Cyclization reactions of methylthioacetanilides

The cyclization reactions of methylthioacetanilides mediated by manganese(III) acetate and/or copper(II) acetate are described. Indolinones and indolinediones can be produced effectively via a 5-membered ring cyclization of methylthioacetanilides. The product distributions are highly dependent on the reaction conditions. In most cases, the electronic effect of the substituents on the aryl ring was found to significantly affect the yields of cyclization products. This cyclization reaction proceeded faster with manganese(III) acetate/copper(II) acetate.     

A novel manganese(III)-peroxo complex bearing a proline-derived pentadentate aminobenzimidazole ligand

A novel nonheme manganese(III)-peroxo complex bearing a proline-derived pentadentate aminobenzimidazole ligand was synthesized and spectroscopically characterized, and its reactivity in aldehyde deformylation was investigated.     

The oxidation of Co2(CO)8, Mn2(CO)10 and Fe(CO)5 by dibenzoyl peroxide. Kinetics and mechanism

Summary Dicobalt octacarbonyl in toluene solution can be quantitatively oxidized at room temperature with dibenzoyl peroxide to cobalt(II) benzoate and carbon monoxide. The rate of CO evolution is first order in dicobalt octacarbonyl, first order in dibenzoyl peroxide, and negative first order in CO. Similar behaviour leading to manganese(II) benzoate is observed with dimanganese decacarbonyl. Sixteen electron rather than seventeen electron intermediates are involved in these reactions. In contrast to the dinuclear carbonyls, Fe(CO)₅ is oxidized by dibenzoyl peroxide in an autocatalytic reaction.     

Solid State Conductivity and Catalytic Activity of Hexacyanoferrate(II)–Thiosemicarbazide Complexes of 3d-Metals

The temperature dependence of the resistivity of tablets of hexacyanoferrate(II)–thiosemicarbazide complexes of chromium(III), manganese(II), iron(III), cobalt(III), nickel(II), copper(II), and zinc(II) was measured in the range 20-90 °C. A relationship between the conductivity of a substance and the rate constant for the catalytic decomposition of hydrogen peroxide is established.     

Cu(OAc)2‐catalyzed partial oxidation of methane to methyl trifluoroacetate in the liquid phase

Simple transition‐metal salts were investigated as the catalysts for the partial oxidation of methane. In trifluoroacetic acid (TFA), methane could be efficiently converted to methyl trifluoroacetate by the Cu(OAc)₂/K₂S₂O₈ catalyst system. A quantitative yield (96.3%) based on methane has been obtained under the optimized conditions. A possible mechanism involving radical intermediates has been suggested for this reaction. Copyright © 2000 John Wiley & Sons, Ltd.     

Mangan(IV)-Komplexe mit dreizähnigen diaciden Liganden. Kristallstruktur von Acetylacetonato-salicylaldehydbenzoylhydrazonato(2−)-methanol-mangan(III)

Manganese(IV) Complexes with Tridentate Diacidic Ligands. Crystal Structure of Acetyl-acetonato-salicylaldehydebenzoylhydrazonato(2?)-methanol-manganese(III) The manganese(IV) chelates of salicylaldehyde benzoylhydrazone and salicylaldehyde salicylhydrazone were synthesized by ligand exchange reactions using bis(acetylacetonato)manganese(II), tris(acetylacetonato)manganese(III) as well as manganese(III) acetate. The brown complexes show the expected molecular ions in the APCI mass spectra. As an intermediate compound acetyacetonato-salicylaldehydebenzoylhydrazonato(2?)-methanol-manganese(III) was isolated and characterized by X-ray structural analysis. Crystallographic data see “Inhaltsübersicht”.     

