1: With hydrogenchloride; sodium nitrite 0.5 h; cooling; 2: With potassium iodide in water T=40°C; 0.166667 h;

sodium hydroxide; potassium hexacyanoferrate(III) in water T=20°C; Jacobson's cyclizaation; Cooling with ice;

1.1: 64 percent / H2SO4; HNO3 / 3 h / 20 °C 2.1: 92 percent / HCOONH2 / Pd/C / tetrahydrofuran; methanol / 72 h / 20 °C 3.1: aq. HCl; NaNO2 / 0.5 h / cooling 3.2: 79 percent / aq. KI / H2O / 0.17 h / 40 °C View Scheme

1.1: 92 percent / HCOONH2 / Pd/C / tetrahydrofuran; methanol / 72 h / 20 °C 2.1: aq. HCl; NaNO2 / 0.5 h / cooling 2.2: 79 percent / aq. KI / H2O / 0.17 h / 40 °C View Scheme

1: P2S5 2: K3<Fe(CN)6>; aqueous NaOH View Scheme

1: iodine; sodium hydrogencarbonate / water / 12 - 20 °C 2: pyridine / tetrahydrofuran / Heating 3: aluminum oxide; tetraphosphorus decasulfide; sulfur / dichloromethane / 10 h / Reflux 4: sodium hydroxide; potassium hexacyanoferrate(III) / water / 20 °C / Cooling with ice View Scheme

1: pyridine / tetrahydrofuran / Heating 2: aluminum oxide; tetraphosphorus decasulfide; sulfur / dichloromethane / 10 h / Reflux 3: sodium hydroxide; potassium hexacyanoferrate(III) / water / 20 °C / Cooling with ice View Scheme