- Decarbonylation of Adamantan-2-one by Two-photonic Excitation with XeCl Laser
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Adamantan-2-one 1 in cyclohexane undergoes decarbonylation to give noradamantane 2 via two-photon absorption of XeCl laser light (308 nm).
- Ichinose, Nobuyuki,Kawanishi, Shunichi
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- 4-Azahomoadamant-3-ene: Spectroscopic Characterization and Photoresolution of a Highly Reactive Strained Bridgehead Imine
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Low-temperature irradiation of 1-azidoadamantane in argon, nitrogen, 3-methylpentane, or polyethylene matrices or as neat solid produced (i) the diamagnetic highly reactive strained bridgehead imine, 4-azahomoadamant-3-ene, characterized by its vibrational (Raman, IR) and electronic (UV absorption, CD) spectra, (ii) traces of 1-adamantylnitrene, detected by EPR spectroscopy and by photochemical trapping with CO, and (iii) molecular nitrogen, detected by Raman spectroscopy.A warm-up in any of the matrices produced the known dimer of the imine.In an argon matrix or in the neat solid, dimerization was observed to proceed rapidly already at about 60 K.Optical resolution of the bridgehead imine to 2percent optical purity was achieved by irradiation with circularly polarized 308-nm laser light, preferably in polyethylene between 160 and 200 K where rotational diffusion of the imine is fast and translational diffusion still slow.The activation energy for thermal racemization is believed to be at least 17 kcal/mol since no racemization was detected up to 220 K, at which temperature dimerization in the polyethylene matrix begins to be significant.Interpretation of the results is based on calculations by MNDO and INDO/S methods and suggests that the torsion angle of the severely distorted C=N moiety is 50 +/- 10 deg.
- Radziszewski, Juliusz G.,Downing, John W.,Jawdosiuk, Mikolaj,Kovacic, Peter,Michl, Josef
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- Oxidation of Adamantane with H2O2–CF3COCF3 · 1.5 H2O in the Presence of VO(acac)2
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The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)2 to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.
- Kislitsina,Shchadneva,Khusnutdinov
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- FURTHER STUDIES ON THE ACTIVATION OF THE C-H BOND IN SATURATED HYDROCARBONS
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Various saturated aliphatic and alicyclic hydrocarbons have been regioselectively oxidised with surprising efficiency by a system containing iron powder and a carboxylic acid in aqueous pyridine under an atmosphere of oxygen.A trace of hydrogen sulphide initiates the reaction.
- Barton, Derek H.R.,Hay-Motherwell, Robyn S.,Motherwell, William B.
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- Definitive Identification of the C-5 and C-7 NMR Signals of Adamantan-2-ol
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The E- and Z-5-deuterioadamantan-2-ols have been synthesized by an unambiguous route.The 13C NMR spectra show the familiar 1:1:1 splitting of one of the C-5 or C-7 signals, thus allowing a definite assignment of the δ-atoms to be made.This assignment is in accord with the conclusion of Duddeck and Islam.Revised assignments are offered for the reported configurations of the 5-bromo- and -chloro-adamantan-2-ols, and several unusual deuterium isotope shifts are reported.
- Srivastava, S.,Cheung, C. K.,Noble, W. J. de
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- Oxygenation of Alkanes by Molecular Oxygen on >10- Heteropolyanion
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Adamantane, ethylbenzene, and cyclohexane are catalytically and selectively oxidized to the corresponding alcohols and ketones with molecular oxygen alone on PW9-Fe2Ni heteropolyanion.
- Mizuno, Noritaka,Tateishi, Masaki,Hirose, To-oru,Iwamoto, Masakazu
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- Heterogeneously catalyzed liquid-phase oxidation of alkanes and alcohols with molecular oxygen
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RuCl3 successfully reacts with the lacunary silicotungustate in organic medium, giving a Ru3+-substituted silicotungstate that can act as a heterogeneous catalyst for the oxidation of a wide range of alkanes and alcohols using 1 atm of molecular oxygen as the sole oxidant.
- Yamaguchi, Kazuya,Mizuno, Noritaka
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- Hydroxylation of alkanes by molecular oxygen with dinuclear FeII macrocyclic complexes as catalysts
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The iron(II) complexes of two new macrocyclic ligands: [24]RBPyBC (L24), a 24-membered macrocycle containing phenol, pyridine and amino donor groups, and [30]RBBPyBC (L30), a 30-membered macrocycle containing phenol, bipyridine, and amino donor groups, were found to be effective for the hydroxylation of alkanes, including cyclohexane and adamantane, with H2S as a two-electron reductant.
- Wang, Zheng,Martell, Arthur E.,Motekaitis
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- A Maximum in a Grunwald-Winstein Plot for a Limiting SN1 Solvolysis
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The Grunwald-Winstein Y values for acetone-methanol mixtures vary appreciably and in a uniform manner but the specific rates of solvolysis of 2-adamantyl perchlorate vary by less than threefold over a range of from 5 to 100percent methanol content and a shallow maximum is observed.
- Kevill, Dennis N.,Bahari, Mohd S.
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- Epoxidation and hydroxylation reactions catalysed by β-Tetrahalogeno and β-octahalogeno manganese porphyrins
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β-Tetrahalogenated manganese(III) porphyrins are more efficient catalysts than the β-octahalogenated ones in oxidations promoted by H2O2.
- Baciocchi, Enrico,Boschi, Tristano,Cassioli, Luigi,Galli, Carlo,Lapi, Andrea,Tagliatesta, Pietro
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- Syntheses and characterization of chloro(Me2SO)ruthenium(II) complexes with tris(2-pyridylmethyl)amine or N,N-bis(2-pyridylmethyl)glycinate and their application for catalytic hydroxylation of alkane
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The new ruthenium(II) complexes, [RuCl(Me2SO)(TPA)]X (X = Cl or PF6) and [Ru(BPG)Cl(Me2SO)] were prepared, and the catalytic activity for alkane hydroxylation using m-chloroperbenzoic acid was examined.2 Two geometrical isomers of the TPA complexes were isolated and showed marked difference in activity: the trans(Cl, Namino) isomer is the most active and selective catalyst toward the oxygenation of adamantane giving 1-adamantanol (75%) and 2-adamantanol (5%).
- Yamaguchi, Motowo,Kousaka, Hiroyuki,Yamagishi, Takamichi
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- Activation of the C-H Bond in Hydrocarbons: the Isolation and Catalytic Activity of a Trinuclear Organoiron Carboxylate Cluster
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Tri-iron cluster compounds of type (1), in the presence of zinc powder, acetic acid, (aqueous) pyridine, and oxygen constitute an efficient and selective system for the oxidation of saturated hydrocarbons.
- Barton, Derek H. R.,Gastiger, Michel J.,Motherwell, William B.
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- Catalytic Homogeneous Functionalization of Adamantane. Influence of Electronic and Structural Features of the Metalloporphyrin Catalyst on Atom Transfer Selectivity (Oxygenation versus Azidification/Halogenation)
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Upon treatment of the two-phase systems, Mn tetraarylporphyrin, and alkane (organic phase)/Na+X- (aqueous phase), with iodosylarenes, both alcohols and alkyl azides (or halides), X- = halide or azide, are formed from the alkane substrates.The Mn porphyrin functions as a catalyst for alkane oxygenation and a phase transfer catalyst for X-.Catalytic functionalization of the exemplary caged alkane, adamantane, by a variety of these two-phase systems as function of the reaction conditions has been examined.The results reported here allow, for the first time, an assessment of the relathionship between the electronic and structural features of the metalloporphyrin catalysts and their selectivity with respect to the replacement of unactivated alkane carbon-hydrogen bonds with oxygen versus non-oxygen (halide or azide) functional groups.Of the first-row transition metal matalloporphyrins, only those of manganese are active for both the cleavage of unactivated alkane C-H bonds and replacement of these bonds by halogen or nitrogen-based groups.The oxygen donors that give the highest yields of these non-oxygenated products are the iodosylarenes.Examination of adamantane functionalization by iodosylarenes catalyzed by eight different manganese tetraphenylporphyrin derivatives, whose porphyrin ligands vary widely in electron-donating ability, establishes that the relative tertiary-secondary C-H cleavage selectivities are minimally affected by such electronic effects.In contrast, the selectivity for incorporation of the non-oxygen versus oxygen functions is substantially affected by the electron-donating ability of the catalyst porphyrin rings.The more electron withdrawing the porphyrin ring, and consequently the more anodic the potential of the ligated, S = 2, manganese(III) ion, the lower the selectivity for incorporation of the non-oxygen functions.Functionalization of adamantane catalyzed by the most electron poor manganese porphyrin complex, MnIII(F20TPP)X, is effectively selective for oxygenation.All the metalloporphyrins examined here eventually succumb to deactivation by irreversible oxidative degradation of the organic porphyrin ligand.
- Brown, Robert B.,Hill, Craig L.
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- A New Procedure for the Oxidation of Saturated Hydrocarbons
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The oxidation of adamantane can be achieved with unusual efficiency using molecular oxygen and a system comprising hydrogen sulphide and iron powder in pyridine containing acetic acid and a little water.
- Barton, Derek H. R.,Gastiger, Michel J.,Motherwell, William B.
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- Solvolysis of 2-adamantyl p-toluenesulfonate in ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate
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The solvolytic rate constants of 2-adamantyl p-toluenesulfonate were determined in [BMIM][BF4] in the presence/absence of 2,6-lutidine by NMR measurements. The activation parameters suggest that the reaction proceeded by kc mechanism. The solvolysis quantitatively gave 2-adamantanol as a product by the reaction with the water present in the ionic liquid. The solvent ionizing power of [BMIM][BF4] was found to be similar to that of ethanol.
