100-86-7Relevant articles and documents
Reactivity of a Palladacyclic Complex: A Monodentate Carbonate Complex and the Remarkable Selectivity and Mechanism of a Neophyl Rearrangement
Behnia, Ava,Fard, Mahmood A.,Blacquiere, Johanna M.,Puddephatt, Richard J.
, p. 4759 - 4769 (2017)
The ligand N(CH2-2-C5H4N)2(CH2CH2CH2OH), L1, reacted with [Pd(CH2CMe2C6H4)(COD)] to give a new fluxional cycloneophyl organopalladium complex [Pd(CH2CMe2C6H4)(κ2-L1)], 1, which on attempted recrystallization from THF gave the monodentate carbonate complex [Pd(CO3)(κ3-L1)], 2. Complex 2 was prepared in designed syntheses by reaction of [PdCl(κ3-L1)]+ with silver carbonate or by reaction of [Pd(OH)(κ3-L1)]+ with CO2. Complex 1 reacted with aqueous CO2 to give the cationic neophylpalladium complex [Pd(CH2CMe2C6H5)(κ3-L1)]+(HCO3)-, 6. Complex 6 reacts with hydrogen peroxide to give complex 2 with release of a mixture of organic products, the major one being 2-phenyl-2-butanol, PB. The formation of PB involves a neophyl rearrangement with the unprecedented preference for methyl over phenyl migration. A mechanistic basis for this unexpected reaction is proposed, involving β-carbon elimination at a palladium(IV) center.
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.
, p. 8303 - 8311 (2008)
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.
Catalytic Replacement of Unactivated Alkane Carbon-Hydrogen Bonds with Carbon-X Bonds (X = Nitrogen, Oxygen, Chlorine, Bromine, or Iodine). Coupling of Intermolecular Hydrocarbon Activation by MnIIITPPX Complexes with Phase-Transfer Catalysis
Hill, Craig L.,Smegal, John A.,Henly, Timothy J.
, p. 3277 - 3281 (1983)
A simple system has been devised to facilitate the first processes for the catalytic replacement of unactivated alkane C-H bonds with C-X bonds, X = nitrogen and iodine.The system also enables alkane C-H bonds to be replaced by C-X bonds, X = chlorine, bromine, and oxygen.The system is composed of two liquid phases and the oxidant iodosylbenzene (iodosobenzene).The alkane substrate, the MnIIITPPX catalyst, and the organic solvent (dichloromethane, chlorobenzene, or other aromatic hydrocarbon) constitute one phase, a saturated aqueous solution of the sodium salt of the anion to be incorporated into the alkane, NaX, X = N3(1-), NCO(1-), I(1-), Br(1-), or Cl(1-), constitutes the second phase, and the sparingly soluble oxidant iodosylbenzene constitutes a third phase.When the two liquid phases and the oxidant iodosylbenzene are stirred under an inert atmosphere, both RX and ROH products are produced catalytically based on MnTPP and in reasonable yield based on iodosylbenzene.The MnTPP moiety functions as a catalyst for C-H bond cleavage and for phase transfer of X(1-) from the aqueous phase to the organic phase where the functionalization chemistry takes place.The oxidant hypochlorite can be used in place of, but is less effective than, iodosylbenzene, and the oxidants hydrogen peroxide, periodate, and persulfate are ineffective.Product distributions obtained from the oxidation of cyclohexane, isobutane, 2,3-dimethylbutane, and tert-butylbenzene are most consistent with a product-determining step that involves transfer of X from manganese to a free alkyl radical intermediate.
