1.1: 94 percent / DMAP; pyridine / 16 h / 20 °C 2.1: 98 percent / TBAF / tetrahydrofuran / 3 h / Heating 3.1: 72 percent / PCC / CH2Cl2 / 0.5 h / 20 °C 4.1: p-toluenesulfonylhydrazine; Na2SO4 / ethanol / 3.5 h / 100 °C 4.2: 14 percent / NaBH3CN; p-toluenesulfonic acid monohydrate / dimethylformamide; tetrahydrothiophene 1,1-dioxide / 1 h / 100 °C 5.1: 70 percent / K2CO3 / methanol / 13 h / 50 °C View Scheme