- Okazaki, Takao,Ito, Koji,Kitagawa, Toshikazu
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- THE OXIDATION OF ADAMANTANE WITH AN IRON SALEN COMPLEX MODELLING ω-HYDROXYLASE
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An interesting regioseletivity (high secondary selectivity) was observed in the oxidation of adamantane in the presence of (FeSalen)2O, 2-mercaptoethanol, pyridine, and oxygen, giving 1-adamantanol (67 percent based on the catalyst used), 2-adamantanol (162 percent) and 2-adamantanone (51 percent) for a typical example.The yield of each product was dependent on the reaction conditions especially on the mercaptan concentration.This high secondary selectivity (product ratio, 3.2 : 1) and the predominant formation of 2-adamantanol is unique and quite different from those (ca 1 : 1 mostly adamantanone/1-adamantanol) of autoxidation.This is the first successful ω-hydroxylase model.
- Tabushi, Iwao,Nakajima, Toshio,Seto, Kiyotomo
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- π-Face diastereoselection: Stereochemistry and reactivity of reduction reactions on conformationally rigid substrates: 5-X-adamantan-2-ones and trans-10-X-decal-2-ones
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Stereochemistry and relative rates kax and keq of reduction reactions on title compounds have been measured under four different reaction conditions (NaBH4 in i-PrOH, LiBH4 and NaAlH4 in THF and LiAlH4 in Et2O). Reaction sensitivities show that the Group III element has a prominent role in determining the structure of the transition state shape.
- Di Maio, Giorgio,Innella, Carolina,Vecchi, Elisabetta
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- The selective functionalisation of saturated hydrocarbons. Part 41. The use of Cu(II)/H2O2 and Cu(I)/H2O2 systems in pyridine
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The Cu(II)/H2O2 and Cu(I)/H2O2 systems for the functionalisation of saturated hydrocarbons are presented. A mechanism is proposed.
- Barton, Derek H. R.,Delanghe, Nathalie C.,Patin, Henri
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- Functional aspects of Gif-type oxidation of hydrocarbons mediated by iron picolinate H2O2-dependent systems: Evidence for the generation of carbon- and oxygen-centered radicals
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The present investigation explores the functional features of several novel and other previously ill-defined ferrous and ferric complexes of the picolinic acid anion (Pic), which are used to mediate Gif-type oxidation of hydrocarbons by H2O2. Complexes [Fe(Pic)2(py)2], [Fe(Pic)3]·0.5py, [Fe2O(Pic)4(py)2], [Fe2(μ-OH)2(Pic)4], and FeCl3 have been employed in oxygenations of adamantane by H2O2 mostly in py/AcOH to reveal that tert- and sec-adamantyl radicals are generated in Gif solutions. The alleged absence of sec-adamantyl radicals from Gif product profiles has been previously interpreted as compelling evidence in support of a non-radical mechanism for the activation of secondary C-H sites in Gif chemistry. The product profile is entirely dictated by trapping of the diffusively free adamantyl radicals, since authentic tert- and sec-adamantyl radicals are shown to partition between dioxygen and protonated pyridine at 4% O2 (in N2), or between dioxygen and TEMPO at 100% O2, in a manner analogous to that observed in Gif oxygenations of adamantane. The low tert/sec selectivity (2.2-4.5) obtained, increasing with increasing dioxygen partial pressure, and the small intramolecular kinetic isotope effect values revealed by employing adamantane-1,3-d2 (1.06(6) (Ar); 1.73(2) (4% O2 in N2)), indicate the presence of an indiscriminate oxidant under inert atmosphere, coupled to a more selective oxidant at higher partial pressures of dioxygen. Gif oxygenation of DMSO by H2O2 mediated by [Fe(Pic)2(py)2] provides pyridine-trapped methyl radicals under argon, as expected for the addition reaction of hydroxyl radicals to DMSO. The reaction is progressively inhibited by increasing amounts of EtOH, generating pyridine-captured CH3·CHOH and ·CH2CH2OH radicals. Quantification of the DMSO- versus EtOH-derived alkyl radicals affords an estimate of k(EtOH)/k(DMSO) equal to 0.34(3), in reasonable agreement with the kinetics of radiolytically produced hydroxyl radicals (k(EtOH)/k(DMSO) = 0.29). The formation of methyl radicals in Gif oxygenation of DMSO is also supported by the quantitative generation of tert-adamantyl radicals in the presence of 1-iodoadamantane. These results are consistent with the action of hydroxyl radicals in Gif oxygenations by Fe(II/III)/H2O2 (Ar), most likely coupled to substrate-centered alkoxyl radicals under O2. The oxygen-centered radicals perform H-atom abstractions from Gif substrates to generate diffusively free carbon-centered radicals, in accord with previously reported findings.
- Kiani, Salma,Tapper, Amy,Staples, Richard J.,Stavropoulos, Pericles
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- 74. Polar Effects. Part 12. Inductivity and Carbon Participation in the Solvolysis of 4-Substituted 2-Adamantyl Arenesulfonates
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The rate constants (log k) for the solvolysis of 4e-substituted 2e- and 2a-adamantyl p-nitrobenzenesulfonates 14 and 15, respectively, in 80percent EtOH correlate linearly with the respective inductive substituent constants ?qI.Therefore, relative rates are controlled by the I effect of the substituents at C(4).The derived reaction constants, or inductivities, ρI of -0.80 and -0.64 for the series 14 and 15, respectively, are far smaller than those previously determined for 6-substituted 2-norbornyl and 2-bicyclooctyl sulfonates, in which the partial structure containing the substituent and the leaving group is the same.The ratio of the retained and inverted adamantanols obtained upon hydrolysis of the series 14 falls from 2.85 for R=CH3 to ca. 1 for R=CN, i.e. as the substituent at C(4) becomes more electron-attracting.In the 2a-series 15 this ratio is uniformly higher.These findings confirm that the 2-adamantyl cation is weakly bridged and that through-space induction in carbocations involves graded bridging of the cationic center by neighboring C-atoms.
- Grob, Cyril A.,Wittwer, Gerhard,Rao, K. Rama
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- Rate and product studies with 2-adamantyl fluoroformate under solvolytic conditions
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The specific rates of solvolysis of 2-adamantyl fluoroformate have been measured at 25.0°C in 20 pure and binary solvents. These are well correlated using the extended Grunwald-Winstein equation, with incorporation of the N T solvent nucleophilicity scale and the YCl solvent ionizing power scale. The sensitivities (l = 2.15±0.17 and m = 0.95±0.07) toward the changes in solvent nucleophilicity and solvent ionizing power, and the kF/kCl values are very similar to those previously observed for solvolyses of n-octyl fluoroformate, consistent with the addition step of an addition-elimination pathway being rate-determining. For aqueous ethanol, measurement of the product ratio allowed selectivity values (5) to be determined. The results are compared with those reported earlier for 2-adamantyl chloroformate and mechanistic conclusions are drawn. Copyright
- Kyong, Jin Burm,Rhu, Chan Joo,Kim, Yong-Gun,Kevill, Dennis N.
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- Perchlorate Esters. 7. Solvolysis of 2-Adamantyl Perchlorate: Rate and Product Studies
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The solvolysis of 2-adamantyl perchlorate proceeds at a convenient rate at temperatures close to ambient in a wide variety of pure and aqueous organic solvents.The nucleofugality of the perchlorate ion in SN1 reactions is shown to be several orders of magnitude higher than for more conventional leaving groups, such as p-toluenesulfonate or bromide.Entropies of activation in pure organic solvents nd in 80percent ethanol are unusually high.Grunwald-Winstein plots are markedly curved, with deviations being especially marked for aqueous-acetone and aqueous-2,2,2-trifluoroethanol mixtures.A scale of YOClO3 values is developed and compared with scales for a variety of other leaving groups.In aqueous ethanol there is a preference for product formation by interaction with water molecules by a factor of ca. 1.7, essentially independent of solvent composition (96-50percent ethanol) and temperature.
- Kevill, Dennis N.,Bahari, Mohd. S.,Anderson, Steven W.
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- OXONE AS OXYGEN DONOR IN THE CATALYTIC HYDROXYLATION OF SATURATED HYDROCARBONS.
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Manganese porphyrin complexes catalyze the hydroxylation of saturated hydrocarbons by potassium hydrogen persulfate (or Oxone) at room temperature.High conversions of hydrocarbons are obtained.
- Poorter, Bertha de,Ricci, Marko,Meunier, Bernard
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- Hydrogen-atom and oxygen-atom transfer reactivities of iron(
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A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F?, Cl?; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that
- Banerjee, Sridhar,Haukka, Matti,Hossain, Md. Kamal,Huelsmann, Ricardo Dagnoni,Martendal, Edmar,Munshi, Sandip,Nordlander, Ebbe,Paine, Tapan K.,Peralta, Rosely,Singh, Reena,Sinha, Arup,Valiati, Andrei Felipe,Wendt, Ola F.,Xavier, Fernando,Yiga, Solomon
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supporting information
p. 870 - 884
(2022/02/01)
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- Non-Heme-Iron-Mediated Selective Halogenation of Unactivated Carbon?Hydrogen Bonds
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Oxidation of the iron(II) precursor [(L1)FeIICl2], where L1 is a tetradentate bispidine, with soluble iodosylbenzene (sPhIO) leads to the extremely reactive ferryl oxidant [(L1)(Cl)FeIV=O]+ with a cis disposition of the chlorido and oxido coligands, as observed in non-heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C?H abstraction and the result of a rebound of the ensuing radical to an iron-bound Cl?. The time-resolved formation of the halogenation product indicates that this primarily results from sPhIO oxidation of an initially formed oxido-bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe2+ and Fe3+ in comparison with [(L1)FeIICl2] indicate a high complex stability of the bispidine-iron complexes. DFT analysis shows that, due to a large driving force and small triplet-quintet gap, [(L1)(Cl)FeIV=O]+ is the most reactive small-molecule halogenase model, that the FeIII/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects.
