Ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)hept-4-enoate → Ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)heptanoate

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Reaction Steps

698 mg (2.56 mmol) of 1,1′-bi-2-naphthol are admixed with 2.56 ml (1.28 mmol) of a 0.5 M titanium tetraisopropoxide solution in toluene and the red solution is stirred at room temperature for 2 hours. 4.26 g (21.9 mmol) of 2-fluoro-6-(1-methylenbutyl)anisole and 5.7 ml (44 mmol) of ethyl trifluoropyruvate are added and the mixture is heated at 140° C. for 18 hours. After cooling it is immediately purified by column chromatography on silica gel (hexane/ethyl acetate 0-15%) to give 5.82 g of ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)hept-4-enoate. 2.6 g (7.1 mmol) of ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)hept-4-enoate are dissolved in 65 ml of methanol and the solution is admixed with 260 mg of palladium on carbon (10%). The suspension is shaken under a hydrogen atmosphere at atmospheric pressure for 4 hours until the hydrogen uptake is 155 ml. The mixture is filtered through Celite, the filter bed being rinsed thoroughly with ethyl acetate. Removal of the solvent gives 2.6 g of ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)heptanoate. 2.6 g (7.1 mmol) of ethyl 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)-heptanoate in 150 ml of diethyl ether are cooled to −10° C. and over 15 minutes 520 g (14.2 mmol) of solid lithium aluminum hydride are added in portions. The mixture is stirred at −15° C. for 1.5 hours, followed by dropwise addition in succession of ethyl acetate and water and by a further hour of stirring until a readily filterable precipitate is formed. 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. Separation by column chromatography on silica gel (hexane/diisopropyl ether 0-15%) yields 2.1 g of 4-(3-fluoro-2-methoxyphenyl)-2-hydroxy-2-(trifluoromethyl)heptanal as a mixture of the diastereomers.

Provenance & Evidence