1.1: triethylamine / potassium iodide / toluene / 24 h / boiling 2.1: sodium hydroxide / 20 °C 2.2: pH 2 3.1: 1-propanephosphonic acid cyclic anhydride / ethyl acetate / 2 h / 20 - 50 °C 4.1: hydrogen; acetic acid / 5 palladium on charcoal / ethanol / 6 h / 50 °C / 3750.38 Torr / Inert atmosphere 4.2: 20 °C 5.1: potassium carbonate / ethanol; water; acetone / 0.33 h / 28 - 32 °C View Scheme