1: DBU, MeOH / 20 h / -20 °C 2: 23 h / Ambient temperature 3: Tf2O, (i-Pr)2NEt / toluene / 1 h / 50 °C 4: 95 percent / HCl / methanol / 40 h / Ambient temperature View Scheme

1: 100 percent / 14 h / 50 °C 2: 80 percent / Bu3SnH / toluene / 9 h / Heating 3: 86 percent / CBr4, MeOH / 19 h / Heating 4: 100 percent / NaOH, H2O / 13 h / Ambient temperature View Scheme

1: DBU, MeOH / 20 h / -20 °C 2: 23 h / Ambient temperature 3: Tf2O, (i-Pr)2NEt / toluene / 1 h / 50 °C 4: 95 percent / HCl / methanol / 40 h / Ambient temperature 5: 96 percent / NaOH, H2O / tetrahydrofuran / 1 h / Ambient temperature View Scheme