1: 59 percent / BF3*Et2O / CH2Cl2 / 0 °C 2: diisobutylaluminum hydride (DIBAL) / toluene / -78 °C 3: 53 percent / sodium cyanoborohydride (NaCNBH3) / 2-methyl-propan-2-ol 4: N-chlorosuccinimide, AgNO3 / acetonitrile View Scheme