Tamao-Fleming oxidation stereoselectivity

Hunt and Roush <1995TL501> achieved a synthesis of swansonine 230 via a stereoselective allylation of a silyl allylboronate derived from tartaric acid followed by a Tamao-Fleming oxidation to introduce the C-2 hydroxy functionality (Scheme 54). 

For the last two decades, the use of the platinum- or rhodium-catalyzed intramolecular hydrosilylation/Tamao-Fleming oxidation sequence has been well recognized as a powerful method for the stereoselective synthesis of various structurally diverse alcohols (1,3-diols, 2-alkoxy-l,3-diols, and 2-aminoalcohols) and ketone derivatives (/3-hydroxyketones, y-hydroxyketones, o, /3-dihydroxyketones, and a,y-dihydroxyketones) from simple and readily available starting materials such as substituted allyl or propargyl alcohols and their homologues (4,177). Selected applications are presented in equations (24-26). 

Scheme 3-76. Stereoselective triol synthesis through palladium-catalyzed intramolecular disilylation of alkenes followed by the Tamao-Fleming oxidation.

Exocyclic bis-silylated olefins have been constructed through the Pd(OAc)2-catalyzed reaction of alkynes with a tethered disi-lanyl group. The reactions are carried out in the presence of a tert-alkyl isocyanide, although the precise role of this ligand is unclear. Diimide reduction of the disilylated alkene so-formed followed by Fleming-Tamao-type oxidation of the two C-Si bonds in the saturated product then affords 1,2,4-triols in a stereoselective manner (eq 83).l ... 

In the laboratory of F.G. West, the stereoselective silyl-directed [1,2]-Stevens rearrangement of ammonium ylides was investigated as a potential key step toward the enantioselective synthesis of various hydroxylated quinolizidines. The dimethylphenylsilyl group served as a surrogate for one of the hydroxyl groups in the product. The Fleming-Tamao oxidation was performed under Denmark s conditions to avoid oxidation of the tertiary amine to the corresponding A/-oxide, and the desired quinolizidine did was obtained in 81% yield. 

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