1944-83-8Relevant articles and documents
DECOMPOSITION OF ORGANIC PEROXIDES AND HYDROGEN PEROXIDE BY THE IRON THIOLATES AND RELATED COMPLEXES
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Paragraph 0725; 0754-0755, (2020/07/04)
Disclosed herein is a method of reducing or disproportionating peroxide, comprising combining an organic chalcogenide, an iron salt, and the peroxide in the presence of an additional reductant, which can be the organic chalcogenide. The method can be used to, e.g., prepare alcohols from peroxides and to disproportionate hydrogen peroxide into water and oxygen.
Tuning the Diiron Core Geometry in Carboxylate-Bridged Macrocyclic Model Complexes Affects Their Redox Properties and Supports Oxidation Chemistry
Wang, Fang,Becker, Sabine,Minier, Mikael A.,Loas, Andrei,Jackson, Megan N.,Lippard, Stephen J.
supporting information, p. 11050 - 11058 (2017/09/26)
We introduce a novel platform to mimic the coordination environment of carboxylate-bridged diiron proteins by tethering a small, dangling internal carboxylate, (CH2)nCOOH, to phenol-imine macrocyclic ligands (H3PIMICn). In the presence of an external bulky carboxylic acid (RCO2H), the ligands react with [Fe2(Mes)4] (Mes = 2,4,6-trimethylphenyl) to afford dinuclear [Fe2(PIMICn)(RCO2)(MeCN)] (n = 4-6) complexes. X-ray diffraction studies revealed structural similarities between these complexes and the reduced diiron active sites of proteins such as Class I ribonucleotide reductase (RNR) R2 and soluble methane monooxygenase hydroxylase. The number of CH2 units of the internal carboxylate arm controls the diiron core geometry, affecting in turn the anodic peak potential of the complexes. As functional synthetic models, these complexes facilitate the oxidation of C-H bonds in the presence of peroxides and oxo transfer from O2 to an internal phosphine moiety.
Synthesis of Ethers via Reaction of Carbanions and Monoperoxyacetals
Kyasa, ShivaKumar,Meier, Rebecca N.,Pardini, Ruth A.,Truttmann, Tristan K.,Kuwata, Keith T.,Dussault, Patrick H.
, p. 12100 - 12114 (2016/01/09)
Although transfer of electrophilic alkoxyl ("RO+") from organic peroxides to organometallics offers a complement to traditional methods for etherification, application has been limited by constraints associated with peroxide reactivity and stability. We now demonstrate that readily prepared tetrahydropyranyl monoperoxyacetals react with sp3 and sp2 organolithium and organomagnesium reagents to furnish moderate to high yields of ethers. The method is successfully applied to the synthesis of alkyl, alkenyl, aryl, heteroaryl, and cyclopropyl ethers, mixed O,O-acetals, and S,S,O-orthoesters. In contrast to reactions of dialkyl and alkyl/silyl peroxides, the displacements of monoperoxyacetals provide no evidence for alkoxy radical intermediates. At the same time, the high yields observed for transfer of primary, secondary, or tertiary alkoxides, the latter involving attack on neopentyl oxygen, are inconsistent with an SN2 mechanism. Theoretical studies suggest a mechanism involving Lewis acid promoted insertion of organometallics into the O-O bond.
Catalysis and molecular magnetism of dinuclear iron(iii) complexes with N-(2-pyridylmethyl)-iminodiethanol/-ate
Shin, Jong Won,Bae, Jeong Mi,Kim, Cheal,Min, Kil Sik
, p. 3999 - 4008 (2014/03/21)
The reaction of N-(2-pyridylmethyl)iminodiethanol (H2pmide) and Fe(NO3)3·9H2O in MeOH led to the formation of a dimeric iron(iii) complex, [(Hpmide)Fe(NO3)] 2(NO3)2·2CH3OH (1). Its anion-exchanged form, [(pmide)Fe(N3)]2 (2), was prepared by the reaction of 1 and NaN3 in MeOH, during which the Hpmide ligand of 1 was also deprotonated. These compounds were investigated by single crystal X-ray diffraction and magnetochemistry. In complex 1, one iron(iii) ion was bonded with a mono-deprotonated Hpmide ligand and a nitrate ion. The two iron(iii) ions within the dinuclear unit were connected by two ethoxy groups with an inversion center. In 2, one iron(iii) ion was coordinated with a deprotonated pmide ligand and an azide ion. The Fe(pmide)(N3) unit was related by symmetry through an inversion center. Both 1 and 2 efficiently catalyzed the oxidation of a variety of alcohols under mild conditions. The oxidation mechanism was proposed to involve an FeIVO intermediate as the major reactive species and an FeVO intermediate as a minor oxidant. Evidence for this proposal was derived from reactivity and Hammett studies, KIE (kH/kD) values, and the use of MPPH (2-methyl-1-phenylprop-2-yl hydroperoxide) as a mechanistic probe. Both compounds had significant antiferromagnetic interactions between the iron(iii) ions via the oxygen atoms. 1 showed a strong antiferromagnetic interaction within the Fe(iii) dimer, while 2 had a weak antiferromagnetic coupling within the Fe(iii) dimer.
