1: 95 percent / MnO2 / CHCl3 / 72 h / Ambient temperature 2: 97 percent / potassium t-butoxide / diethyl ether / 16 h / 1.) ether, 16 h 3: 87 percent / NaCl, water / dimethylsulfoxide / 10 h / 150 °C 4: 98 percent / potassium t-butoxide / diethyl ether / 0.5 h / 0 °C View Scheme