boron trifluoride diethyl etherate in diethyl ether -78 deg C to RT. within 2 h;

zinc dibromide in dichloromethane -95 deg C 1 h, RT., 2 day;

zinc dibromide

T=-78°C;

1: 5.7 g / n-butyl-lithium, diisopropylamide / tetrahydrofuran; hexamethylphosphoric acid triamide; hexane / 0.33 h / -78 °C 2: 94 percent / tetrahydrofuran / -78 deg C, 1 h, 20 deg C, 1 h 3: 93 percent / zinc bromide / CH2Cl2 / -95 deg C 1 h, RT., 2 day View Scheme

1: 95 percent / NBS / 110 - 115 °C 2: 74 percent / anhydr. ZnBr2 / xylene / 8 h / Heating 3: 5.7 g / n-butyl-lithium, diisopropylamide / tetrahydrofuran; hexamethylphosphoric acid triamide; hexane / 0.33 h / -78 °C 4: 94 percent / tetrahydrofuran / -78 deg C, 1 h, 20 deg C, 1 h 5: 93 percent / zinc bromide / CH2Cl2 / -95 deg C 1 h, RT., 2 day View Scheme

1: 74 percent / anhydr. ZnBr2 / xylene / 8 h / Heating 2: 5.7 g / n-butyl-lithium, diisopropylamide / tetrahydrofuran; hexamethylphosphoric acid triamide; hexane / 0.33 h / -78 °C 3: 94 percent / tetrahydrofuran / -78 deg C, 1 h, 20 deg C, 1 h 4: 93 percent / zinc bromide / CH2Cl2 / -95 deg C 1 h, RT., 2 day View Scheme

1: 94 percent / tetrahydrofuran / -78 deg C, 1 h, 20 deg C, 1 h 2: 93 percent / zinc bromide / CH2Cl2 / -95 deg C 1 h, RT., 2 day View Scheme