1.1: dicyclohexylborane / tetrahydrofuran / -20 - 20 °C 1.2: 76 percent / NaOH; H2O2 / H2O / 0 - 30 °C 2.1: 90 percent / pyridinium p-toluenesulfonate / methanol / 50 - 55 °C 3.1: oxalyl chloride; dimethyl sulfoxide; triethylamine / CH2Cl2 / -60 - 0 °C 4.1: CH2Cl2 / 20 °C View Scheme