1: triphenylphosphine; diethylazodicarboxylate / tetrahydrofuran / 14 h / -23 - 20 °C 2: tetrabutyl ammonium fluoride / tetrahydrofuran / 2 h / 20 °C 3: hydrogenchloride; water / tetrahydrofuran / 8 h / |Reflux View Scheme

1: triphenylphosphine; diethylazodicarboxylate / tetrahydrofuran / 14 h / -23 - 20 °C 2: tetrabutyl ammonium fluoride / tetrahydrofuran / 2 h / 20 °C 3: hydrogenchloride; water / tetrahydrofuran / 8 h / |Reflux View Scheme

1: 81 percent / pyridine; air / Cu(OAc)2 / CH2Cl2 / 44 h / 20 °C 2: 87 percent / AcOH; aq. HCl / 17 h / 90 °C View Scheme