1: diphenyl phosphoryl azide; triethylamine / toluene / 0.33 h / 20 °C 2: diphenyl phosphoryl azide; triethylamine / toluene / 1 h / 65 °C 3: 1.5 h / 65 °C 4: 2-hydroxy-pyridine / tert-butyl methyl ether / 65 °C 5: 10 palladium on activated charcoal; hydrogen View Scheme

1: diphenyl phosphoryl azide; triethylamine / toluene / 0.33 h / 20 °C 2: diphenyl phosphoryl azide; triethylamine / toluene / 1 h / 65 °C 3: 1.5 h / 65 °C 4: 2-hydroxy-pyridine / tert-butyl methyl ether / 65 °C View Scheme