300 mg (0.88 mmol) of (2R,4R)-4-(3-chloro-4-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)hexanal and 140 mg (0.88 mmol) of 5-aminoquinolin-2(1H)-one are dissolved in 19 ml of toluene and the solution is admixed with 0.55 ml (1.75 mmol) of titanium tert-butoxide and 0.1 ml of acetic acid. The reaction mixture is heated at 100° C. for 2 hours, cooled, poured into water and stirred vigorously. The suspension is filtered through Celite, the filter bed being rinsed thoroughly with ethyl acetate. The phases of the filtrate are separated and extraction is carried out again with ethyl acetate. The extracts are washed with saturated sodium chloride solution and dried over sodium sulphate and the solvent is removed in vacuo to give 539 mg of (5-{[(2R,4R)-4-(3-chloro-4-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)hexylidene]amino}quinolin-2(1H)-one as a crude product. The imine is dissolved in 44 ml of CH2Cl2 and the solution is cooled to −30° C. 8.9 ml (8.9 mmol) of a 1M BBr3 solution in dichloromethane are added slowly dropwise over 15 minutes and the mixture is allowed to warm to room temperature over 22 hours. The reaction solution is poured onto a mixture of saturated NaHCO3 solution and ice. It is extracted repeatedly with ethyl acetate and the extracts are washed with saturated NaCl solution and dried over Na2SO4. Purification by column chromatography on silica gel (hexane/ethyl acetate 0-100%) yields 134 mg of the title compound.
