1: dichloromethane / 2 h / 20 °C 2: sodium hydride / tetrahydrofuran / 1 h / 0 °C 3: N-bromosuccinmide; 2,2'-azo-bisisobutyronitrile / benzene / 5 h / 70 °C 4: potassium tert-butylate / tert-butyl alcohol / 0.25 h / 70 - 85 °C View Scheme