1.1: n-BuLi / tetrahydrofuran; hexane / 2 h / -78 - 20 °C 1.2: 54 percent / tetrahydrofuran; hexane / -78 - 20 °C 2.1: 59 percent / manganese dioxide / CH2Cl2 / 20 °C 3.1: 58 percent / PPh3 / CH2Cl2 / 20 °C 4.1: 72 percent / n-BuLi / hexane / 0.5 h / -78 - -40 °C View Scheme

triphenylphosphine in dichloromethane T=0°C; 0.5 h;

triphenylphosphine in dichloromethane T=20°C;

in dichloromethane 0.5 h; Ambient temperature;

zinc 1.) CH2Cl2, 23 deg C, 30 h, 2.) 10 deg C - room temp, 2 h; Yield given. Multistep reaction;