1: 25.1 g / 1 N aq. NaOH / methanol / 1.5 h / Ambient temperature 2: 57 percent / diethylaminosulfur trifluoride (DAST), pyridine / CH2Cl2 / 3 h / Heating 3: 66 percent / pyridinium p-toluenesulfonate (PPTS), C2H5OH / 24 h / 50 °C View Scheme

1: 25.1 g / 1 N aq. NaOH / methanol / 1.5 h / Ambient temperature 2: 57 percent / diethylaminosulfur trifluoride (DAST), pyridine / CH2Cl2 / 3 h / Heating 3: 66 percent / pyridinium p-toluenesulfonate (PPTS), C2H5OH / 24 h / 50 °C View Scheme

1: 25.1 g / 1 N aq. NaOH / methanol / 1.5 h / Ambient temperature 2: 57 percent / diethylaminosulfur trifluoride (DAST), pyridine / CH2Cl2 / 3 h / Heating 3: 1.) 4-chlorophenyl phosphorodichloridate, 1,2,4-triazole, pyridine, 2.) conc. NH4OH / 1.) RT, 2 d, 2.) dioxane, RT, 1 d 4: 66 percent / pyridinium p-toluenesulfonate (PPTS), C2H5OH / 24 h / Heating View Scheme