1.1: n-BuLi / tetrahydrofuran / 0.25 h / -78 °C 1.2: 86 percent / tetrahydrofuran / 3 h / 23 °C 2.1: I-BuMgCl; Cl2TiCp2 / diethyl ether / 2 h / 0 - 23 °C 2.2: 81 percent / tetrahydrofuran / 2 h / 0 - 23 °C View Scheme

1: (Z)-6,10-dimethyl-5,9-undecadien-1-yne; trimethylaluminum With zirconocene dichloride in 1,2-dichloro-ethane T=23°C; 8 h; 2: With n-butyllithium in hexane T=-30°C; 3: formaldehyd in tetrahydrofuran; hexane T=23°C; 3 h; Further stages.;