Example 3
4-Bromodibenzofuran
100.00 g (99%, 588.6 mmol) of dibenzofuran are dissolved in 800 ml of anhydrous THF and admixed at −40° C. with 400 ml (640.0 mmol) of n-BuLi (1.6M in hexane). The cooling bath is removed. The reaction solution is allowed to come to room temperature in a water bath within approx. 30 min and stirred for a further two hours. Thereafter, it is cooled to −78° C. and a solution of 160.34 g (99%, 844.9 mmol, 73.55 ml) of 1,2-dibromoethane in 80 ml of anhydrous THF is added dropwise. The cooling bath is removed, and the mixture is allowed to come to room temperature in a water bath within approx. 30 min and stirred for a further two hours. Subsequently, 60 ml of saturated sodium chloride solution are added cautiously (slightly exothermic reaction, temperature rise 1-2° C.). The organic phase is removed and freed of the solvent under reduced pressure. The oily red-brown residue is taken up in 900 ml of dichloromethane and washed successively with 500 ml of HCl solution (1N) and 400 ml of water. The organic phase is dried over magnesium sulfate and freed of the solvent under reduced pressure. In the course of cooling, a yellowish solid precipitates out, which is comminuted in a mortar and washed on a frit with 2×150 ml of isopropanol. After drying, 120.36 g of beige powder are obtained (according to GC and NMR: DBF/Br-DBF ratio=10/90, corresponds to 111.93 g of Br-DBF/76% yield). After removing the solvent, a further 15.84 g of a mixture of dibenzofuran and 4-bromodibenzofuran (comprises a further approx. 7.8 g/5% Br-DBF) are obtained from the isopropanol solution. This mixture can likewise be used in the further stages.
1H NMR (CDCl3, 500 MHz):
δ=7.92 (d, 3JH,H=7.8 Hz, 1H), 7.86 (dd, 3JH,H=7.7 Hz, 4JH,H=1.0 Hz, 1H), 7.65 (d, 3JH,H=8.2 Hz, 1H), 7.61 (dd, 3JH,H=7.8 Hz, 4JH,H=1.1 Hz, 1H), 7.50 (dt, 3JH,H=8.2 Hz, JH,H=1.3 Hz, 1H), 7.37 (dt, 3JH,H=7.8 Hz, JH,H=0.8 Hz, 1H), 7.21 (t, 3JH,H=7.8 Hz, 1H).
