Hydrochloric Acid → 2-Chloro-3-fluoro-6-(1-methylenepropyl)anisole

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反応手順

21.5 g (146.7 mmol) of 2-chloro-3-fluorophenol (R. Sanz et al. J. Org. Chem. 2005, 70, 6548-51) in 97 ml of dichloromethane and 16.5 ml of pyridine are admixed dropwise at 0° C. with 14 ml (161 mmol) of propionyl chloride. The mixture is stirred for 16 hours and 100 ml of 2 M hydrochloric acid are added. The mixture is extracted with dichloromethane and the extracts are washed with water. Drying over sodium sulphate and the removal of the solvent in vacuo give 27.1 g of 2-chloro-3-fluorophenyl propionate. 30.1 g (133.7 mmol) of 2-chloro-3-fluorophenyl propionate in 42 ml of 1,2-dichlorobenzene are added dropwise to 19.6 g (133 mmol) of aluminum trichloride in 42 ml of 1,2-dichlorobenzene and the mixture is subsequently stirred at 100° C. for 18 hours. It is cooled, diluted with dichloromethane and poured cautiously onto a mixture of 2 M hydrochloric acid and ice. The phases are separated, extraction is carried out with dichloromethane and the extracts are washed with water and saturated sodium chloride solution and dried over sodium sulphate. The crude product is purified by column chromatography on silica gel (hexane/ethyl acetate 0-10%) to give 22.8 g of 1-(3-chloro-4-fluoro-2-hydroxyphenyl)propan-1-one. 22.8 g (112 mmol) of 1-(3-chloro-4-fluoro-2-hydroxyphenyl)propan-1-one are dissolved in 170 ml of acetone and the solution is admixed with 28.4 g (205 mmol) of potassium carbonate and 12.3 ml (198 mmol) of methyl iodide. The mixture is boiled under reflux for 4 hours and stirred at room temperature for 12 hours and then the solvent is largely removed. The residue is poured into water and extracted with diethyl ether. The extracts are washed with water and dried over sodium sulphate to give, following the removal of the solvent in vacuo, 24.4 g of 1-(3-chloro-4-fluoro-2-methoxyphenyl)propan-1-one. 63.3 g (969 mmol) of zinc dust and 1.33 g (4.77 mmol) of lead(II) chloride are suspended in 490 ml of THF and the suspension is admixed at 0° C. with 59 ml (846 mmol) of dibromomethane. The mixture is stirred at room temperature for a further 30 minutes and admixed dropwise at 0° C. with 113 ml (113 mmol) of a 1 M titanium(IV) chloride solution in dichloromethane. The cooling bath is removed and, after an hour, the reaction mixture is cooled again to 0° C. 124.4 g (113 mmol) of 1-(3-chloro-4-fluoro-2-methoxyphenyl)propan-1-one in 65 ml of THF are added dropwise. Stirring is carried out at room temperature for a further hour. The reaction mixture is diluted with diethyl ether and poured cautiously onto a mixture of 4 M hydrochloric acid and ice, the temperature not exceeding 5° C. The phases are separated, extraction is carried out with diethyl ether, the extracts are washed with water and saturated sodium chloride solution and dried over sodium sulphate, and the solvent is removed. The crude product is purified by column chromatography on silica gel (hexane/diisopropyl ether 0-20%) to give 12.7 g of 2-chloro-3-fluoro-6-(1-methylenepropyl)anisole

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