- Bleher, Katharina,Comba, Peter,Faltermeier, Dieter,Gupta, Ashutosh,Kerscher, Marion,Krieg, Saskia,Martin, Bodo,Velmurugan, Gunasekaran,Yang, Shuyi
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supporting information
(2021/12/09)
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- KF-Promoted copper-catalyzed highly efficient and selective oxidation of methane and other alkanes with a dramatic additive effect
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Highly efficient oxidation of methane to methyl trifluoroacetate mediated by CuCl/KF/K2S2O8in trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) is described. The additive effect has been systematically evaluated and potassium fluoride (KF) was identified as the most effective promoter among the salts screened. KF is conjectured to exhibit the salt effect to promote the [SO4˙]?radical to escape the solvent cage based on control experiments. Cyclohexane and adamantane could also be efficiently oxidized into benzene or corresponding trifluoroacetates.
- Chen, Wei,Chen, Xiaoyan,Fan, Wu,Li, Suhua,Liu, Luyao
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p. 4962 - 4968
(2021/07/26)
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- Cationic nickel(II) pyridinophane complexes: Synthesis, structures and catalytic activities for C-H oxidation
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A series of nickel(II) pyridinophane complexes were synthesized and characterized by X-ray crystallographic analysis. Their IR spectra supported the existence of mononuclear nickel(II) complexes in solution. Furthermore, we conducted catalytic CH oxidation of cyclooctane with nickel(II) pyridinophanes as the catalysts. The activity of nickel(II) pyridinophanes was affected by steric hindrance around the nitrogen atoms.
- Nishimura, Tsubasa,Ando, Yuki,Shinokubo, Hiroshi,Miyake, Yoshihiro
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supporting information
p. 1049 - 1052
(2021/05/19)
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- Selective Aerobic Oxidation of Secondary C (sp3)-H Bonds with NHPI/CAN Catalytic System
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Abstract: The direct aerobic oxidation of secondarty C(sp3)-H bonds was achieved in the presence of N-hydroxyphthalimide (NHPI) and cerium ammonium nitrate (CAN) under mild conditions. Various benzylic methylenes could be oxidized to carbonyl compounds in satisfied selectivity while saturated cyclic alkanes could be further oxidized to the corresponding lactones with the catalytic system. Remarkably, 25% of isochroman was converted to corresponding ketone with a selectivity of 96%. The reaction was initiated by hydrogen atom abstraction from NHPI by cerium and nitrates under oxygen atmosphere to form PINO radicals. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) addition experiments showed that the oxidation proceeded via a complex radical chain mechanism and an ion pathway. Graphic Abstract: [Figure not available: see fulltext.]
- Wang, Lingyao,Zhang, Yuanbin,Yuan, Haoran,Du, Renfeng,Yao, Jia,Li, Haoran
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p. 1663 - 1669
(2020/10/21)
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- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Scope and limitations of biocatalytic carbonyl reduction with white-rot fungi
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The reductive activity of various basidiomycetous fungi towards carbonyl compounds was screened on an analytical level. Some strains displayed high reductive activities toward aromatic carbonyls and aliphatic ketones. Utilizing growing whole-cell cultures of Dichomitus albidofuscus, the reactions were up-scaled to a preparative level in an aqueous system. The reactions showed excellent selectivities and gave the respective alcohols in high yields. Carboxylic acids were also reduced to aldehydes and alcohols under the same conditions. In particular, benzoic, vanillic, ferulic, and p-coumaric acid were reduced to benzyl alcohol, vanillin, dihydroconiferyl alcohol and 1-hydroxy-3-(4-hydroxyphenyl)propan, respectively.
- Zhuk, Tatyana S.,Skorobohatko, Oleksandra S.,Albuquerque, Wendell,Zorn, Holger
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supporting information
(2021/02/02)
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- Cationic ruthenium(II)–NHC pincer complexes: Synthesis, characterisation and catalytic activity for transfer hydrogenation of ketones
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Cationic ruthenium pincer complexes, [Ru(CNC)(CO)(PPh3)Cl]X (CNC = 2,6-bis(1-methylimidazol-2-ylidene)-pyridine, X = Cl? [1a], PF6? [1b]), [Ru(CNC)(PPh3)2Cl]X (X = Cl? [2a], PF6? [2b]) and [Ru(CNC)(PPh3)2(H)]X (X = Cl? [3a], PF6? [3b]) with triphenylphosphine, CO and halides as coligands have been synthesised and characterised by 1H, 13C, 31P NMR, mass and single-crystal X-ray crystallography. The application of Ru complexes in the transfer hydrogenation of a wide range of ketones with 2-propanol as the hydrogen source is explored. The in situ transformations observed during the synthesis help understand and suggest a plausible mechanism via the hydride complex 3b. All complexes appear to be efficient catalyst precursors for transfer hydrogenation of ketones.
- Yadav, Dibya,Misra, Shilpi,Kumar, Dheeraj,Singh, Suryabhan,Singh, Amrendra K.
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- Ruthenium complex based on [N,N,O] tridentate -2-ferrocenyl-2-thiazoline ligand for catalytic transfer hydrogenation
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A method for the synthesis of a new phosphine-free [N,N,O]-tridentate Schiff base ligand L1 using the 2-Ferrocenyl-2-thiazoline as scaffold was developed. The 1,2-disubstituted ferrocene-based ligand was assembled using as key strategy the directed ortho-metalation (DoM) in 2-ferrocenyl-2-thiazoline. L1 was successfully obtained in 83% of overall yield after two-step synthesis. The coordination ability of L1 towards Ru(II) was evidenced and the resulting complex was characterized by IR, UV-vis and EPR. Its catalytic performance was tested in transfer hydrogenation of a variety of substrates giving moderate to excellent conversions.
- Badillo-Gómez,Sánchez-Rodríguez,Toscano,Gouygou,Ortega-Alfaro,López-Cortés
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- Mixed-metal MOFs as efficient catalysts for transfer hydrogenation of furfural, levulinic acid and other carbonyl compounds
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Crystalline, porous Fe-Ni mixed-metal metal-organic frameworks (MOFs), namely MIL-88B(Fe2Ni) and NH2-MIL-88B(Fe2Ni), were synthesized and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, atomic absorption spectrophotometry (AAS) and nitrogen physisorption measurements. The MOFs were then employed as catalysts for transfer hydrogenation (TH) of biomass derivatives such as furfural and levulinic acid, and various other carbonyl compounds using 2-propanol as a sacrificial hydrogen donor. These heterogeneous catalysts are deemed to be environmentally benign, efficient and recyclable. NH2-MIL-88B(Fe2Ni) showcased good catalytic activity with low catalyst loading in short reaction time. The catalysts were recovered and reused several times without significant degradation in catalytic activity. A mechanism for the TH reaction was also proposed. As far as we are aware, this is the first report on the synthesis of furfuryl alcohol and γ-valerolactone (GVL) via TH reaction in just 60 min using a MOF catalyst.
- Karvembu, Ramasamy,Raja, Duraisamy Senthil,Sindhuja, Dharmalingam,Swaminathan, Srividya,Vasanthakumar, Punitharaj
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- Robust Mn(iii): N -pyridylporphyrin-based biomimetic catalysts for hydrocarbon oxidations: heterogenization on non-functionalized silica gel versus chloropropyl-functionalized silica gel
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Two classes of heterogenized biomimetic catalysts were prepared and characterized for hydrocarbon oxidations: (1) by covalent anchorage of the three Mn(iii) meso-tetrakis(2-, 3-, or 4-pyridyl)porphyrin isomers by in situ alkylation with chloropropyl-functionalized silica gel (Sil-Cl) to yield Sil-Cl/MnPY (Y = 1, 2, 3) materials, and (2) by electrostatic immobilization of the three Mn(iii) meso-tetrakis(N-methylpyridinium-2, 3, or 4-yl)porphyrin isomers (MnPY, Y = 4, 5, 6) on non-modified silica gel (SiO2) to yield SiO2/MnPY (Y = 4, 5, 6) materials. Silica gel used was of column chromatography grade and Mn porphyrin loadings were deliberately kept at a low level (0.3% w/w). These resulting materials were explored as catalysts for iodosylbenzene (PhIO) oxidation of cyclohexane, n-heptane, and adamantane to yield the corresponding alcohols and ketones; the oxidation of cyclohexanol to cyclohexanone was also investigated. The heterogenized catalysts exhibited higher efficiency and selectivity than the corresponding Mn porphyrins under homogeneous conditions. Recycling studies were consistent with low leaching/destruction of the supported Mn porphyrins. The Sil-Cl/MnPY catalysts were more efficient and more selective than SiO2/MnPY ones; alcohol selectivity may be associated with hydrophobic silica surface modification reminiscent of biological cytochrome P450 oxidations. The use of widespread, column chromatography, amorphous silica yielded Sil-Cl/MnPY or SiO2/MnPY catalysts considerably more efficient than the corresponding, previously reported materials with mesoporous Santa Barbara Amorphous No 15 (SBA-15) silica. Among the materials studied, in situ derivatization of Mn(iii) 2-N-pyridylporphyrin by covalent immobilization on Sil-Cl to yield Sil-Cl/MnP1 showed the best catalytic performance with high stability against oxidative destruction and reusability/recyclability.
