75714-97-5Relevant academic research and scientific papers
On the Mechanism of Oxygenation of Olefins by Tetraphenylporphinatoiron(III)-Peroxide Systems
Muto, Toshiki,Masumori, Hiroaki,Miura, Toshiaki,Kimura, Michiya
, p. 2177 - 2183 (2007/10/02)
The mode of oxygenation by meso-tetraphenylporphinatoiron(III)-chloride (Fe(III)TPPCl)-peroxide systems was characterized by using cis-stilbene (1) and cholesteryl acetate (3) as substrates.The stereoselectivity of epoxidation of 1 by the Fe(III)TPPCl-tert-butyl hydroperoxide (tBuOOH) system depended on the concentration of Fe(III)TPPCl; the reaction was nonstereoselective at 0.1 mM Fe(III)TPPCl but stereoselective at 10 mM Fe(III)TPPCl.In the reaction of 3 with the same system, both allylic oxidation and epoxidation proceeded.However, the epoxidation was β-selective independently of the concentration of Fe(III)TPPCl.Thus, tBuOOH is assumed to decompose by a radical chain reaction mechanism to give tert-butylperoxyl radical (tBuOO.) and tert-butyloxyl radical (tBuO.) at 0.1 mM Fe(III)TPPCl.At 10 mM Fe(III)TPPCl, on the other hand, the O-O bond in the Fe(III)TPPCl-tBuOOH complex may cleave in both a homolytic manner (quasi-Fenton mechanism) and a heterolytic one (ferryl ion mechanism).The former leads to tBuO. as the active oxygen species responsible for the allylic oxidation of 3 and the latter to ferryl ion (Fe-O.) as that responsible for the stereoselective epoxidation of 1 and β-epoxidation of 3.In the reaction with the Fe(III)TPPCl-m-chloroperbenzoic acid (MCPBA) system at -30 deg C in the presence of γ-collidine, β-selective epoxidation of 3 proceeded predominantly while 1 was epoxidized stereoselectively.The stereoselectivities of these epoxidations closely resemble those with the Fe(III)TPPCl-iodosylbenzene system, which is known to give the ferryl ion.These results suggest that the O-O bond in the Fe(III)TPPCl-MCPBA complex cleaves mainly in the heterolytic manner (ferryl ion mechanism).Keywords---epoxidation stereoselectivity; cholesteryl acetate; cis-stilbene;
On the Mode of Oxygenation with the Ferric Perchlorate-Hydrogen Peroxide System
Muto, Toshiki,Urano, Chizuko,Hayashi, Toru,Miura, Toshiaki,Kimura, Michiya
, p. 1166 - 1171 (2007/10/02)
The reactions of three kinds of substrates with hydrogen peroxide catalyzed by ferric perchlorate in acetonitrile were investigated and compared with those occurring in the Fe(acac)3/alkylhydroperoxide system, which are governed by a radical process.Allylic oxidation and epoxidation both proceeded in the reaction of cholesteryl acetate, and the α-stereoselectivity of the epoxidation was enhanced by the presence of a radical scavenger.In the reactions of cis- and trans-stilbenes, stereospecific epoxidation by a non-radical process occurred, as well as a non-stereospecific reaction.The third substrate, adamantane, was shown to undergo more extensive oxygenation at its secondary carbon atoms than it did in the autooxidation and the Fe(acac)3/ROOH systems.Thus, it was concluded that the reaction in the Fe(ClO4)3/H2O2/CH3CN system involves both radical and non-radical processes. Keywords---ferric perchlorate; hydrogen peroxide; cholesteryl acetate; stilbene; adamantane; α-epoxidation of cholesteryl acetate; stereospecific epoxidation of stilbene; oxygenation of adamantane; non radical process; radical process
THE REACTIONS OF CHOLESTERYL ACETATE WITH VARIOUS HYDROPEROXIDES IN THE PRESENCE OF TRIS(ACETYLACETONATO)IRON (III) AND HEXACARBONYLMOLYBDENUM
Kimura, Michiya,Muto, Toshiki
, p. 1836 - 1841 (2007/10/02)
Epoxidation and allylic oxidation of cholesteryl acetate were studied using hydroperoxide (ROOH: R = H, ethyl, iso-propyl, tert-butyl, or cumyl) and a metal complex in benzene or acetonitrile.In the presence of the iron catalyst, formation of the epimeric C(5,6)-epoxides predominated in the reactions with H2O2, while allylic oxidation giving C(7)-ketone, epimeric C(7)-alcohols and C(7)-alkyl peroxides was favored in the reactions with alkyl hydroperoxide, regardless of the polarity of the solvent.The stereoselective β-epoxidation was independent of the structure of ROOH, but the ratio of allylic oxidation to epoxidation was dependent on it.When the iron catalyst was replaced by the molybdenum catalyst, β-epoxidation decreased and solvent effects on the reaction were sufficiently mareked to exclude allylic oxidation in the non-polar medium. - Keywords - alkyl-hydroperoxide; allylic oxidation; cholesterol; epoxide; ferric acetylacetonate; hydrogen peroxide; molybdenum hexacarbonyl; solvent effects; stereoselective epoxidation
