1: tetrahydrofuran / Ambient temperature 2: 96 percent / 5percent aqueous HF / tetrahydrofuran 3: Et3N / CH2Cl2 4: 71 percent / Bu4N(1+)F(1-)*3H2O / acetonitrile / 34 °C 5: 75 percent / 38percent HCl / ethane-1,2-diol / 2 h / 110 °C View Scheme