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With exclusion of oxygen, a solution of 14.0 g (67.63 mmol) of 1-bromo-4-(difluoromethyl)benzene [CAS 51776-71-7] and 25.3 g (142 mmol) of N-bromosuccinimide (NBS) in 190 ml of tetrachloromethane is irradiated with a sun lamp. During this, the solvent reaches its boiling point. It is irradiated under reflux for 24 hours. The mixture is then allowed to cool to room temperature and precipitated succinimide is filtered off. The filtrate is again mixed with 25 g of NBS and irradiated once more with exclusion of oxygen under reflux for 24 hours. Cooling is followed by filtration again, and the filtrate is concentrated to dryness. 18 g of an orange-colored oil are obtained as crude product, which is purified further by vacuum distillation at 13 mmHg. 12.7 g (44.4 mmol, 66% yield) of a colorless oil are obtained.

1. customIt is irradiated
2. temperatureunder reflux for 24 hours
3. customprecipitated succinimide
4. filtrationis filtered off
5. additionThe filtrate is again mixed with 25 g of NBS
6. customirradiated once more with exclusion of oxygen
7. temperatureunder reflux for 24 hours
8. temperatureCooling
9. filtrationis followed by filtration again
10. concentrationthe filtrate is concentrated to dryness