- Pinto, Victor Hugo A.,Falc?o, Nathália K. S. M.,Mariz-Silva, Bárbara,Fonseca, Maria Gardennia,Rebou?as, Júlio S.
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supporting information
p. 16404 - 16418
(2020/12/03)
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- Catalytic oxyfunctionalization of saturated hydrocarbons by non-heme oxo-bridged diiron(III) complexes: role of acetic acid on oxidation reaction
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Oxo-bridged diiron(III) complexes [Fe2O(L1)2(H2O)2](ClO4)4 (1) and [Fe2O(L2)2(H2O)2](ClO4)4 (2), where L1 and L2 are tetradentate N-donor N,N′-bis(2-pyridylmethyl)-1,2-cyclohexanediamine and N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine respectively, have been isolated as synthetic models of non-heme iron oxygenases and characterized by physicochemical and spectroscopic methods. Both the complexes have been studied as catalysts for the oxyfunctionalization of saturated hydrocarbons using green hydrogen peroxide (H2O2) as oxidant under mild conditions. The selectivity (A/K) and regioselectivity (3°/2°) in oxidative C–H functionalization of alkanes suggests the involvement of metal-based intermediate in the oxygenation reaction. The catalytic efficiency is found to be strongly dependent on the presence of acetic acid. Remarkable increase in conversion and selectivity favoring the formation of alcohols in the oxidation of cyclohexane and cyclooctane and exclusive hydroxylation of adamantane with drastic enhancement of regioselectivity has been achieved by the addition of acetic acid in the presence of H2O2.
- Agarwalla, Uday Sankar
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p. 583 - 588
(2020/07/14)
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- Iron(III) 5,15-diazaporphyrin catalysts for the direct oxidation of C(sp3)-H bonds
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5,15-Diazaporphyrins are porphyrin analogues with imine-type sp2-hybridized nitrogen atoms at the meso-positions. Even though these compounds are more electron-deficient than regular porphyrins, the use of iron diazaporphyrins as catalysts has not been reported. Herein, we disclose the synthesis, structure, and electronic properties of iron(III) 5,15-diazaporphyrins. We evaluate their structures and electronic natures by X-ray analysis and electrochemical analyses. We also demonstrate that chloroiron(III) 5,15-diazaporphyrins exhibit high catalytic activity in the direct oxidation of alkanes due to their intrinsic electron-deficient nature. On the basis of stoichiometric reactions of iron(III) diazaporphyrin with iodosylbenzene as an oxidant, it was possible to demonstrate the existence of an iodosylbenzene-iron diazaporphyrin adduct reaction intermediate that serves as a reservoir to generate oxo-iron species.
- Ikeue, Takahisa,Miyake, Yoshihiro,Nishimura, Tsubasa,Shinokubo, Hiroshi,Shoji, Osami
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supporting information
p. 15751 - 15756
(2020/11/20)
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- Efficient alkane hydroxylation catalysis of nickel(ii) complexes with oxazoline donor containing tripodal tetradentate ligands
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Tris(oxazolynylmethyl)amine TOAR(where R denotes the substituent groups on the fourth position of the oxazoline rings) complexes of nickel(ii) have been synthesized as catalyst precursors for alkane oxidation withmeta-chloroperoxybenzoic acid (m-CPBA). The molecular structures of acetato, nitrato,meta-chlorobenzoato and chlorido complexes with TOAMe2have been determined using X-ray crystallography. The bulkiness of the substituent groups R affects the coordination environment of the nickel(ii) centers, as has been demonstrated by comparison of the molecular structures of chlorido complexes with TOAMe2and TOAtBu. The nickel(ii)-acetato complex with TOAMe2is an efficient catalyst precursor compared with the tris(pyridylmethyl)amine (TPA) analogue. Oxazolynyl donors’ strong s-electron donating ability will enhance the catalytic activity. Catalytic reaction rates and substrate oxidizing position selectivity are controlled by the structural properties of the R of TOAR. Reaction of the acetato complex with TOAMe2andm-CPBA yields the corresponding acylperoxido species, which can be detected using spectroscopy. Kinetic studies of the decay process of the acylperoxido species suggest that the acylperoxido species is a precursor of an active species for alkane oxidation.
- Hikichi, Shiro,Horii, Sena,Nakazawa, Jun,Okamura, Masaya,Terao, Ikumi
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p. 6108 - 6118
(2020/05/25)
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- Diethylsilane as a Powerful Reagent in Au Nanoparticle-Catalyzed Reductive Transformations
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Diethylsilane (Et2SiH2), a simple and readily available dihydrosilane, that exhibits superior reactivity, as compared to monohydrosilanes, in a series of reductive transformations catalyzed by recyclable and reusable Au nanoparticles (1 mol-%) supported on TiO2. It reduces aldehydes or ketones almost instantaneously at ambient conditions. It can be used in a one pot rapid reductive amination procedure, in which premixing of aldehyde and amine is required prior to the addition of the reducing agent and the catalyst, even in a protic solvent. An unprecedented method for the synthesis of N-arylisoindolines is also shown in the reductive amination between o-phthalaldehyde and anilines. In this transformation, it is proposed that the intermediate N,2-diphenylisoindolin-1-imines are reduced stepwise to the isoindolines. Finally, Et2SiH2 readily reduces amides into amines in excellent yields and shorter reaction times relative to previously known analogous nano Au(0)-catalyzed protocols.
- Louka, Anastasia,Kidonakis, Marios,Saridakis, Iakovos,Zantioti-Chatzouda, Elisavet-Maria,Stratakis, Manolis
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p. 3508 - 3514
(2020/06/02)
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- Iron and chromium MOFs as sustainable catalysts for transfer hydrogenation of carbonyl compounds and biomass conversions
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MIL-88B is a class of metal-organic framework (MOF) that has been widely explored in catalysis. Iron- and chromium-based MIL-88B MOFs were prepared and characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and N2 adsorption/desorption measurements. The MIL-88B MOFs were investigated as catalysts for transfer hydrogenation (TH) of carbonyl compounds (ketones and aldehydes) and biomass derivatives (levulinic acid and furfural) with 2-propanol as a hydrogen donor. Their conversion and selectivity were excellent. The recovered catalyst was reused ten times, with no significant loss in catalytic activity. The recovered catalyst after the tenth run retained its original crystallinity and morphology, which were confirmed by SEM and powder XRD studies. Catalyst reusability for levulinic acid (LA) conversion was also studied. The activation energy for the transformation of LA to γ-valerolactone (GVL) was 25.44 kJ mol-1. The catalytic performance of MIL-88B(Fe) was compared with that of MIL-53(Fe).
- Karvembu, Ramasamy,Lin, Chia-Her,Senthil Raja, Duraisamy,Sindhuja, Dharmalingam,Vasanthakumar, Punitharaj
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p. 8223 - 8231
(2020/06/10)
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- New copper(II) coordination compounds assembled from multifunctional pyridine-carboxylate blocks: Synthesis, structures, and catalytic activity in cycloalkane oxidation
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Two new copper(II) coordination compounds, namely a 1D coordination polymer [Cu(μ-cpna)(phen)(H2O)]n (1) and a discrete tetracopper(II) derivative [Cu(phen)2(H2O)]2[Cu2(μ-Hdppa)2(Hdppa)2] (2), were hydrothermally synthesized from copper(II) chloride as a metal source, 5-(4-carboxyphenoxy)nicotinic acid (H2cpna) or 5-(3,4-dicarboxylphenyl)picolinic acid (H3dppa) as a principal building block, and 1,10-phenanthroline (phen) as a crystallization mediator. Compounds 1 and 2 were isolated as air-stable microcrystalline solids and fully characterized by elemental and thermogravimetric analyses, IR spectroscopy, powder and single-crystal X-ray diffraction. In the solid state, the structure of 1 discloses the linear interdigitated 1D coordination polymer chains with the 2C1 topology. The crystal structure of an ionic derivative 2 shows that the mono-and dicopper(II) units are extended into the intricate 1D hydrogen-bonded chains with the SP 1-periodic net (4,4)(0,2) topology. Thermal stability and catalytic properties of 1 and 2 were also investigated. In fact, both Cu derivatives act as efficient homogeneous catalysts (catalyst precursors) for the mild oxidation of cycloalkanes by hydrogen peroxide to give the corresponding alcohols and ketones; the substrate scope and the effects of type and amount of acid promoter as well as bond-, regio-, and stereo-selectivity features were investigated.
- Zhao, Na,Li, Yu,Gu, Jinzhong,Fernandes, Tiago A.,Kirillova, Marina V.,Kirillov, Alexander M.
