1: 100 percent / Na2SO3 / H2O / 2 h / 40 °C 2: 1) thionyl chloride, 2) liq.NH3 / 1,2-dimethoxy-ethane / 1) 1 h, 2)12 h 3: 32 percent / p-toluenesulfonic acid / ethyl acetate / 1 h / 105 - 110 °C 4: tributylphosphine / benzene / 24 h / Heating View Scheme