Lead tetrabenzoate ketones

Lead(IV) salts will a-oxygenate enol ethers as they do enols vide supra), although in this case the process involves bisoxygenation of the unsaturated Ullage and subsequent hydrolysis. For example, the combination of lead tetrabenzoate and triethylammonium fluoride at 0-25 C effects efficient a-benzoyl-oxylation, e.g. (68) to (69). 0, y-Unsaturated ketones are also successfully oxidized, e.g. (70) to (71). The correspon ng LTA a-acetoxylations are possible, but the benzoate salt remains the transition metal reagent of choice for these substrates.These reactions appear to be uniformly efficient and perluq)S deserve wider synthetic tq>plication. 

Other reagents have been utilized for this transformation. For example, lead tetrabenzoate (with fluoride-induced hydrolysis of (136) and (137). However, success is restricted to acyclic ketones. Where cyclic dienol ethers are employed, products derived from a-oxidation are obtained. ... 

Regiospecific preparation of a-benzoyloxy carbonyl compounds by lead tetrabenzoate (LTB) oxidation of the trimethylsilyl enol ethers is possible. Similarly, a-thiolated ketones can be prepared from a disulfide. 71... 

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