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The Saegusa–Ito oxidation is a chemical reaction used in organic chemistry. It was discovered in 1978 by Takeo Saegusa and Yoshihiko Ito as a method to introduce α-β unsaturation in carbonyl compounds. The reaction as originally reported involved formation of a silyl enol ether followed by treatment with palladium(II) acetate and benzoquinone to yield the corresponding enone. The original publication noted its utility for regeneration of unsaturation following 1,4-addition with nucleophiles such as organocuprates. For acyclic substrates the reaction yields the thermodynamic E-olefin product exclusively. This discovery was preceded nearly eight years earlier by a report that treatment of unactivated ketones with palladium acetate yielded the same products in low yields. The major improvement provided by Saegusa and Ito was the recognition that the enol form was the reactive species, developing a method based on silyl enol ethers. Benzoquinone is actually not a necessary component for this reaction; its role is to regenerate palladium(II) from its reduced form palladium(0), so that a smaller amount of expensive palladium(II) acetate is required at the beginning. The reaction conditions and purifications could be easily simplified by just using excess of palladium(II) acetate without benzoquinone, while at a much higher cost. Since the reaction typically employs near-stoichiometric amounts of palladium and is therefore often considered too expensive for industrial usage, some progress has been made in the development of catalytic variants. Despite this shortcoming, the Saegusa oxidation has been used in a number of syntheses as a mild, late-stage method for introduction of functionality in complex molecules. ==Mechanism== The mechanism of the Saegusa–Ito oxidation involves coordination of palladium to the enol olefin followed by loss of the silyl group and formation of an oxoallyl-palladium complex. β-hydride elimination yields the palladium hydride enone complex which upon reductive elimination yields the product along with acetic acid and Pd0.〔(Oxidation ), Chem 215 lecture notes〕 The reversibility of the elimination step allows equilibration, leading to the thermodynamic E-selectivity in acyclic substrates. It has been shown that the product can form a stable Pd0-olefin complex, which may be responsible for the difficulty with re-oxidation seen in catalytic variants of the reaction. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Saegusa–Ito oxidation」の詳細全文を読む スポンサード リンク
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