1.1: iodine; silver sulphate / ethanol / 24 h / 25 °C 2.1: hydrogenchloride / diethyl ether; water / 0 °C 2.2: 0.17 h / 5 °C 2.3: 50 - 80 °C 3.1: tert.-butyl lithium / tetrahydrofuran / 1 h / -78 °C 3.2: 24 h View Scheme

Multistep reaction;