sulfuric acid; sodium nitrite in water T=0°C; Reflux;

1.1: UHP; trifluoroacetic anhydride / dichloromethane / 0 - 20 °C 2.1: tetrahydrofuran / -60 °C / Inert atmosphere 2.2: -60 - 20 °C / Inert atmosphere 3.1: iron; acetic acid / 5 h / 110 °C 4.1: sulfuric acid; sodium nitrite / water / 0 °C / Reflux View Scheme

1: iron; acetic acid / 5 h / 110 °C 2: sulfuric acid; sodium nitrite / water / 0 °C / Reflux View Scheme

1.1: tetrahydrofuran / -60 °C / Inert atmosphere 1.2: -60 - 20 °C / Inert atmosphere 2.1: iron; acetic acid / 5 h / 110 °C 3.1: sulfuric acid; sodium nitrite / water / 0 °C / Reflux View Scheme

1.1: sulfuric acid / Heating 2.1: UHP; trifluoroacetic anhydride / dichloromethane / 0 - 20 °C 3.1: tetrahydrofuran / -60 °C / Inert atmosphere 3.2: -60 - 20 °C / Inert atmosphere 4.1: iron; acetic acid / 5 h / 110 °C 5.1: sulfuric acid; sodium nitrite / water / 0 °C / Reflux View Scheme

1: Raney Ni alloy, 2 N aq. NaOH / ethanol / 1 h / Ambient temperature 2: 1.) oxygen, tetraphenylporphine, 2.) triphenylphosphine / 1.) CH2Cl2, -70 deg C, irradiation, 2 h, 2.) -70 deg C, 10 min View Scheme

oxygen; 5,15,10,20-tetraphenylporphyrin; triphenylphosphine 1.) CH2Cl2, -70 deg C, irradiation, 2 h, 2.) -70 deg C, 10 min; Yield given. Multistep reaction;