1: 91 percent / pyridine / CH2Cl2 / 5 h / 0 °C 2: 90 percent / thiourea / methanol / 2 h / Heating 3: 80 percent / 4A molecular sieves, N-iodosuccinimide, silver triflate / CH2Cl2; toluene / 0.17 h / 0 °C 4: 83 percent / NaOMe, MeOH / CH2Cl2 / 5 h / Ambient temperature View Scheme