1: 100 percent / pyridine 2,6-dicarboxylic acid, Ce(NH4)2(SO4)2 / acetonitrile; H2O / 2 h 2: 100 percent / methanol / 2 h 3: 75 percent / CH3ONa / toluene / 2 h 4: 81 percent / toluene / 10 h / Heating View Scheme

1: 100 percent / pyridine 2,6-dicarboxylic acid, Ce(NH4)2(SO4)2 / acetonitrile; H2O / 2 h 2: 100 percent / methanol / 2 h 3: 75 percent / CH3ONa / toluene / 2 h 4: 35 percent / t-BuOK / toluene; 2-methyl-propan-2-ol / 1 h / 0 °C 5: 100 percent / toluene / 0.5 h / Heating View Scheme