1: sodium dihydrogenphosphate; sodium chlorite; 2-methyl-but-2-ene / water; tert-butyl alcohol 2: di-isopropyl azodicarboxylate; triphenylphosphine / toluene / 1.5 h 3: water; 2,3-dicyano-5,6-dichloro-p-benzoquinone / dichloromethane / 1 h / 20 °C 4: Grubb's 2nd generation catalyst / dichloromethane / 6 h / 40 °C 5: hydrogenchloride; water / tetrahydrofuran / 20 h View Scheme