1.1: 92 percent / Zn; AcOH / diethyl ether / 1 h / 23 °C 2.1: 4-formyl-1-methylpyridinium benzenesulfonate / CH2Cl2; dimethylformamide / 0.17 h / 23 °C 2.2: DBU / CH2Cl2; dimethylformamide / 0.25 h / 23 °C 2.3: 53 percent / aq. oxalic acid / CH2Cl2; dimethylformamide / 0.5 h / 23 °C 3.1: 97 percent / NaOAc / ethanol / 3 h / 23 °C 4.1: 92 percent / aq. AgNO3 / acetonitrile / 19 h / 23 °C View Scheme