air

1: 71 percent / dichlorodicyanquinone (DDQ) / tetrahydrofuran; H2O / -78 °C 2: 65.4 percent / 6 N aq. NaOH / 3 h / 108 °C 3: 85 percent / sulfur / xylene / 17 h / Heating 4: 63 percent / methanol; diethyl ether / -78 - 20 °C View Scheme