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supporting information
(2019/01/14)
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- Ruthenium Aqua Complexes Supported by the Kl?ui Tripodal Ligand: Synthesis, Structure, and Application in Catalytic C–H Oxidation in Water
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Water-soluble ruthenium(III) aqua complexes supported by the Kl?ui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]– (LOEt–) have been synthesized and structurally characterized, and their use as catalysts for C–H oxidation in water has been studied. The treatment of [Ru(LOEt)Cl2(MeCN)] with N-donor ligands afforded the adducts [Ru(LOEt)Cl2(L)] (L = tBuNH2 (1), pyridine (2), imidazole (3)). Refluxing [Ru(LOEt)Cl2(MeCN)] in neat tBuNH2 gave the amidine complex [Ru(LOEt)Cl2{N(H)C(Me)NHtBu}] (4). Chloride abstraction of 1–3 with AgOTs (OTs = tosylate) in 1 M p-toluenesulfonic acid afforded the water-soluble RuIII diaqua complexes [Ru(LOEt)(H2O)2(L)](OTs)2 (L= tBuNH2 (5), pyridine (6), imidazole (7)), whereas that for 4 yielded the triaqua complex [Ru(LOEt)(H2O)3](OTs)2 (8). The crystal structures of 4, 5, 7, and 8 have been determined. The reduction of 5 with Zn dust in D2O gave a diamagnetic RuII species, whereas that in MeCN led to isolation of the RuII acetonitrile complex [RuII(LOEt)(MeCN)2(tBuNH2)](PF6) (9), which has been characterized by X-ray diffraction. The RuIII aqua complexes proved to be moderately efficient catalysts for C–H bond oxidation with tert-butyl hydroperoxide in water. For example, the oxidation of ethylbenzene with tert-butyl hydroperoxide in water at room temperature in the presence of 0.1 mol-% of 8 afforded acetophenone in ca. 62 % yield.
- So, Yat-Ming,Wong, Kang-Long,Sung, Herman H. Y.,Williams, Ian D.,Leung, Wa-Hung
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p. 2368 - 2374
(2019/05/15)
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- Potential Synthetic Adaptogens: V. Synthesis of Cage Monoamines by the Schwenk–Papa Reaction
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The reduction of cage ketoximes under Schwenk–Papa reaction conditions was studied to establish that the d,l, d- and l-camphor oximes are smoothly reduced to the corresponding amines in high yields. At the same time, d,l-norcamphor and adamantan-2-one oximes undergo partial catalytic deoximation to form a mixture of the corresponding amines and alcohols.
- Brunilin, R. V.,Mkrtchyan, A. S.,Nawrozkij, M. B.,Novakov, I. A.,Vernigora, A. A.,Voloboev, S. N.,Vostrikova, O. V.
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p. 1742 - 1748
(2020/01/11)
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- Design of Manganese Phenol Pi-complexes as Shvo-type Catalysts for Transfer Hydrogenation of Ketones
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Catalytic hydrogenation is one of the most important reactions both in academic research and industry. We explored ability of the manganese pi-complexes to act as Shvo-type catalysts for transfer hydrogenation of ketones. DFT calculations suggested that the transfer of hydrogen atoms from the hypothetical intermediate [(C6Me3H2OH)Mn(CO)2H] to acetone has low activation barrier of 10.9 kcal mol?1. Experimentally a number of ketones with various functional groups (OMe, NH2, Cl, CF3, pyridyl) were successfully reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex.
- Shvydkiy, Nikita V.,Vyhivskyi, Oleksandr,Nelyubina, Yulia V.,Perekalin, Dmitry S.
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p. 1602 - 1605
(2019/03/07)
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- Half-sandwich Ru (II) complexes containing (N, O) Schiff base ligands: Catalysts for base-free transfer hydrogenation of ketones
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Two new half-sandwich Ru (II)(p-cymene) complexes (1 and 2) containing dopamine-based (N, O) Schiff base ligands (L1H and L2H) were synthesized and characterized by FT-IR, UV–Visible and 1H & 13C NMR spectral techniques, and elemental analyses. The spectroscopic and analytical data revealed monobasic bidentate coordination of the ligands with Ru ion. The molecular structures of L1H, L2H and 2 were further confirmed by single crystal X-ray diffraction study. Complexes 1 and 2?have been employed as catalysts in the transfer hydrogenation of ketones using 2-propanol as a hydrogen source at 85?°C under base-free condition. Good to the excellent yield of secondary alcohols, gram scale synthesis, and high TON and TOF made this catalytic system interesting.
- Satheesh,Sathish Kumar, Pushpanathan N.,Kumara, P. Raghavendra,Karvembu, Ramasamy,Hosamani, Amar,Nethaji
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- Photoelimination of nitrogen from adamantane and pentacycloundecane (PCU) diazirines: A spectroscopic study and supramolecular control
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Photochemical reactivity of pentacycloundecane (PCU) and adamantane diazirines was investigated by preparative irradiation in different solvents, laser flash photolysis (LFP) and quantum chemical computations. In addition, formation of inclusion complexes for diazirines with cucurbit[7]uril, β- and γ-cyclodextrin (β- and γ-CD) was investigated by 1H NMR spectroscopy, isothermal microcalorimetry and circular dichroism spectroscopy, followed by the investigation of photochemical reactivity of the formed complexes. Diazirines undergo efficient photochemical elimination of nitrogen (ΦR > 0.5) and deliver the corresponding singlet carbenes. Singlet carbenes react in intra- and intermolecular reactions and we found a rare singlet carbene pathway in CH3OH involving protonation and formation of a carbocation, detected due to the specific rearrangement of the pentacycloundecane skeleton. Singlet diazirines undergo intersystem crossing and deliver triplet carbenes that react with oxygen to form ketones which were isolated after irradiation. Our main finding is that the formation of diazirine inclusion complexes with β-CD and γ-CD changes the relative ratio of singlet vs. triplet pathways, with singlet carbene products being dominant from the chemistry of the irradiated complexes. Our combined theoretical and experimental studies provide new insights into the supramolecular control of carbene reactivity which has possible applications for the control of product distribution by solvent effects and the choice of constrained media.
- ?umanovac, Tatjana,Ale?kovi?, Marija,?ekutor, Marina,Matkovi?, Marija,Baron, Thibaut,Mlinari?-Majerski, Kata,Bohne, Cornelia,Basari?, Nikola
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p. 1806 - 1822
(2019/07/16)
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- Nanoporous Na+-montmorillonite perchloric acid as an efficient and recyclable catalyst for the chemoselective protection of hydroxyl groups
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Nanoporous Na+-montmorillonite perchloric acid as a novel heterogeneous reusable solid acid catalyst was easily prepared by treatment of Na+-montmorillonite as a cheap and commercially available support with perchloric acid. The catalyst was characterized using a variety of techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), pH analysis and determination of the Hammett acidity function. The prepared reagent showed excellent catalytic activity for the chemoselective conversion of alcohols and phenols to their corresponding trimethylsilyl ethers with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) at room temperature. Deprotection of the resulting trimethylsilyl ethers can also be carried out using the same catalyst in ethanol. All reactions were performed under mild and completely heterogeneous reaction conditions in good to excellent yields. The notable advantages of this protocol are: short reaction times, high yields, availability and low cost of the reagent, easy work-up procedure and the reusability of the catalyst during a simple filtration.
- Mashhadinezhad, Maryam,Shirini, Farhad,Mamaghani, Manouchehr
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p. 2099 - 2107
(2019/01/03)
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- Bioinspired Olefin cis-Dihydroxylation and Aliphatic C-H Bond Hydroxylation with Dioxygen Catalyzed by a Nonheme Iron Complex
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A mononuclear iron(II)-α-hydroxy acid complex [(TpPh,Me)FeII(benzilate)] (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate) of a facial tridentate ligand has been isolated and characterized to explore its catalytic efficiency for aerial oxidation of organic substrates. In the reaction between the iron(II)-benzilate complex and O2, the metal-coordinated benzilate is stoichiometrically converted to benzophenone with concomitant reduction of dioxygen on the iron center. Based on the results from interception experiments and labeling studies, different iron-oxygen oxidants are proposed to generate in situ in the reaction pathway depending upon the absence or presence of an external additive (such as protic acid or Lewis acid). The five-coordinate iron(II) complex catalytically cis-dihydroxylates olefins and oxygenates the C-H bonds of aliphatic substrates using O2 as the terminal oxidant. The iron(II) complex exhibits better catalytic activity in the presence of a Lewis acid.
- Chatterjee, Sayanti,Bhattacharya, Shrabanti,Paine, Tapan Kanti
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p. 10160 - 10169
(2018/08/28)
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- Interplay between H-bonding and interpenetration in an aqueous copper(ii)-aminoalcohol-pyromellitic acid system: self-assembly synthesis, structural features and catalysis
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Two new copper(ii) coordination compounds, [Cu(H1.5mdea)2]2(H2pma) (1a) and [{Cu2(μ-Hmdea)2}2(μ4-pma)]n·2nH2O (1b), were self-assembled at different temperatures from the same multicomponent reaction system, comprising copper(ii) nitrate, N-methyldiethanolamine (H2mdea), pyromellitic acid (H4pma), and potassium hydroxide. Products 1a and 1b were isolated as microcrystalline solids and fully characterized and their structures were established by single-crystal X-ray diffraction. Compound 1a features the bis-aminoalcohol(ate) monocopper(ii) units and H2pma2? anions that are multiply interconnected by strong H-bonds into a firm 2D H-bonded layer. Compound 1b reveals the bis-aminoalcoholate dicopper(ii) motifs that are interlinked by the μ4-pma4? spacers into a 3D + 3D interpenetrated metal-organic framework. From a topological perspective, both networks of 1a and 1b are uninodal and driven by similar 4-connected H2pma2? or pma4? nodes, but result in distinct sql and dia topologies, respectively. Compound 1a was applied as an efficient catalyst for two model cycloalkane functionalization reactions: (1) oxidation by H2O2 to form cyclic alcohols and ketones and (2) hydrocarboxylation by CO/H2O and S2O82? to form cycloalkanecarboxylic acids. The substrate scope, effects of various reaction parameters, selectivity and mechanistic features were also investigated.
