Oxidation, Saegusa

Palladium-catalyzed conversion of enol silanes to enones, also known as the Saegusa enone synthesis. 

The mechanism is similar to that of the Wacker oxidation (page 610). 

Larock reported regeneration of the Pd(II) oxidant using oxygen Pd(0) + O2 ------------------- 

Trauner, D. Giester, G. Mulzer, J. Angew. Chem., Int. Ed. 1999, 38, 2015. The authors proposed sandwiched Pd(ll) as a possible alternative pathway. 

Larock reported regeneration of die Pd(II) oxidant using oxygen  

Name Reactions, 4th ed., DOI 10.1007/978-3-642-01053-8 225, Springer-Verlag Berlin Heidelberg 2009 

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, DOI 10.1007/978-3-319-03979-4 240, Springer International Publishing Switzerland 2014 

Saegusa, T. J. Org. Chem. 1978, 43, 1011-1013. Takeo Saegusa was a professor at Kyoto University in Japan. 

When substoichiometric/stoichiometric amounts of PdfOAc), is used  

When the oxidation takes place under an oxygen atmosphere with catalytic amounts of Pd(OAc)2  

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. 

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 Larock modified Saegusa oxidation conditions were utilized in the total synthesis of ( )-8,14-cedranoxide by M. lhara et al. The main strategy was to apply an intramolecular double Michael addition reaction to assemble the tricyclic cedranoid skeleton. The precursor five-membered enone was prepared in high yield from the corresponding substituted cyclopentanone in two steps. 

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SAE reaction see Sharpless asymmetric epoxidation Saegusa oxidation 390 samarium diiodide 496, 633, 638 saponification 49, 207 sativene 382 f. 

Ketone rac-13 was transformed into the corresponding silylenolether and by Pd(II)-mediated Saegusa oxidation [14] into a, -unsaturated ketone rac-14. By alkylative enone transposition comprising methyl lithium addition and pyridinium chlorochromate (PCC) oxidation [15], rac-14 was finally converted into the racemic photo cycloaddition precursor rac-6. In conclusion, the bicyclic irradiation precursor rac-6 was synthesized in a straightforward manner from simple 1,5-cyclooctadiene (11) in nine steps and with an overall yield of 21%. 

When applicable, there is selectivity for ( -products Saegusa Oxidation... 

Saegusa oxidation Regioselective introduction of the carbon-carbon doubie bond to cyciic and acyiic ketones yia Pd-mediated oxidation of the corresponding siiyi enol ethers. 390... 

Other references related to the Saegusa oxidation are cited in the literature. ... 

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