boron trifluoride diethyl etherate in diethyl ether 3 h; Ambient temperature;

1: 93 percent / boron trifluoride etherate / diethyl ether / 2 h / -30 °C 2: 69 percent / ethanol / 2 h / Heating 3: 21 percent / tert-butyllithium / pentane; tetrahydrofuran / 1.) -78 deg C, 24 h, 2.) room temperature 4: 44 percent / 550 °C / 0.1 Torr View Scheme