- Fernandes, Tiago A.,Kirillova, Marina V.,André, Vania,Kirillov, Alexander M.
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p. 16674 - 16683
(2018/12/05)
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- Liquid-phase oxidation of alkanes with molecular oxygen catalyzed by high valent iron-based perovskite
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Hexagonal BaFeO3-δ containing high valent iron species acted as an efficient heterogeneous catalyst for the aerobic oxidation of alkanes without the need for additives. The activity of BaFeO3-δ was much higher than that of typical Fe3+/Fe2+-containing iron oxide-based catalysts, and the recovered catalyst could be reused without significant loss of catalytic performance.
- Shibata, Satomi,Sugahara, Kosei,Kamata, Keigo,Hara, Michikazu
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supporting information
p. 6772 - 6775
(2018/06/26)
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- Transfer hydrogenation of ketones catalyzed by iridium-bulky phosphine complexes
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The complexes [Ir(COD)(PR3)2]PF6 (R = PPh3 (1); R = PBn3 = tribenzylphosphine (2)), [Ir(COD)(PBn3)(PAn3)]PF6 (3) (PAn3 = Tri-orthoanisyl-phosphine) and cis-(P,P)-[IrH(COD)(PBn3){η2-P,C-(C6H4CH2)PBn2}]PF6 (4) are active in the transfer hydrogenation of ketones. However, complex (3) gives the best results in conversion toward the alcohol. Interestingly, commercial isopropanol was used as hydrogen source, without any drying treatment. In situ generated isopropoxide was used as base. An efficient conversion of a variety of ketones, aromatic or aliphatic, cyclic or linear, including molecules with conjugated or isolated C[dbnd]C moieties was achieved, thus reporting 12 examples of hydrogenated substrates. Ketones of higher steric hindrance could not be converted under the studied conditions. The experimental evidence indicates that the steric and electronic properties of the substrates are determinant in the observed conversions and performance of the system. For α,β-unsaturated ketones, preference toward the reduction of the C[dbnd]C bond was observed. However, the system shows chemoselectivity toward the carbonyl group in molecules which also bear an isolated C[dbnd]C moiety. With the results obtained, a pseudo first-order dependence of the reaction rate on the concentration of ketone was determined. Also, stoichiometric as well as in situ tests were performed to shed light into the reaction pathways possibly involved in the catalytic TH of ketones described herein (precursor 3, base and isopropyl alcohol as hydrogen source).
- Landaeta, Vanessa R.,Rosa, Abel D. Salazar-La,Rodríguez-Lugo, Rafael E.
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p. 303 - 311
(2017/09/06)
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- An air and moisture tolerant iminotrihydroquinoline-ruthenium(ii) catalyst for the transfer hydrogenation of ketones
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Reaction of 8-amino-5,6,7,8-tetrahydroquinoline with RuCl2(PPh3)3 at room temperature affords the ruthenium(ii) chelate (8-NH2-C9H10N)RuCl2(PPh3)2 (E), in which the two triphenylphosphine ligands are disposed mutually cis. By contrast, when the reaction is performed at reflux ligand oxidation/dehydrogenation occurs along with cis-trans reorganization of the triphenylphosphines to form the 8-imino-5,6,7-trihydroquinoline-ruthenium(ii) complex, (8-NH-C9H9N)RuCl2(PPh3)2 (F). Complex F can also be obtained in higher yield by heating a solution of E alone to reflux. Comparison of their molecular structures highlights the superior binding properties of the bidentate imine ligand in F over its amine-containing counterpart in E. Both complexes are highly effective in the transfer hydrogenation of a wide range of alkyl-, aryl- and cycloalkyl-containing ketones affording their corresponding secondary alcohols with loadings of as low as 0.1 mol%. Significantly, F can deliver excellent conversions even in bench quality 2-propanol in reaction vessels open to the air, whereas the catalytic efficiency of E is diminished by the presence of air but only operates efficiently under inert conditions.
- Li, Jiaoyan,Ma, Yingmiao,Wang, Zheng,Liu, Qingbin,Solan, Gregory A.,Ma, Yanping,Sun, Wen-Hua
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p. 8738 - 8745
(2018/07/13)
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- [N,P]-pyrrole-phosphine ligand: An efficient and robust ligand for Ru-catalyzed transfer hydrogenation microwave-assisted reactions
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A pyrrolyl-containing [N-P]-ligand (L1) and [Ru] were evaluated as catalytic system in transfer hydrogenation reaction of ketones. A comparison between microwave irradiation vs conventional heating conditions indicates that MW can be successfully used as energy source, improving the reaction time. The L1/Ru(II) proved to be an active, efficient and robust catalytic system. The scope of this catalytic system was evaluated using a diversity of substrates that include electron-withdrawing and electron-donor groups achieving a range of 65 to 95% conversion. Moreover, the catalytic system showed good activity even with highly sterically hindered ketones.
- Sánchez-Rodríguez,Fragoso-Medina,Ramírez-Meneses,Gouygou,Ortega-Alfaro,López-Cortés
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- Chemoselective transfer hydrogenation of nitroarenes, ketones and aldehydes using acylthiourea based Ru(II)(p-cymene) complexes as precatalysts
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A new series of Ru(II)(η6-p-cymene) complexes (1–5) was synthesized from pyridine based acylthiourea ligands (L1-L5) and [Ru(η6-p-cymene)Cl2]2. All the ligands and complexes were well characterized by UV-Visible, FT-IR, mass and 1H & 13C NMR spectroscopic techniques. The molecular structures of the ligands (L1, L2, L4 and L5) and complex 1 were confirmed using single crystal X-ray diffraction study. The Ru(II)(η6-p-cymene) complexes (1–5) were proved to be efficient precatalysts for the transfer hydrogenation of carbonyl compounds and nitroarenes in the presence of 2-propanol as a hydrogen donor and KOH as a base. The catalytic transfer hydrogenation reactions were chemoselective towards the nitro group in presence of carbonyl group, which is a rare scenario in homogeneous catalysis. The catalyst was compatible with broad range of substrates which include furfural, quinone and many heterocycles. The catalytic reactions exhibited very high conversions (upto 100%) and excellent yields (upto 99%). Turn Over Number (TON) was found upto 990.
- Sathishkumar, Pushpanathan N.,Raveendran, Neethi,Bhuvanesh, Nattamai S.P.,Karvembu, Ramasamy
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- Reliably Regioselective Dialkyl Ether Cleavage with Mixed Boron Trihalides
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A protocol for the regioselective cleavage of unsymmetrical alkyl ethers to generate alkyl alcohol and alkyl bromide products is described. A mixture of trihaloboranes triggers this conversion and exhibits improved reactivity profiles (regioselectivity and yield) compared with BBr3 alone. Additionally, this procedure allows the efficient synthesis of (B-Cl) dialkyl boronate esters. There are limited methods to generate acyclic dialkoxyboryl chlorides, and these intermediates constitute important synthons in main-group chemistry.
- Atienza, Bren Jordan P.,Truong, Nam,Williams, Florence J.
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p. 6332 - 6335
(2018/10/09)
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- Stereospecific sp3 C–H oxidation with m-CPBA: A CoIII Schiff base complex as pre-catalyst vs. its CoIIICdII heterometallic derivative
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The mono- and binuclear Schiff base complexes [CoL3]·DMF (1) and [CoCdL3Cl2]·0.5H2O (2) were facilely synthesized using zerovalent cobalt and cadmium chloride (for 2) as starting materials and the pre-formed pro-ligand HL (2-methoxy-6-[(methylimino)methyl]phenol, the product of condensation of o-vanillin and methylamine) in air. The compounds were characterized by single crystal X-ray diffraction analysis and spectroscopic methods in solution and in the solid state. Both complexes demonstrate a profound catalytic activity in the stereoselective oxidation of cis-1,2-dimethylcyclohexane (model substrate) with m-CPBA (m-chloroperbenzoic acid) under mild conditions in the presence of promoters of various acidity (HNO3, TFA and HOAc). The heterometallic binuclear CoIIICdII pre-catalyst (2) was more active than the mononuclear CoIII one (1), exhibiting higher products yields up to 51% and excellent stereospecificity (up to 99.2% retention of stereoconfiguration). This result could be associated with a synergistic effect of two different metals in 2. Based on the large obtained kinetic isotope effect and H218O labeling studies, the overall reaction mechanism was proposed to proceed without the participation of free alkyl radicals. The acidity of the promoter was shown to influence catalytic parameters for both 1 and 2 so that the better parameters are achieved with the acid possessing lower pKa values (a stronger acid). The comparison of the catalytic behaviours of 1 and 2 is discussed in detail considering relevant examples from the literature.
- Nesterova, Oksana V.,Kasyanova, Katerina V.,Makhankova, Valeriya G.,Kokozay, Vladimir N.,Vassilyeva, Olga Yu.,Skelton, Brian W.,Nesterov, Dmytro S.,Pombeiro, Armando J.L.
