1: caesium carbonate / toluene / 1 h / 20 °C / Inert atmosphere 2: potassium hydroxide / methanol; water / 1 h / 20 °C 3: ammonium cerium (IV) nitrate; sodium hydrogencarbonate / tetrahydrofuran / 1 h / 20 °C / Inert atmosphere 4: boron tribromide / dichloromethane / 1.5 h / -78 - -20 °C / Inert atmosphere View Scheme