Electrochemical reduction of the lanthanide ions: Part II. Second reduction step of europium(III), ytterbium(III) and samarium(III) in acidic tetramethylammonium perchlorate solution

The second reduction step of Eu(III), Yb(III) and Sm(III) in 0.04 M tetramethylammonium perchlorate in the pH range 1.8–7 was investigated by cyclic voltammetry and d.c. polarography. The proposed reaction scheme at large hydrogen ion/lanthanide ion concentration ratios involves the reduction of the lanthanide(II) ion to the metallic state accompanied by a surface catalytic reaction in which the reactant is regenerated and also hydroxyl ions are formed which induces the precipitation of lanthanide(II) hydrous oxide on the electrode surface. This lanthanide(II) hydroxide is reduced at more negative potentials than the hydrated lanthanide(II) species. At lower hydrogen ion/lanthanide ion concentration ratios a preceding chemical reaction, probably involving hydrolyzed lanthanide(II) species, becomes rate determining.     

Synthesis and characterization of manganese(IV) and ruthenium(III) complexes derived from bis (2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone

Bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone(naohH₄) interacts with manganese(II) acetate in methanol followed by addition of KOH giving [Mn^IV(naoh)(H₂O)₂]. Activated ruthenium(III) chloride reacts with naohH₄ in methanol yielding [Ru^III(naohH₄)Cl(H₂O)Cl₂]. The replacement of aquo by heterocyclic nitrogen donor in these complexes has been observed when the reaction is carried out in presence of heterocyclic nitrogen donors such as pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF for these complexes suggest non-electrolytic nature. Magnetic moment values suggest +4 oxidation state for manganese in its complexes, however, ruthenium(III) complexes are paramagnetic with one unpaired electron. Electronic spectral studies suggest six coordinate metal ions. IR spectra reveal that naohH₄ coordinates in enol-form and keto-form to manganese and ruthenium, respectively. ESR and cyclic voltammetric studies of the complexes have also been reported.     

Synthesis and structural characterization of manganese(III,IV) and ruthenium(III) complexes derived from 2-hydroxy-1-naphthaldehydebenzoylhydrazone

Reaction of 2-hydroxy-1-naphthaldehydebenzoylhydrazone(napbhH₂) with manganese(II) acetate tetrahydrate and manganese(III) acetate dihydrate in methanol followed by addition of methanolic KOH in molar ratio (2 : 1 : 10) results in [Mn(IV)(napbh)₂] and [Mn(III)(napbh)(OH)(H₂O)], respectively. Activated ruthenium(III) chloride reacts with napbhH₂ in methanolic medium yielding [Ru(III)(napbhH)Cl(H₂O)]Cl. Replacement of aquo ligand by heterocyclic nitrogen donor in this complex has been observed when the reaction is carried out in presence of pyridine(py), 3-picoline(3-pic) or 4-picoline(4-pic). The molar conductance values in DMF (N,N-dimethyl formamide) of these complexes suggest non-electrolytic and 1 : 1 electrolytic nature for manganese and ruthenium complexes, respectively. Magnetic moment values of manganese complexes suggest Mn(III) and Mn(IV), however, ruthenium complexes are paramagnetic with one unpaired electron suggesting Ru(III). Electronic spectral studies suggest six coordinate metal ions in these complexes. IR spectra reveal that napbhH₂ coordinates in enol-form and keto-form to manganese and ruthenium metal ions in its complexes, respectively. ESR studies of the complexes are also reported.     

Ru(III)-EDTA catalyzed oxidation of ascorbic acid by hydrogen peroxide in aqueous solution

The kinetics of oxidation of ascorbic acid to dehydroascorbic acid by hydrogen peroxide catalyzed by ethylenediaminetetraacetatoruthenate(III) has been studied over the pH range 1.50 – 2.50, at 30°C and μ = 0.1 M KNO₃. The reaction has a first-order dependence on ascorbic acid and Ru(III)-EDTA concentrations, an inverse first-order dependence on hydrogen ion concentration, and is independent of hydrogen peroxide concentration in the pH range studied. A mechanism has been proposed in which ascorbate anion forms a kinetic intermediate with the catalyst in a pre-equilibrium step. Ruthenium(III) is reduced to ruthenium(II) in a rate-determining step and is reoxidized with hydrogen peroxide back to the Ru(III) complex in a fast step.     

Biomimetic Decarboxylation of Carboxylic Acids with PhI（OAc）2 Catalyzed by Manganese Porphyrin [Mn（TPP）OAc]

Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.     

