15 ml (24.00 mmol) of 1.6 molar n-butyllithium solution in hexane are added dropwise to a solution, cooled to -70° C., of 7.61 g (20.00 mmol) of 5-bromo-3-fluoro-2-(4-octyloxyphenyl)pyridine in 400 ml of tetrahydrofuran, and the mixture is stirred at -70° C. for 15 minutes. 7.5 g (40.00 mmol) of triisopropyl borate are subsequently added dropwise, the mixture is stirred at -70° C. for 1.5 hours and warmed to room temperature, 500 ml of ammonium chloride solution and 500 ml of ether are added, and the organic phase is separated off and washed twice with aqueous sodium chloride solution, dried over sodium sulfate and evaporated. The resultant 3-fluoro-2-(4-octyloxyphenyl)pyridine-5-boronic acid is refluxed for 2 hours in 100 ml of tetrahydrofuran with 30 ml of 17.5% strength by weight aqueous hydrogen peroxide solution and subsequently cooled to 0° C., and 200 ml of aqueous sodium sulfite solution are added dropwise. The organic phase is separated off, washed twice with aqueous sodium chloride solution, dried over sodium sulfate and evaporated to dryness. Recrystallization from 1,2-dichloroethane gives 5.08 g of 3-fluoro-5-hydroxy-2-(4-octyloxyphenyl)pyridine. ##STR17##
