1: toluenesulfonic acid / benzene / 2 h / Heating 2: 92 percent / pyridinecarboxylic acid N-oxide, ceric ammonium nitrate / acetonitrile; H2O / 0.17 h 3: 95 percent / argentic oxide, nitric acid / acetone 4: 96 percent / trifluoroacetic acid, hydrochloric acid / 1,2-dimethoxy-ethane / 6 h / Ambient temperature View Scheme