1: 73 percent / p-toluenesulfonic acid / benzene / 3 h / Heating 2: 78 percent / tetrabutylammonium bromide / benzene / 3 h / Heating 3: 30 percent / NaBH4 / ethanol / 0.17 h / Ambient temperature 4: Ba(OH)2 / H2O; ethanol / 3 h / 85 °C View Scheme

toluene-4-sulfonic acid in benzene 3 h; Heating;