1: 93 percent / MCPBA / CH2Cl2 / 4 h / 10 °C 2: conc. aq. HI / diethyl ether / 0.5 h / -25 °C 3: boron trifluoride etherate / CH2Cl2 / 8 h / 0 °C 4: n-butyllithium / 1.) ether/hexane, from -50 deg C to -10 deg C, 2.) -10 deg C View Scheme