Cobalt-salen complex-catalyzed oxidative generation of alkyl radicals from aldehydes for the preparation of hydroperoxides
Watanabe, Eiichi,Kaiho, Atsushi,Kusama, Hiroyuki,Iwasawa, Nobuharu
supporting information, p. 11744 - 11747 (2013/09/02)
Catalytic generation of alkyl radicals from aldehydes via oxidative deformylation was realized using a cobalt-salen complex with H2O 2. The deformylation was thought to proceed through homolytic cleavage of peroxohemiacetal intermediates to provide even primary alkyl radicals under mild conditions. Variously substituted and functionalized hydroperoxides were obtained from corresponding aldehydes in good yield.
Heterolytic cleavage of peroxide by a diferrous compound generates metal-based intermediates identical to those observed with reactions utilizing oxygen-atom-donor molecules
Rowe, Gerard T.,Rybak-Akimova, Elena V.,Caradonna, John P.
experimental part, p. 8303 - 8311 (2009/12/02)
Under cryogenic stoppedflow conditions, addition of 2-methyl-lphenylprop-2- yl hydroperoxide (MPPH) to the diiron(II) compound, [Fe2(H 2Hbamb)2(NMeIm)2] (1; NMeIm = /V-methylimidazole; H4HBamb: 2,3-bis(2-hydroxybenzamido) dimethylbutane) results in heterolytic peroxide ○-○ bond cleavage, forming a highvalent species, 2. The UV/Vis spectrum of 2 and its kinetic behavior suggest parallel reactivity to that seen in the reaction of 1 with oxygen-atom-donor (OAD) molecules, which has been reported previously. Like the interaction with OAD molecules, the reaction of 1 with MPPH proceeds through a three step process, assigned to oxygen-atom transfer to the iron center to form a high-valent intermediate (2), ligand rearrangement of the metal complex, and, finally, decay to a diferric μ-oxo compound. Careful examination of the order of the reaction with MPPH reveals saturation behavior. This, coupled with the anomalous non-Arrhenius behavior of the first step of the reaction, indicates that there is a preequilibrium peroxide binding step prior to ○-○ bond cleavage. At higher temperatures, the addition of the base, proton sponge, results in a marked decrease in the rate of ○-○ bond cleavage to form 2; this is assigned as a peroxide deprotonation effect, indicating that the presence of protons is an important factor in the heterolytic cleavage of peroxide. This phenomenon has been observed in other iron-containing enzymes, the catalytic cycles of which include peroxide O-O bond cleavage.
Synthesis of cyclic peroxides by chemo- and regioselective peroxidation of dienes with Co(II)/O2/Et3SiH
Tokuyasu, Takahiro,Kunikawa, Shigeki,McCullough, Kevin J.,Masuyama, Araki,Nojima, Masatomo
, p. 251 - 260 (2007/10/03)
(Chemical Equation Presented). In the competitive peroxidation of mixtures of two alkenes with Co(II)/O2/Et3SiH, it was found that the relative reactivities of the alkene substrates are influenced by three major factors:. (1) relative stability of the intermediate carbon-centered radical formed by the reaction of the alkene with HCo(III) complex, (2) steric effects around the C=C double bond, and (3) electronic factors associated with the C=C double bond. Consistent with results from simple alkenes, the chemo-and regioselective peroxidation of dienes was also realized. Depending on the diene structure, the product included not only the expected acyclic unsaturated triethylsilyl peroxides but also 1,2-dioxolane and 1,2-dioxane derivatives via intramolecular cyclization of the unsaturated peroxy radical intermediates.
Fe2+-catalyzed heterolytic RO-OH bond cleavage and substrate oxidation: A functional synthetic non-heme iron monooxygenase system
Foster, Trina L.,Caradonna, John P.
, p. 3678 - 3679 (2007/10/03)
The reaction of [Fe22+(H2Hbamb)2(N-MeIm)2], [1], a binuclear, non-heme iron complex, with 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) shows that [1] induces heterolytic cleavage of the peroxy O-O
Syntheses, structures, and reactivities of Cobalt(III)-alkylperoxo complexes and their role in stoichiometric and catalytic oxidation of hydrocarbons
Chavez, Ferman A.,Rowland, John M.,Olmstead, Marilyn M.,Mascharak, Pradip K.