Tuning the selectivity in the aerobic oxidation of cumene catalyzed by nitrogen-doped carbon nanotubes
Liao, Shixia,Chi, Yumei,Yu, Hao,Wang, Hongjuan,Peng, Feng
, p. 555 - 560 (2014)
In this study it is demonstrated that carbon nanotubes (CNTs) with doped nitrogen atoms in graphitic domains (NCNTs) can act as a new class of metal-free catalysts exhibiting excellent activity in the aerobic oxidation of cumene. We proved that NCNTs can promote the decomposition of hydroperoxide cumene with exceptionally high activity, resulting in strongly increased cumene conversion and extraordinarily high selectivity to acetophenone and 2-benzyl-2-propanol. The incorporation of nitrogen altered the surface electron structure of the CNTs and tuned the reactivity and selectivity. DFT calculations revealed that the remarkable improvement of catalytic performance of NCNTs is caused by the strong interaction between hydroperoxide cumene and the NCNTs. NCNTs also exhibited desirable recyclability after four cycling tests. This study not only provides a novel method for the cumene oxidation to high-value-added products at moderate reaction temperatures and oxygen atmospheric pressure, but also gives new insights into the effect of surface nitrogen doping on carbon-catalyzed liquid-phase oxidation of aromatic hydrocarbons. b Copyright
Use of Sacrificial Anodes in Electrochemical Functionalization of Organic Halides
Chaussard, Jacques,Folest, Jean-Claude,Nedelec, Jean-Yves,Perichon, Jacques,Sibille, Soline,Troupel, Michel
, p. 369 - 381 (1990)
This article reviews the new possibilities in organic synthesis offered by the electroreduction of organic halides in the presence of various electrophiles using sacrificial metallic anodes.
Mechanistic Insights into Fe Catalyzed α-C?H Oxidations of Tertiary Amines
Legacy, Christopher J.,Hope, Taylor O.,Gagné, Yohann,Greenaway, Frederick T.,Frenette, Mathieu,Emmert, Marion H.
, p. 235 - 246 (2021)
We report detailed mechanistic investigations of an iron-based catalyst system, which allows the α-C?H oxidation of a wide variety of amines. In contrast to other catalysts that effect α-C?H oxidations of tertiary amines, the system under investigation exclusively employs peroxy esters as oxidants. More common oxidants (e. g. tBuOOH) previously reported to affect amine oxidations via free radical pathways do not provide amine α-C?H oxidation products in combination with the described catalyst system. The investigations described herein employ initial rate kinetics, kinetic profiling, DFT calculations as well as Eyring, kinetic isotope effect, Hammett, ligand coordination, and EPR studies to shed light on the Fe catalyst system. The obtained data suggest that the catalytic mechanism proceeds through C?H abstraction at a coordinated substrate molecule. This rate-determining step occurs either through an Fe(IV) oxo pathway or a 2-electron pathway at an Fe(II) intermediate with bound oxidant. DFT calculations indicate that the Fe(IV) oxo mechanism will be the preferred route of these two possibilities. We further show via kinetic profiling and EPR studies that catalyst activation follows a radical pathway, which is initiated by hydrolysis of PhCO3tBu to tBuOOH. Overall, the obtained mechanistic data support a non-classical, Fe catalyzed pathway that requires substrate binding, inducing selectivity for α-C?H functionalization.
Model dialkyl peroxides of the fenton mechanistic probe 2-methyl-1-phenyl-2-propyl hydroperoxide (MPPH): Kinetic probes for dissociative electron transfer
Magri, David C.,Workentin, Mark S.
, p. 3418 - 3429 (2003)
Two dialkyl peroxides, devised as kinetic probes for the heterogeneous electron transfer (ET), are studied using heterogeneous and homogeneous electrochemical techniques. The peroxides react by concerted dissociative ET reduction of the O-O bond. Under heterogeneous conditions, the only products isolated are the corresponding alcohols from a two-electron reduction as has been observed with other dialkyl peroxides studied to date. However, under homogeneous conditions, a generated alkoxyl radical undergoes a rapid β-scission fragmentation in competition with the second ET resulting in formation of acetone and a benzyl radical. With knowledge of the rate constant for fragmentation and accounting for the diffuse double layer at the electrode interface, the heterogeneous ET rate constant to the alkoxyl radicals is estimated to be 1500 cm s-1. The heterogeneous and homogeneous ET kinetics of the O-O bond cleavage have also been measured and examined as a function of the driving force for ET, ΔGET, using dissociative electron transfer theory. From both sets of kinetics, besides the evaluation of thermochemical parameters, it is demonstrated that the heterogeneous and homogeneous reduction of the O-O bond appears to be non-adiabatic.