Synthesis,structure, and catalase-like activity of a novel manganese(II) complex: Dichloro[1,3-bis(2′-benzimidazolylimino)isoindoline]manganese(II)

Reaction of the ligand 1,3-bis(2′-benzimidazolylimino)isoindoline with manganese(II) chloride in acetonitrile/methanol leads to the novel mononuclear manganese(II) complex 1,3-bis(2′-benzimidazolylimino)isoindolinedichloro manganese(II) [Mn(bimindH)Cl₂], which has been characterized by various techniques such as elemental analysis, IR, UV–Vis, ESR spectroscopy, and X-ray diffraction. The ligand bimindH was synthesized by fusing phthalonitrile and 2-aminobenzimidazole at high temperature until ammonia evolution ceased. The catalase-like activity of the complex was tested in propionitrile, and it proved to be active in the dihydrogen peroxide dismutation. Based on kinetic studies the reaction is first-order in relation to both the complex and hydrogen peroxide.     

Manganese(III) acetate-mediated alkylation of beta-keto esters and beta-keto amides: an enantio- and diastereo-selective approach to substituted pyrrolidinones

beta-Keto esters and beta-keto amides can be efficiently alkylated on reaction with enol ethers and manganese(III) acetate in the presence of copper(II) acetate. These intermolecular radical addition reactions can be used to construct quaternary carbon centres in excellent yield and this method has been utilised in a diastereoselective approach to substituted pyrrolidinones.     

A synthesis of N-alkyl and N,N-dialkyl O-ethyl thiocarbamates from diethyl dixanthogenate using different oxidants

Abstract  

A novel synthesis of N-alkyl and N,N-dialkyl O-ethyl thiocarbamates from diethyl dixanthogenate and primary and secondary amines, using three oxidizing systems, has been developed on the laboratory scale, and the method using sodium hypochlorite has been applied on a semi-industrial scale. The effect of the oxidizing agents, sodium hypochlorite, in-situ-generated peracetic acid, and the manganese(II) acetate/oxygen system on product purity and yield was studied. The results obtained by use of these three methods were compared with those obtained by reaction of sodium ethyl xanthogenacetate and amines, and of sodium ethyl xanthate with amines in the presence of sulfated nickel zeolite catalyst. The reaction mechanism of sodium hypochlorite oxidation has been established on the basis of isolation of reaction intermediates and determination of their structure by use of Fourier-transform infrared, ¹H and ¹³C NMR, and mass spectrometric methods. The suggested sodium hypochlorite and manganese(II) acetate/oxygen systems have many advantages in comparison with commercial and catalytically promoted synthetic methods, because they are new ecologically friendly syntheses.     

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.     

2-Pyridinamin-Addukte von Übergangsmetall-bis(acetyl-acetonaten) und ihre Reaktionen. Hydrogencarbonat als Chelatligand in cis-(Ampy)2Co(acac)(HCO3)

2-Pyridinamine Adducts of Transition Metal Bis(acetylacetonates) and their Reactions. Hydrogencarbonate as a Chelating Ligand in cis-(Ampy)₂Co(acac)(HCO₃) The reaction of cobalt(II) salts, acetylacetone (acacH), 2-pyridinamine (Ampy), and the carbon dioxide of the air in methanol affords a mixture of (Ampy)₂Co(acac)₂( II ) and (Ampy)₂Co(CO₃)(H₂O)₂. On heating in toluene, appropriately in the presence of carbon dioxide, these complexes are converted into cis-(Ampy)₂Co(acac)(HCO₃) ( III ). Characteristic of compound III is a four-membered ring with the hydrogencarbonate as a bidentate ligand. The two Co? O distances are distinctly different (215.9 and 224.4 pm). In the complexes II and III 2-pyridinamine is a bidentate ligand coordinating by the endo-nitrogen. The Co-n-N bond lengths vary between 210.9 and 225.3 pm. Reasons are both the different trans-influence of the hydrogencarbonate or the acetylacetonato donor atoms and the π-interaction between cobalt(II) and the pyridine ring. This interaction is more significant in the cis-complex III . II and III are stabilized by a system of N? H …? O- and O? H …?O-bridges. With nickel(II) complexes analogous to II and III were obtained, while only the type II was characterized for manganese( II ).     