, p. 9015 - 9027 (2007/10/03)
Although Co(III)-alkyl peroxo species have often been implicated as intermediates in industrial oxidation of hydrocarbons with cobalt catalysts, examples of discrete [LCo(III)-OOR] complexes and studies on their oxidizing capacities have been scarce. In this work, twelve such complexes with two different ligands, L, and various primary, secondary, and tertiary R groups have been synthesized, and seven of them have been characterized by X-ray crystallography. The dianion (L2-) of the two ligands N,N-bis[2-(2- pyridyl)ethyl]-pyridine-2,6-dicarboxamide (Py3PH2, 1) and N-N-bis[2-(1- pyrazolyl)ethyl]pyridine-2,6-dicarboxamide (PyPz2-PH2, 2) bind Co(III) centers in pentadentate fashion with two deprotonated carboxamido nitrogens in addition to three pyridine or one pyridine and two pyrazole nitrogens to afford complexes of the type [LCo(III)(H2O)] and [LCo(III)(OH)]. Reactions of the [LCo(III)(OH)] complexes with ROOH in aprotic solvents of low polarity readily afford the [LCo(III)-OOR] complexes in high yields. This report includes syntheses of [Co(Py3P)(OOR)] complexes with R = (t)Bu (7, (t)Bu) = CMe3), Cm (8, Cm = CMe2Ph), CMe2CH2Ph (9), Cy (10, Cy = c-C6H11), (i)Pr (11, (i)Pr = CHMe2) or (n)Pr (12, (n)Pr = CH2CH2CH3), and [Co(PyPz2P)(OOR) complexes with R = (t)Bu (13), Cm (14), CMe2CH2Ph (15), Cy (16), (i)Pr (17) or (n)Pr (18). The structures of 8-12 and 16 have been established by X-ray crystallography. Complexes 10 and 16 are the first examples of structurally characterized compounds containing the [Co-OOCy] unit, proposed as a key intermediate in cobalt-catalyzed oxidation of cyclohexane. The metric parameters of 7-12 and 16 have been compared with those of other reported [LCo(III)-OOR] complexes. When these [LCo(III)-OOR] complexes are warmed (60-80 °C) in dichloromethane in the presence of cyclohexane (CyH), cyclohexanol (CyOH) and cyclohexanone (CyO) are obtained in good yields. Studies on such reactions (referred to as stoichiometric oxidations) indicate that homolysis of the O-O bond in the [LCo(III)-OOR] complexes generates RO· radicals, in the reaction mixtures which are the actual agents for alkane oxidation. [LCo-O·], the other product of homolysis, does not promote any oxidation. A mechanism for alkane oxidation by [LCo(III)-OOR] complexes has been proposed on the basis of the kinetic isotope effect (KIE) value (5 at 80 °C), the requirement of dioxygen for oxidation, the dependence of yields on the stability of the RO· radicals, and the distribution of products with different substrates. Both L and R modulate the capacity for alkane oxidation of the [LCo(III)-OOR] complexes. The extent of oxidation is noticeably higher in solvents of low polarity, while the presence of water invariably lowers the yields of the oxidized products. Since [LCo(III)-OOR] complexes are converted into the [LCo(III)(OH)] complexes at the end of single turnover in stoichiometric oxidation reactions, it is possible to convert these systems into catalytic ones by the addition of excess ROOH to the reaction mixtures. The catalytic oxidation reactions proceed at respectable speed at moderate temperatures and involve [LCo(III)-OOR] species as a key intermediate. Turnover numbers over 100 and ~10% conversion of CyH to CyOH and CyO within 4 h have been noted in most catalytic oxidations. The same catalyst can be used for the oxidation of many substrates. The results of the present work indicate that [LCo(III)- OOR] complexes can promote oxidation of hydrocarbons under mild conditions and are viable intermediates in the catalytic oxidation of hydrocarbons with ROOH in the presence of cobalt catalysts.
Homolytic Decomposition of t-Alkyl 2,2-Dimethylperoxypropionates
Komai, Takeshi,Matsuyama, Kazuo,Matsushima, Masaru
, p. 1641 - 1646 (2007/10/02)
Decomposition rates and products of t-alkyl 2,2-dimethylperoxypropionates were measured in cumene at several temperatures.The peroxyesters decomposed homolitycally, depending on the structure of the t-alkyl moiety.The relative rates of the t-alkyl moieties to the 1,1-dimethylethyl one were: 1,1-dimethylbutyl (1.14), 1,1-dimethylpropyl (1.19), 1,1,2-trimethylpropyl (1.85), 1,1,3,3-tetramethylbutyl (2.10), and 1,1-dimethyl-2-phenylethyl (2.34).The decomposition showed an isokinetic relationship and the importance of stabilization by hyperconjugation.Based on these data, the decomposition mechanism, which contains a slight stretching of the Cα-Cβ bond to the peroxyl oxygen at the transition state is, discussed.
