1: carbon tetrabromide With triphenylphosphine in dichloromethane T=20°C; 5 h; 2: 1-triisopropylsilanyl-nona-1,4-diyn-3-one in dichloromethane 2 h;

1.1: PCC; molecular sieves 4 Angstroem; celite / CH2Cl2 / 20 °C 2.1: triphenylphosphine / CH2Cl2 / 5 h / 20 °C 2.2: 786 mg / CH2Cl2 / 2 h View Scheme

1.1: BuLi / hexane; tetrahydrofuran / 0.5 h / -78 °C 1.2: 91 percent / tetrahydrofuran; hexane / -78 - 20 °C 2.1: PCC; molecular sieves 4 Angstroem; celite / CH2Cl2 / 20 °C 3.1: triphenylphosphine / CH2Cl2 / 5 h / 20 °C 3.2: 786 mg / CH2Cl2 / 2 h View Scheme

1.1: BuLi / hexane; tetrahydrofuran / 0.5 h / -78 °C 1.2: 91 percent / tetrahydrofuran; hexane / -78 - 20 °C 2.1: PCC; molecular sieves 4 Angstroem; celite / CH2Cl2 / 20 °C 3.1: triphenylphosphine / CH2Cl2 / 5 h / 20 °C 3.2: 786 mg / CH2Cl2 / 2 h View Scheme