18.0 g of 4-bromo-2-fluoroanisole was added to 100 ml of dry tetrahydrofuran containing 0.05 g of iodine and 0.1 g of palladium chloride. The mixture was maintained at 40° to 50° C. in a stream of nitrogen, and the above-prepared tetrahydrofuran solution of 3-fluoro-4-methoxyphenyl magnesium bromide was added dropwise gradually. The addition was completely in about 1 hour, and thereafter, the mixture was reacted for 5 hours at the refluxing temperature of tetrahydrofuran. After the reaction, the reaction mixture was after-treated in a customary manner to give 38.2 g of a crude product. The desired product was isolated from the crude product by silica gel column chromatography using ethyl acetate/hexane as an eluent. Thus, 15.0 g of 3,3'-difluoro-4,4'-dimethoxybiphenyl was obtained.

1. temperaturewhile the mixture was heated
2. temperatureThe mixture was maintained at 40° to 50° C. in a stream of nitrogen
3. additionThe addition
4. customAfter the reaction
5. additionthe reaction mixture was after-treated in a customary manner
6. customto give 38.2 g of a crude product