1: With hydrogen bromide; sodium nitrite in water T=0°C; 0.166667 h; 2: With urea in water 0.0833333 h; 3: With hydrogen bromide; copper; copper(II) sulfate in water T=80°C; 1 h;

1.1: 81 percent / formic acid; Et3N / Pd/C / acetonitrile / 0.42 h / Heating 2.1: aq. HBr; NaNO2 / H2O / 0.17 h / 0 °C 2.2: urea / H2O / 0.08 h 2.3: 87 percent / CuSO4*5H2O; Cu; aq. HBr / H2O / 1 h / 80 °C View Scheme

1.1: 48 percent / ammonia; H2S / dioxane / 35 - 40 °C 2.1: NaNO2; AcOH; H2SO4 / H2O / 1 h / 20 - 25 °C 2.2: 76 percent / Cu2O / ethanol; H2O / 1.5 h / 20 °C 3.1: 81 percent / formic acid; Et3N / Pd/C / acetonitrile / 0.42 h / Heating 4.1: aq. HBr; NaNO2 / H2O / 0.17 h / 0 °C 4.2: urea / H2O / 0.08 h 4.3: 87 percent / CuSO4*5H2O; Cu; aq. HBr / H2O / 1 h / 80 °C View Scheme

1.1: NaNO2; AcOH; H2SO4 / H2O / 1 h / 20 - 25 °C 1.2: 76 percent / Cu2O / ethanol; H2O / 1.5 h / 20 °C 2.1: 81 percent / formic acid; Et3N / Pd/C / acetonitrile / 0.42 h / Heating 3.1: aq. HBr; NaNO2 / H2O / 0.17 h / 0 °C 3.2: urea / H2O / 0.08 h 3.3: 87 percent / CuSO4*5H2O; Cu; aq. HBr / H2O / 1 h / 80 °C View Scheme

sodium cyanide in dimethyl sulfoxide T=20°C; 2 h;