oxygen; anhydrous cobalt diacetate

1: 1.) LiBr, diisopropylamine, BuLi / 1.) THF, -78 deg C, 30 min, 2.) THF, -78 deg C, 2 h 2: 76 percent / Me3SiSnBu3, (Et2N)3SSiMe3F2 / dimethylformamide / 1 h / 0 °C View Scheme