1: dimethylsulfide borane complex / tetrahydrofuran / 0 °C / |Inert atmosphere; |Reflux 2: pyridine; thionyl chloride / tetrahydrofuran / 0 - 5 °C 3: dimethyl sulfoxide / 1.5 h / |Inert atmosphere 4: water; Ba(OH)2 / 1,4-dioxane / 30 h / |Reflux; |Inert atmosphere View Scheme