Saegusa oxidation, silyl enol

By Saegusa-Ito oxidation " Dehydrosilylation of silyl enol ethers with... 

The first total synthesis of the marine polycyclic ether toxin (-)-gambierol was accomplished in the laboratory of M. Sasaki. The introduction of the a,(3-unsaturation into the seven-membered H ring of the FGH tricyclic subunit proved to be problematic, because both the conventional selenium-based method and the Nicolaou oxidation with IBX failed. However, when the seven-membered ketone was treated with LiHMDS in the presence of TMSCI and EtsN, the corresponding silyl enol ether was formed, which was oxidized under Saegusa conditions to give the desired cyclic enone in high yield. Because of the small scale of the reaction, a large excess of Pd(OAc)2 was used in acetonitrile so the presence of a co-oxidant was not necessary. 

A.G.M. Barrett and co-workers reported the first total synthesis of (-)-preussomerin G. In the late stages of the synthesis, the introduction of the desired cyclohexenone moiety was achieved using the Saegusa oxidation. The ketone was first converted to the silyl enol ether with trimethylsilyl triflate, and then it was treated with stoichiometric amounts of Pd(OAc)2. 

The first case of a tetrahedral palladium(O) tetraolefin complex (more exactly, Pd(diolefin)2) has been isolated in the course of the Saegusa oxidation of a silyl enol ether, aimed at the synthesis of alkaloids. Palladium acetate was used as oxidant in this reaction, and a brown compound separated from the solution, which was characterized by X-ray diffraction as 16 (Equation (5)). It decomposed upon heating to give the expected product of oxidation. This supports the accepted mechanism of Saegusa oxidation. ... 

The total synthesis of (+/—)-stemonamide (37) (Scheme 20) proceeded from 212 via the Saegusa oxidation of the corresponding silyl enol ether to provide the... 

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