1: ((4-bromopent-4-en-1-yl)oxy)(tert-butyl)dimethylsilane With tert.-butyl lithium in tetrahydrofuran; pentane T=-78°C; 0.5 h; 2: N,N-dimethyl-formamide in tetrahydrofuran; pentane T=-78°C; 3 h;

anhydrous diethylamine hydrochloride in 1,2-dichloro-ethane T=70°C;

1.1: 15.74 g / Et3N; DBU / CH2Cl2 2.1: tert-butyllithium / tetrahydrofuran; pentane / 0.5 h / -78 °C 2.2: 99 percent / tetrahydrofuran; pentane / 3 h / -78 °C View Scheme

1.1: sodium hydride / tetrahydrofuran / 0.75 h / 0 - 20 °C 1.2: 12 h / 0 - 20 °C 2.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.75 h / -78 °C 3.1: pyrrolidine; propionic acid / isopropyl alcohol / 24 h / 45 °C View Scheme

1.1: sodium hydride / tetrahydrofuran / 0.75 h / 0 - 20 °C 1.2: 12 h / 0 - 20 °C 2.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 0.75 h / -78 °C 3.1: pyrrolidine; propionic acid / isopropyl alcohol / 24 h / 45 °C View Scheme