1.1: triethylamine; 4-(N,N-dimethlyamino)pyridine / 1 h / 0 °C 2.1: sodium hydride / dichloromethane; dimethyl sulfoxide; mineral oil / 8 h / 20 °C 3.1: boron trifluoride diethyl etherate / dichloromethane / 0.37 h / -15 °C 4.1: caesium carbonate / dimethyl sulfoxide / 0.25 h / 80 °C 4.2: 0.33 h / 80 °C View Scheme

1.1: triethylamine; 4-(N,N-dimethlyamino)pyridine / 1 h / 0 °C 2.1: sodium hydride / dichloromethane; dimethyl sulfoxide; mineral oil / 8 h / 20 °C 3.1: boron trifluoride diethyl etherate / dichloromethane / 0.37 h / -15 °C 4.1: caesium carbonate / dimethyl sulfoxide / 0.25 h / 80 °C 4.2: 0.33 h / 80 °C 5.1: phosphoric acid / ethyl acetate; ethanol / 2 h / 50 °C View Scheme