1.1: pyridine / dichloromethane / 0.5 h / -10 - 0 °C / Inert atmosphere 2.1: sodium azide / water; acetone / 15 h / 20 °C 3.1: 2,6-dimethylpyridine / chloroform / 5 h / Inert atmosphere; Reflux 4.1: trifluoroacetic acid / dichloromethane / 1 h / 20 °C / Inert atmosphere; Cooling with ice 4.2: 55 °C / Inert atmosphere View Scheme