1: 72 percent / DDQ / benzene / 3 h / Heating 2: 70 percent / polyphosphoric acid / 2 h / 70 - 125 °C 3: sodium borohydride / tetrahydrofuran / 2 h / Ambient temperature 4: 83 percent / paratoluenesulfonic acid / toluene / 1 h / Heating View Scheme

1: 72 percent / DDQ / benzene / 3 h / Heating 2: 70 percent / polyphosphoric acid / 2 h / 70 - 125 °C 3: 93 percent / hydrazin monohydrate, KOH / 1,2-dimethoxy-ethane; ethane-1,2-diol / 0.5 h / Heating View Scheme

2,3-dicyano-5,6-dichloro-p-benzoquinone in benzene 3 h; Heating;

1: 72 percent / DDQ / benzene / 3 h / Heating 2: 70 percent / polyphosphoric acid / 2 h / 70 - 125 °C View Scheme