1: boron trifluoride etherate / CH2Cl2 / 2 h / 0 °C 2: 66 percent / diethyl ether; 1,2-dimethoxy-ethane / 40 - 50 °C 3: 97 percent / potassium t-butoxide / diethyl ether / 16 h / 1.) ether, 16 h 4: 87 percent / NaCl, water / dimethylsulfoxide / 10 h / 150 °C 5: 98 percent / potassium t-butoxide / diethyl ether / 0.5 h / 0 °C View Scheme