Visible-Light-Driven Palladium-Catalyzed Radical Alkylation of C?H Bonds with Unactivated Alkyl Bromides
Zhou, Wen-Jun,Cao, Guang-Mei,Shen, Guo,Zhu, Xing-Yong,Gui, Yong-Yuan,Ye, Jian-Heng,Sun, Liang,Liao, Li-Li,Li, Jing,Yu, Da-Gang
, p. 15683 - 15687 (2017)
Reported herein is a novel visible-light photoredox system with Pd(PPh3)4 as the sole catalyst for the realization of the first direct cross-coupling of C(sp3)?H bonds in N-aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra- and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp3)?C(sp3) and C(sp2)?C(sp3) bonds in moderate to excellent yields. These redox-neutral reactions feature broad substrate scope (>60 examples), good functional-group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible-light photocatalyst and radicals are involved in the process.
Hydrocarbon Functionalization by the (Iodosylbenzene)manganese(IV) Porphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Oxidation System. Mechanism and Reaction Chemistry
Smegal, John A.,Hill, Craig L.
, p. 3515 - 3521 (1983)
The two types of complexes isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene - IVTPP(OIPh)>2O, 1, X = Cl- or Br-, and IVTPP>2O, 2, X = N3- - are capable of oxidizing alkane substrates in good yields at room temperature.Several lines of evidence establish the intermediacy of free alkyl radicals in the reactions of 1 and 2 with alkanes.Oxygen exchange with water in both the iodosyl (Mn-O-I) and μ-oxo (Mn-O-Mn) moieties of 1 suggests the formation of oxo manganese porphyrin complexes from these moieties.Hydrogen abstraction from the alkane substrate by an oxo manganese porphyrin intermediate is postulated to be mechanism for reaction of 1 and 2 with alkanes.Observation of a monomeric manganese(IV) porphyrin intermediate by EPR spectroscopy during the reactions of 1 with alkanes is consistent with the formation of a hydroxymanganese(IV) porphyrin complex resulting from substrate hydrogen abstraction by an oxo intermediate.The formation of RX product from oxidation of RH by 1 has been determined to result from ligand-transfer oxidation of free alkyl radicals by the porphyrin complexes in solution.Through competition reactions and time-dependent product formation studies, ligand-transfer oxidation by XMnIIITPP was found to be the major pathway for RX production.Observation of MnIITPP by EPR spectroscopy during the reactions of 1 with alkanes supports this conclusion.Formation of ROH product may result from ligand-transfer oxidation of free radicals or from the collapse of an intermediate caged radical pair.The mechanism of ROH product formation in the caged radical pair is postulated to be an outer-sphere electron-transfer process due to the expected slow rate of inner-sphere ligand transfer for the high-spin d3 hydroxymanganese(IV) porphyrin complex.Thus the ability of the substrate radical to undergo electron-transfer oxidation determines the ratio of radicals that undergo cage escape to give free radicals to radicals that undergo oxidation and subsequent formation of alcohol product in the caged species.Studies with tertiary substrates support these conclusions.
Highly powerful and practical acylation of alcohols with acid anhydride catalyzed by Bi(OTf)3
Orita,Tanahashi,Kakuda,Otera
, p. 8926 - 8934 (2001)
Bi(OTf)3-catalyzed acylation of alcohols with acid anhydride was evaluated in comparison with other acylation methods. The Bi(OTf)3/acid anhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed in order to overcome difficulty in separation of the acylated product from the remaining acylating reagent: methanolysis of the unreacted anhydride into easily separable methyl ester realized quite easy separation of the desired acylation product. The Bi(OTf)3/acid anhydride protocol was applicable to a wide spectrum of alcohols bearing various functionalities. Acid-labile THP- or TBS-protected alcohol, furfuryl alcohol, and geraniol could be acylated as well as base-labile alcohols. Even acylation of functionalized tertiary alcohols was effected at room temperature.