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p. 171 - 184
(2018/05/28)
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- Neutral Dinuclear Copper(I)-NHC Complexes: Synthesis and Application in the Hydrosilylation of Ketones
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The synthesis of a class of highly stable neutral dinuclear Cu(I)-NHC complexes using 1,2,4-triazole as a bridging ligand is described. Various NHCs were used to generate a library of [Cu(μ-trz)(NHC)]2 complexes. Interestingly, [Cu(μ-trz)(IPr)]2 was found to be highly active in the hydrosilylation of ketones, without the need for an external base or any other additive. A wide range of aryl and alkyl ketones, as well as sterically hindered ketones, was successfully reduced to alcohols using the lowest catalyst loading reported to date.
- Trose, Michael,Lazreg, Fa?ma,Chang, Tao,Nahra, Fady,Cordes, David B.,Slawin, Alexandra M. Z.,Cazin, Catherine S. J.
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p. 238 - 242
(2017/06/07)
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- Nickel-catalyzed reduction of ketones with water and triethylsilane
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The acetophenone (1a) reduction using catalytically active nickel complexes and water is an efficient and sustainable method to access a new methodology of transfer hydrogenation of ketones. When triethylsilane (Et3SiH) was used as sacrificial agent to promote the transfer hydrogenation from water, 1-phenylethanol (2a) was obtained in excellent yield along with silanol (Et3SiOH) as the reaction's driving force. Deuterium labeling studies were made using Et3SiD or D2O and these studies showed that both compounds participate as hydride sources for the ketone reduction. A scope of substrates was assessed, including a variety of mono/diketones, and α,β-unsaturated ketones, to yield the corresponding secondary alcohols and saturated ketones. Additionally, asymmetric transfer hydrogenation of mono-ketones was studied for the mixture of nickel/(bisphosphine or phospholane) as catalyst precursor, using H2O/Et3SiO system and ethanol as hydrogen sources.
- Castellanos-Blanco, Nahury,Flores-Alamo, Marcos,García, Juventino J.
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p. 324 - 332
(2017/06/29)
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- Hydroxylation versus Halogenation of Aliphatic C?H Bonds by a Dioxygen-Derived Iron–Oxygen Oxidant: Functional Mimicking of Iron Halogenases
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An iron–oxygen intermediate species generated in situ in the reductive activation of dioxygen by an iron(II)–benzilate complex of a monoanionic facial N3ligand, promoted the halogenation of aliphatic C?H bonds in the presence of a protic acid and a halide anion. An electrophilic iron(IV)–oxo oxidant with a coordinated halide is proposed as the active oxidant. The halogenation reaction with dioxygen and the iron complex mimics the activity of non-heme iron halogenases.
- Chatterjee, Sayanti,Paine, Tapan Kanti
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supporting information
p. 7717 - 7722
(2016/07/07)
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- Aerobic alcohol oxidation and oxygen atom transfer reactions catalyzed by a nonheme iron(II)-α-keto acid complex
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α-Ketoglutarate-dependent enzymes catalyze many important biological oxidation/oxygenation reactions. Iron(iv)-oxo intermediates have been established as key oxidants in these oxidation reactions. While most reported model iron(ii)-α-keto acid complexes exhibit stoichiometric reactivity, selective oxidation of substrates with dioxygen catalyzed by biomimetic iron(ii)-α-keto acid complexes remains unexplored. In this direction, we have investigated the ability of an iron(ii) complex [(TpPh,Me)FeII(BF)] (1) (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazolyl)borate and BF = monoanionic benzoylformate) to catalyze the aerobic oxidation of organic substrates. An iron-oxo oxidant, intercepted in the reaction of 1 with O2, selectively oxidizes sulfides to sulfoxides, alkenes to epoxides, and alcohols to the corresponding carbonyl compounds. The oxidant from 1 is able to hydroxylate the benzylic carbon of phenylacetic acid to afford mandelic acid with the incorporation of one oxygen atom from O2 into the product. The iron(ii)-benzoylformate complex oxidatively converts phenoxyacetic acids to the corresponding phenols, thereby mimicking the function of iron(ii)-α-ketoglutarate-dependent 2,4-dichlorophenoxyacetate dioxygenase (TfdA). Furthermore, complex 1 exhibits catalytic aerobic oxidation of alcohols and oxygen atom transfer reactions with multiple turnovers.
- Sheet, Debobrata,Paine, Tapan Kanti
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p. 5322 - 5331
(2016/08/02)
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- Formation and High Reactivity of the anti-Dioxo Form of High-Spin μ-Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C-H Bonds
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Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O-O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene8]toluene is 95 at -30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2O2. Strong anti oxidant: A high-spin μ-oxodioxodiiron(IV) species undergoes transformation from the syn-dioxo to the anti-dioxo form, which cleaves strong C-H bonds of alkanes. The high-spin anti-dioxodiiron(IV) species with a sterically less hindered structure (see figure) is a highly reactive and selective oxidant. These results provide insight into the high reactivity of the active species Q of soluble methane monooxygenases and the development of efficient alkane oxidation catalysts.
- Kodera, Masahito,Ishiga, Shin,Tsuji, Tomokazu,Sakurai, Katsutoshi,Hitomi, Yutaka,Shiota, Yoshihito,Sajith,Yoshizawa, Kazunari,Mieda, Kaoru,Ogura, Takashi
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p. 5924 - 5936
(2016/04/26)
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- Nickel-catalyzed transfer hydrogenation of ketones using ethanol as a solvent and a hydrogen donor
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We report a nickel(0)-catalyzed direct transfer hydrogenation (TH) of a variety of alkyl-aryl, diaryl, and aliphatic ketones with ethanol. This protocol implies a reaction in which a primary alcohol serves as a hydrogen atom source and solvent in a one-pot reaction without any added base. The catalytic activity of the nickel complex [(dcype)Ni(COD)] (e) (dcype: 1,2-bis(dicyclohexyl-phosphine)ethane, COD: 1,5-cyclooctadiene), towards transfer hydrogenation (TH) of carbonyl compounds using ethanol as the hydrogen donor was assessed using a broad scope of ketones, giving excellent results (up to 99% yield) compared to other homogeneous phosphine-nickel catalysts. Control experiments and a mercury poisoning experiment support a homogeneous catalytic system; the yield of the secondary alcohols formed in the TH reaction was monitored by gas chromatography (GC) and NMR spectroscopy.
- Castellanos-Blanco, Nahury,Arévalo, Alma,García, Juventino J.
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p. 13604 - 13614
(2016/09/04)
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- Rapid probing of the reactivity of P450 monooxygenases from the CYP116B subfamily using a substrate-based method
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Developing a detailed understanding of the reactivity of self-sufficient Type IV P450 monooxygenases, four types of O-methylated substrates were designed as probes, including monoterpenes, cycloalkanes, aromatic compounds and steroids, and the efficiency of their oxyfunction was determined using a colorimetric assay which was based on the reaction between the enzymatic demethylation product, formaldehyde, and Purpald dye. The activity-based fingerprints of new P450RpMO, P450ArMO and P450CtMO (CYP116B members) indicated that CYP116B P450s preferentially oxidize substrates with aromatic components. Moreover, the hydroxylated products were detected based on the preference results. This rapid and efficient strategy, when coupled with GCMS, enables the exploration of the reactivity of other CYP116B members.
- Li, Ren-Jie,Xu, Jian-He,Yin, Yue-Cai,Wirth, Nicolas,Ren, Jiang-Meng,Zeng, Bu-Bing,Yu, Hui-Lei
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supporting information
p. 8928 - 8934
(2016/10/13)
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- Colloid and nanosized catalysts in organic synthesis: XII. Hydrogenation of carbonitriles catalyzed by nickel nanoparticles
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Hydrogenation of carbonitriles catalyzed by nickel nanoparticles in isopropanol proceeds under atmospheric pressure of hydrogen within 6-15 h to yield mainly secondary amines. Hydrogenation of α-aminonitriles results in reductive decyanation. β-Aminonitriles undergo hydrogenolysis at the nitrogen-carbon bond.
- Mokhov,Popov,Shcherbakova
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p. 273 - 280
(2016/04/20)
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- New highly brominated Mn-porphyrin: A good catalyst for activation of inert C-H bonds
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This work describes the synthesis and characterization of a novel third-generation catalyst 5,10,15,20-tetrakis-(4′-bromine-3′,5′-dimethoxyphenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese chloride [MnIIIBr12T3,5DMPP]Cl (Cat.2). The catalytic activity of Cat.2 in cyclohexane, adamantane, and n-hexane oxidation by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc)2) was compared with the catalytic activity of [MnIIIT3,5DMPP]Cl (Cat.1), a second generation catalyst. The Cat.2/PhI(OAc)2 system led to higher yields of cyclohexane oxidation products (65%) with high selectivity for cyclohexanol (86%) as compared with Cat.1 (19% and 74%, respectively) and addition of water essentially did not alter total product yield. Addition of a small amount of imidazole to the Cat.1/PhIO system gave superior yields of cyclohexane oxidation products (64%) as compared with Cat.2 (52%). In all systems Cat.2 afforded significantly higher yields of 2-adamantanol, a product with great commercial value compared with 1-adamantanol. n-Hexane oxidation gave low total product yield; Cat.2 was more selective for alcohol products (2-hexanol and 3-hexanol).
