Bromine → 3-Bromo-6,7,8,9-tetrahydro-5H-benzo(7)annulen-5-one

A 3-neck 250 mL flask fitted with a condenser was charged with aluminum trichloride (45.0 g, 337 mmol) which was then heated to 75° C. under nitrogen. 6,7,8,9-Tetrahydro-5H-benzo[7]annulen-5-one (20.0 g, 125 mmol) was added slowly dropwise via additional funnel. After complete addition, a dark brown slurry was formed. After stirring for 20 min, bromine (8.36 ml, 162 mmol) was added dropwise very slowly at 75° C., and the reaction mixture was stirred at 75° C. for an additional 20 min. The hot mixture was slowly poured into 400 g of ice and 30 mL of concentrated HCl. The resulting mixture was stirred for 30 min, then extracted with diethyl ether (3×400 mL). The ethereal extract was concentrated and the residue was purified using silica gel column chromatography (hexanes-10% EtOAc) to afford 3-bromo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-one (8.3 g, 28%). 1H NMR (500 MHz, chloroform-d) δ 7.86 (d, J=2.1 Hz, 1H), 7.54 (dd, J=8.2, 2.1 Hz, 1H), 7.10 (d, J=8.2 Hz, 1H), 2.94-2.88 (m, 2H), 2.80-2.72 (m, 2H), 1.94-1.80 (m, 4H).