Lead Tetraacetate (contains Acetic Acid)

Typical Procedure:
To a solution of olefine 1 (11.9 mg, 0.030 mmol) and DMAP (7.33 mg, 0.060 mmol, 2 eq.) in t-BuOH (100 µL) is added a solution of OsO₄ (7.62 mg, 0.030 mmol, 1 eq.) in water (200 µL). The orange-red solution is stirred at rt for 5-10 min. Solid Na₂SO₃ (19 mg, 0.15 mmol, 5 eq.) is added. The resulting mixture is applied directly to preparative TLC (CHCl₃ : MeOH : NH₄OH = 25 : 10 : 1) and diol is collected by washing silica gel with a mixture of CHCl₃ : MeOH = 2 : 1. Concentration under reduced pressure (< 25 ℃) affords the slightly unstable diol 2, which is dissolved in CH₂Cl₂ (2 mL). The solution then is cooled to -20 ℃ and AcOH (9.0 mg, 8.6 µL, 5 eq.) is added, followed by solid Pb(OAc)₄ (11 mg, 0.025 mmol) in portions. TLC (CH₂Cl₂ : MeOH = 1 : 1 and 25 : 1) monitors the end of the reaction. The resulting yellow solution is stirred at -20 ℃ for 5-10 min, washed with water, saturated NaHCO₃ and brine, dried over Na₂SO₄ and evaporated under reduced pressure to give 3 (8.5 mg, Y. 71%) of silica gel labile ketone as a yellow powder.