sodium dithionite in diethyl ether; water 1 h;

ammonium cerium(IV) nitrate in solid 2 h; ultrasonic irradiation;

1: NaH / diethyl ether; tetrahydrofuran / 15 h / 23 °C 2: 73 percent / piperidine / tetrakis(triphenylphosphine)palladium(0), copper(I) iodide / 15 h / 100 °C 3: 87 percent / KF, H2O / dimethylformamide / 4 h / 23 °C 4: 44 percent / n-BuLi / tetrahydrofuran / 1.) -78 deg C, 1 h, 2.) 23 deg C, 48 h 5: 73 percent / cerium(IV) ammonium nitrate / acetonitrile; H2O / 0.5 h / 23 °C 6: 79 percent / 1,4-cyclohexadiene / benzene-d6 / 40 °C View Scheme