1: trifluoroacetic acid / dichloromethane; toluene / 2 h / 5 °C / |Large scale 2: triethylsilane; trifluoroacetic acid / dichloromethane; toluene / 6 h / |Reflux; |Large scale 3: potassium hydroxide; water / 60 °C / |Large scale View Scheme

caesium carbonate in acetonitrile T=20 - 25°C; Large scale; Concentration;