- Santos Da Silva, Vinicius,Nakagaki, Shirley,Ucoski, Geani Maria,Idemori, Ynara Marina,DeFreitas-Silva, Gilson
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p. 106589 - 106598
(2016/01/08)
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- Catalytic Oxidation of Alkanes and Alkenes by H2O2 with a μ-Oxido Diiron(III) Complex as Catalyst/Catalyst Precursor
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A new μ-oxo diiron(III) complex of the lithium salt of the pyridine-based unsymmetrical ligand 3-[(3-{[bis(pyridin-2-ylmethyl)amino]methyl}-2-hydroxy-5-methylbenzyl)(pyridin-2-ylmethyl)amino]propanoate (LiDPCPMPP), [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, has been synthesized and characterized. The ability of the complex to catalyze oxidation of several alkanes and alkenes has been investigated by using CH3COOH/H2O2 (1:1) as an oxidative system. Moderate activity in cyclohexane oxidation (TOF = 33 h-1) and good activity in cyclohexene oxidation (TOF = 72 h-1) were detected. Partial retention of configuration (RC = 53%) in cis- and trans-1,2-dimethylcyclohexane oxidation, moderate 3/2 selectivity (4.1) in adamantane oxidation, and the observation of a relatively high kinetic isotope effect for cyclohexane oxidation (KIE = 3.27) suggest partial metal-based oxidation, probably in tandem with free-radical oxidation. Low-temperature UV/Vis spectroscopy and mass spectrometric studies in the rapid positive detection mode indicate the formation of a transient peroxido species, [Fe2(O)(O2)(LiDPCPMPP)2]2+, which might be an intermediate in the metal-based component of the oxidation process. A μ-oxido diiron(III) complex, [Fe2(μ-O)(LiDPCPMPP)2](ClO4)2, was synthesized and characterized. This complex was used as catalyst in C-H bond oxidation with CH3COOH-H2O2 as chemical oxidant. Reactivity studies indicate that the oxidation process goes through a metal-based mechanism concomitant with a radical process.
- Das, Biswanath,Al-Hunaiti, Afnan,Haukka, Matti,Demeshko, Serhiy,Meyer, Steffen,Shteinman, Albert A.,Meyer, Franc,Repo, Timo,Nordlander, Ebbe
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p. 3590 - 3601
(2015/08/06)
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- Biomimetic alkane oxidation by iodosylbenzene and iodobenzene diacetate catalyzed by a new manganese porphyrin: Water effect
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This work describes the synthesis and characterization of the novel third-generation catalyst 5,10-(3,5-bromo,4-aminophenyl)-15,20-(phenyl)-2,3,7,8,12,13,17,18-octabromoporphyrinatomanganese(III) chloride, cis-[MnIIIBr12DAPDPP]Cl, and compares the catalytic activity of this compound with the catalytic activity of the first- and second-generation manganese porphyrins [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl, respectively, in cyclohexane, adamantane and n-hexane, oxidation by iodosylbenzene (PhIO) or iodobenzene diacetate (PhI(OAc)2). This work also investigates how addition of water and imidazole influences the catalytic systems in the adamantane and cyclohexane oxidation. In the absence of water and imidazole, cis-[MnIIIBr12DAPDPP]Cl leads to higher product yields as compared with [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl in cyclohexane oxidation. The third-generation (β-octabrominated) cis-[MnIIIBr12DAPDPP]Cl was not fully destroyed in reactions with PhI(OAc)2 as oxidant. In the presence of imidazole, [MnIIITPP]Cl and cis-[MnIIIDAPDPP]Cl give superior cyclohexanol yields as compared with cis-[MnIIIBr12DAPDPP]Cl. Addition of water during adamantane oxidation by PhI(OAc)2 increases 1-adamantanol yield. As for cyclohexane oxidation by PhIO or PhI(OAc)2, the presence of water raises product yields and diminishes catalyst destruction, especially in the case of cis-[MnIIIDAPDPP]Cl. The presence of water in systems employing PhI(OAc)2 as oxidant affords higher product yields as compared with systems that use PhIO as oxidant.
- Da Silva, Vinícius Santos,Idemori, Ynara Marina,DeFreitas-Silva, Gilson
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- Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C-H Bonds with Stereoretention
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An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [FeII(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol-1) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tandem with kinetic analysis show that the 490 nm chromophore of 2 is associated with two S = 1/2 species in rapid equilibrium. The minor component 2a (～5% iron) has g-values at 2.20, 2.19, and 1.99 characteristic of a low-spin iron(III) center, and it is assigned as [FeIII(OOAc)(PyNMe3)]2+, also by comparison with the EPR parameters of the structurally characterized hydroxamate analogue [FeIII(tBuCON(H)O)(PyNMe3)]2+ (4). The major component 2b (～40% iron, g-values = 2.07, 2.01, 1.95) has unusual EPR parameters, and it is proposed to be [FeV(O)(OAc)(PyNMe3)]2+, where the O-O bond in 2a has been broken. Consistent with this assignment, 2b undergoes exchange of its acetate ligand with CD3CO2D and very rapidly reacts with olefins to produce the corresponding cis-1,2-hydroxoacetate product. Therefore, this work constitutes the first example where a synthetic nonheme iron species responsible for stereospecific and site selective C-H hydroxylation is spectroscopically trapped, and its catalytic reactivity against C-H bonds can be directly interrogated by kinetic methods. The accumulated evidence indicates that 2 consists mainly of an extraordinarily reactive [FeV(O)(OAc)(PyNMe3)]2+ (2b) species capable of hydroxylating unactivated alkyl C-H bonds with stereoretention in a rapid and site-selective manner, and that exists in fast equilibrium with its [FeIII(OOAc)(PyNMe3)]2+ precursor.
- Serrano-Plana, Joan,Oloo, Williamson N.,Acosta-Rueda, Laura,Meier, Katlyn K.,Verdejo, Bego?a,García-Espa?a, Enrique,Basallote, Manuel G.,Münck, Eckard,Que, Lawrence,Company, Anna,Costas, Miquel
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supporting information
p. 15833 - 15842
(2016/01/09)
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- Olefin cis-Dihydroxylation and Aliphatic C-H Bond Oxygenation by a Dioxygen-Derived Electrophilic Iron-Oxygen Oxidant
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Many iron-containing enzymes involve metal-oxygen oxidants to carry out O2-dependent transformation reactions. However, the selective oxidation of C-H and C-C bonds by biomimetic complexes using O2 remains a major challenge in bioinspired catalysis. The reactivity of iron-oxygen oxidants generated from an FeII-benzilate complex of a facial N3 ligand were thus investigated. The complex reacted with O2 to form a nucleophilic oxidant, whereas an electrophilic oxidant, intercepted by external substrates, was generated in the presence of a Lewis acid. Based on the mechanistic studies, a nucleophilic FeII-hydroperoxo species is proposed to form from the benzilate complex, which undergoes heterolytic O-O bond cleavage in the presence of a Lewis acid to generate an FeIV-oxo-hydroxo oxidant. The electrophilic iron-oxygen oxidant selectively oxidizes sulfides to sulfoxides, alkenes to cis-diols, and it hydroxylates the C-H bonds of alkanes, including that of cyclohexane. Lewis acid mediated O-O bond cleavage: A nucleophilic iron(II)-hydroperoxo oxidant, formed upon oxidative decarboxylation of an iron(II)-α-hydroxy acid complex, undergoes heterolytic O-O bond cleavage in the presence of a Lewis acid to generate an electrophilic iron(IV)-oxo-hydroxo oxidant. The electrophilic oxidant oxidizes sulfides to sulfoxides and alkenes to cis-diols, and it hydroxylates the strong C-H bonds of aliphatic substrates.
- Chatterjee, Sayanti,Paine, Tapan Kanti
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supporting information
p. 9338 - 9342
(2015/08/06)
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- Selective synthesis of primary amines by reductive amination of ketones with ammonia over supported Pt catalysts
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Supported platinum catalysts are studied for the reductive amination of ketones under ammonia and hydrogen. For a model reaction with 2-adamantanone, Pt-loaded MoOx/TiO2 (Pt-MoOx/TiO2) shows the highest yield of primary amine. The catalyst is effective for the selective transformation of various aliphatic and aromatic ketones to the corresponding primary amines, which demonstrates the first example of the selective synthesis of primary amines by this reaction. The yield of the amine increases with increase in the negative shift of the C￡O stretching band in the infrared spectra of adsorbed acetone on the catalysts, suggesting that Lewis acid sites on the support material play an important role in this catalytic system.
- Nakamura, Yoichi,Kon, Kenichi,Touchy, Abeda Sultana,Shimizu, Ken-Ichi,Ueda, Wataru
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p. 921 - 924
(2015/03/18)
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- Ultrasound promoted preparation of Mn(III)-porphyrin nanoparticles: An efficient heterogeneous catalyst for oxidation of alkenes, alkanes and sulfides
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In the present research meso-tetrakis(4-carboxyphenyl)porphyrinatomanganese(III) acetate (Mn(TCPP)OAc) nanoparticles have been prepared for the first time without any stabilizing agent or supporting matrix under ultrasonic irradiation. Scanning electron microscopy (SEM) was used to characterize and investigate the nanocatalyst. Rapid, efficient, facile and highly selective oxidation of a wide range of olefins by tetra-n-butylammonium hydrogen monopersulfate over the prepared manganese nanocatalyst was investigated. Also oxidation of sulfides and alkanes in the presence of the (Mn(TCPP)OAc) nanoparticles were studied. The catalyst is recovered by filtration and reused at least five times.
- Rayati, Saeed,Nejabat, Fatemeh,Naghashian, Nasireh
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p. 1232 - 1237
(2016/02/18)
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