Hydrochloric Acid → 2,3-Dichloro-6-(1-methylenepropyl)anisole

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20 g (122.7 mmol) of 2,3-dichlorophenol in 122 ml of dichloromethane and 13.8 ml of pyridine are admixed dropwise at 0° C. with 11.3 ml (128 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 25.2 g of 2,3-dichlorophenyl propionate. 25.2 g (115.2 mmol) of 2,3-dichlorophenyl propionate in 12 ml of 1,2-dichlorobenzene are added dropwise to 15.4 g (115.2 mmol) of aluminum trichloride in 12 ml of 1,2-dichlorobenzene and the mixture is subsequently stirred at 100° C. for 5 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 10-25%) to give 22.1 g of 1-(3,4-dichloro-2-hydroxyphenyl)propan-1-one. 22.1 g (101 mmol) of 1-(3,4-dichloro-2-hydroxyphenyl)propan-1-one are dissolved in 150 ml of acetone and the solution is admixed with 25.9 g (187 mmol) of potassium carbonate and 11.4 ml (183 mmol) of methyl iodide. The mixture is boiled under reflux for 16 hours and then the solvent is largely removed. The residue is poured into saturated sodium chloride solution and extracted with diethyl ether. The extracts are dried over sodium sulphate to give, following the removal of the solvent in vacuo, 23.2 g of 1-(3,4-dichloro-2-methoxyphenyl)propan-1-one. 29 g (444 mmol) of zinc dust and 0.69 g (2.5 mmol) of lead(II) chloride are suspended in 296 ml of THF and the suspension is admixed at 0° C. with 27.8 ml (174 mmol) of dibromomethane. The mixture is stirred at room temperature for a further 30 minutes and admixed dropwise at 0° C. with 49 ml (49 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. 11.5 g (49 mmol) of 1-(3,4-dichloro-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/ethyl acetate 0-30%) to give 5.8 g of 2,3-dichloro-6-(1-methylenepropyl)anisole.

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