1: 80 percent / tetra-n-butylammonium bisulfate, 50percent KOH / CH2Cl2; H2O / 2 h / -20 °C 2: 100 percent / 10percent HCl / tetrahydrofuran / 2 h / Heating 3: 77 percent / trifluoroacetic anhydride / CH2Cl2 / 2 h / Heating 4: 52 percent / tetrahydrofuran / 1 h / -78 °C 5: 70 percent / 4N KOH / methanol / 5 h / Heating View Scheme