1.1: O3 / CH2Cl2 / -78 °C 2.1: 34 percent / scandium triflate / acetonitrile / -20 - 0 °C 3.1: 53 percent / n-BuLi / tetrahydrofuran / -20 - 0 °C 4.1: potassium hexamethyldisilazane / tetrahydrofuran / -78 °C 4.2: PhSeCl / -23 °C 4.3: 31 percent / H2O2 / acetic acid View Scheme