1: p-TsOH / 3 h / 18 °C 2: 1.) BuLi, 2.) Hg(OAc)2, H2O / 1.) THF, 18 deg C, 10 h, 2.) THF, 18 deg C, 5 h 3: 92 percent / Dess-Martin periodinane / CH2Cl2 / 1.5 h / 18 °C 4: 30 percent / HCl, H2O / 18 h / 18 °C View Scheme