1.1: trifluoroacetic acid / dichloromethane / 20 °C / |Inert atmosphere 2.1: 1-hydroxy-pyrrolidine-2,5-dione; dicyclohexyl-carbodiimide / acetonitrile / 0.25 h / 20 °C / |Inert atmosphere 2.2: 20 °C / |Inert atmosphere 3.1: toluene-4-sulfonic acid / methanol / 1 h / 20 °C / |Inert atmosphere 4.1: palladium diacetate; ammonium formate / water / 20 °C / |Inert atmosphere View Scheme