1.1: 90 percent / dimethylsulfoxide 2.1: 82 percent / aq. NaOH / methanol / Heating 3.1: 92 percent / Me3SiCl / 20 °C 4.1: O3 / CH2Cl2 / -78 °C 4.2: 64 percent / Me2S / CH2Cl2 / 4 h / 25 °C View Scheme