1: 74 percent / N-chlorosuccinimide, 4 A molecular sieves / CH2Cl2 / Ambient temperature 2: 1.) n-BuLi, 2.) methanol / 1.) THF, hexane, -77 deg C, 1 h 3: 1.) n-BuLi / 1.) THF, hexane, -77 deg C, 5 min, 2.) from -77 deg C to RT 4: 1.) potassium tert-butoxide, n-BuLi / 1.) THF, hexane, from -35 deg C to -20 deg C, 30 min, 2.) THF, -35 deg C, 30 min View Scheme