1: phenyl isocyanate; triethylamine / toluene / 4 h / 20 - 80 °C 2: tetrabutyl ammonium fluoride / tetrahydrofuran / 0.58 h / 0 °C 3: tetrachloromethane; triphenylphosphine / dichloromethane / 0.33 h / 20 - 50 °C 4: lithium hydroxide hydrate; water / tetrahydrofuran / 19 h / 20 °C View Scheme