4-Bromo-2-fluorotoluene → 4,5-Dihydro-5,5-dimethyl-2-(3'-fluoro-4'-methyl-biphenyl-2-yl)oxazole

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반응 단계

14.7 g (605.7 mol) of magnesium filings are initially introduced into 50 ml of analytical grade tetrahydrofuran under argon, and 117.7 g (623 mmol) of 4-bromo-2-fluorotoluene in 500 ml of analytical grade tetrahydrofuran are added, while stirring. A clear solution forms at 35°-40° C. within 2 hours. A solution of 74.0 g (360.5 mmol) of the compound from Example II in 500 ml of analytical grade tetrahydrofuran is added dropwise at room temperature and the mixture is subsequently stirred at about 25° C. for 16 hours, initially with gentle cooling. The solvent is evaporated off and the crude product is subsequently rinsed in 600 ml of ethyl acetate and 800 ml of saturated ammonium chloride solution at 10° C., dried with sodium sulphate and evaporated in vacuo. For purification, the product is taken up in 600 ml of ether, any solid residue is filtered off with suction and the crude product is extracted into the aqueous phase by several extractions with 2M hydrochloric acid. This aqueous phase is covered with a layer of ether and brought to pH 13 with sodium hydroxide solution. After three extractions with ether, the product phase is dried with sodium sulphate and evaporated and the residual solvent is removed under a high vacuum.

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