1: boron trifluoride diethyl etherate; triethylsilane / dichloromethane / 20 h / 50 °C 2: p-toluenesulfonyl chloride; pyridine / dichloromethane / 0.92 h / 0 - 20 °C 3: 1,8-diazabicyclo[5.4.0]undec-7-ene / toluene / 2 h / |Reflux 4: hydrogenchloride / methanol; water / 1 h / 20 °C View Scheme