Bromine → 4-bromo-5,6,7,8-tetrahydro-1(2H)-Isoquinolinone

32.4 g (217 mmol) of tetrahydroisoquinolinone (compound 5) is dissolved in 300 ml of chloroform at 5° C. and then 11.2 ml (34.7 g, 217 mmol) of bromine, dissolved in 150 ml of chloroform, are added dropwise over the course of 1 h. The mixture is stirred while cooling in ice for a further hour and then neutralized with 150 ml of saturated NaHCO3 solution and filtered with suction. The organic phase of the filtrate is extracted with dichloromethane and concentrated. The residue is mixed with ethyl acetate, filtered off with suction and dried together with the first residue in a vacuum drying oven at 45° C. 47.7 g (96%) of colorless bromide are obtained.