bromine in tetrachloromethane T=-20°C;

magnesium bromide in tetrahydrofuran 72 h; Heating;

MgBr2(Et2O) in diethyl ether 120 h; Ambient temperature;

1: 90 percent / aq. sodium hydroxide, tetrabutylammonium bromide / CH2Cl2 / 3.5 h / Ambient temperature 2: 80 percent / butyllithium / tetrahydrofuran; hexane / -100 °C 3: 80 percent / magnesium bromide-diethyl ether / diethyl ether / 120 h / Ambient temperature View Scheme

1: 80 percent / butyllithium / tetrahydrofuran; hexane / -100 °C 2: 80 percent / magnesium bromide-diethyl ether / diethyl ether / 120 h / Ambient temperature View Scheme

1: 1.) butyl-lithium / 1.) THF, hexane, -78 deg C, 2 h, 2.) -78 deg C to room temperature, 1 h View Scheme

Yield given. Multistep reaction;