1: 45 percent / TMSOTf / various solvent(s) / -78 - -50 °C 2: 62 percent / TMSOTf; Et3N / CH2Cl2 / 0 - 10 °C 3: HCl View Scheme

1.1: 45 percent Turnov. / trimethylsilyltriflate / various solvent(s) / -78 - -60 °C 2.1: 62 percent / Et3N; trimethylsilyl triflate / CH2Cl2 / 2 h / 0 °C 3.1: HCl / diethyl ether / 1 h / 20 °C 3.2: 98 percent / 4-(dimethylamino)pyridine; Et3N / diethyl ether / 10 h / 25 °C View Scheme