To an 100 ml tetrahydrofuran solution of 3.5 g of N-tert-butoxycarbonyl-4-piperidone, a 35 ml of 4-phenoxyphenyl magnesium bromide prepared from 4-bromodiphenyl ether (0.6 mol/l tetrahydrofuran solution) was dropwise added under ice cooling and the resultant mixture was stirred for 1 hour. To the reaction mixture was added a 30 ml of saturated aqueous ammonium chloride solution. The product was extracted with ether. The extract was washed with saturated saline, dried, filtered, then concentrated under reduced pressure to give a residue, which was then purified by silica gel column chromatography (hexane:ethyl acetate=3:1) to give N-tert-butoxycarbonyl-4-(4-phenoxyphenyl)-4-piperidinol in an amount of 2.92 g (yield 45%).
