1: 87 percent / diphenylphosphoryl azide, 1,8-diazabicyclo<5.4.0>undec-7-ene / 23 h / Ambient temperature 2: 78 percent / H2S, pyridine / 1.5 h / Ambient temperature 3: diisopropylethylamine / dimethylformamide / 96 h / Ambient temperature 4: aq. NaOH / methanol / Ambient temperature View Scheme

diphenylphosphoranyl azide; 1,8-diazabicyclo[5.4.0]undec-7-ene 23 h; Ambient temperature;

ammonia; triphenylphosphine; diethylazodicarboxylate in toluene T=0°C; 14 h;

1: 87 percent / diphenylphosphoryl azide, 1,8-diazabicyclo<5.4.0>undec-7-ene / 23 h / Ambient temperature 2: 78 percent / H2S, pyridine / 1.5 h / Ambient temperature View Scheme