1: 49 percent / NaOH / dimethylsulfoxide / 1 h / 80 °C 2: 84 percent / H2O; dimethylsulfoxide / 3 h / 55 °C 3: 98 percent / Na2WO4*2H2O, aq. H2O2, aq. HCl / toluene / 1 h / 60 °C 4: 42 percent / 0.5 M aq. NaOH / 14 h / 45 °C View Scheme