1: With boron tribromide in dichloromethane T=20°C; Inert atmosphere; 2: With methanol in dichloromethane T=20°C; Inert atmosphereReflux;

1.1: lithium hexamethyldisilazane / tetrahydrofuran / 1 h / -20 °C / Inert atmosphere 1.2: -20 °C / Inert atmosphere 2.1: trimethylsilyl trifluoromethanesulfonate / dichloromethane / 1 h / 20 °C / Inert atmosphere 3.1: boron tribromide / dichloromethane / 20 °C / Inert atmosphere 3.2: 20 °C / Inert atmosphere; Reflux View Scheme

1.1: trimethylsilyl trifluoromethanesulfonate / dichloromethane / 1 h / 20 °C / Inert atmosphere 2.1: boron tribromide / dichloromethane / 20 °C / Inert atmosphere 2.2: 20 °C / Inert atmosphere; Reflux View Scheme

1.1: 4-(N,N-dimethlyamino)pyridine; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride / dichloromethane / 24 h / 20 °C / Inert atmosphere 2.1: lithium hexamethyldisilazane / tetrahydrofuran / 1 h / -20 °C / Inert atmosphere 2.2: -20 °C / Inert atmosphere 3.1: trimethylsilyl trifluoromethanesulfonate / dichloromethane / 1 h / 20 °C / Inert atmosphere 4.1: boron tribromide / dichloromethane / 20 °C / Inert atmosphere 4.2: 20 °C / Inert atmosphere; Reflux View Scheme