Partial oxidation of 4-tert-butyltoluene catalyzed by homogeneous cobalt and cerium acetate catalysts in the Br-/H2O2/acetic acid system: insights into selectivity and mechanism

The partial oxidation of 4-tert-butyltoluene to 4-tert-butylbenzaldehyde by hydrogen peroxide in glacial acetic acid, catalyzed by bromide ions in combination with cobalt(II) acetate or cerium(III) acetate, has been studied in detail. Based on the observed differences in reaction rates and product distributions for the different catalysts, a reaction mechanism involving two independent pathways is proposed. After the initial formation of a benzylic radical species, either oxidation of this intermediate by the metal catalyst or reaction with bromine generated in situ occurs, depending on which catalyst is used. The first pathway leads to the exclusive formation of 4-tert-butylbenzaldehyde, whereas reaction of the radical intermediate with bromine leads to formation of the observed side products 4-tert-butylbenzyl bromide and its hydrolysis and solvolysis products 4-tert-butylbenzyl alcohol and 4-tert-butylbenzyl acetate, respectively. The cobalt(II) catalysts Co(OAc)(2) and Co(acac)(2) are able to quickly oxidize the radical intermediate, thereby largely preventing the bromination reaction (i.e., side-product formation) from occurring, and yield the aldehyde product with 75-80 % selectivity. In contrast, the cerium catalyst studied here exhibits an aldehyde selectivity of around 50 % due to the competing bromination reaction. Addition of extra hydrogen peroxide leads to an increased product yield of 72 % (cerium(III) acetate) or 58 % (cobalt(II) acetate). Product inhibition and the presence of increasing amounts of water in the reaction mixture do not play a role in the observed low incremental yields.     

Kinetics and mechanism of oxidation of manganese(III) acidoporphyrin complexes with hydrogen peroxide

The reactions of manganese(III) acidotetraphenylporphyrin complexes with hydrogen peroxide in an aqueous-organic medium at 288–308 K are studied by spectrophotometry. The reaction is the oxidation of the manganese(III) complex. The spectral and kinetic data correspond to a multistep mechanism including the step of coordination of a hydrogen peroxide molecule by the central manganese atom. A possibility of formation of oxidized complexes without macrocycle destruction upon the reaction with H₂O₂ makes manganese(III) porphyrins quite promising for use as models of natural catalases.     

Oxidation of Arginine by Manganese(III) in Pyrophosphate and Acetate media: A kinetic study

Kinetics of manganese(III) oxidation of L-arginine has been studied in the presence of pyrophosphate and acetate ions in acidic media at 328 K and 323 K, respectively. The nature of the oxidizing species formed in manganese(III) solutions was determined by spectrophotometric and redox potential measurements. The reaction shows a first-order dependence on [manganese(III) pyrophosphate] in the pyrophosphate medium, pH 2–3, and a half-order on [manganese(III) acetate] in HOAc-acetate medium. In both media, the kinetic order is one with respect to [arginine]. The dependencies of the rate on the reduction product, manganese(II), concentration are zero- and inverse first-orders in acetate and pyrophosphate media, respectively. Effects of varying dielectric constant of the medium and of added anions such as acetate, pyrophosphate, fluoride, chloride, and perchlorate have been investigated, in both media. There is evidence for the existence of free radicals as transient species. Activation parameters have been evaluated using the Arrhenius and Eyring plots. Mechanisms consistent with the observed kinetic data have been proposed and discussed. Kinetic data for the oxidations of some α-amino acids by manganese(III) species of different forms are summarized and compared. © 1994 John Wiley & Sons, Inc.     

Hydroformylation of 1-Hexene Catalyzed by [Rh(COD)(2-Picoline)2]PF6 Immobilized on Poly(4-Vinylpyridine) Under Water Gas Shift Reaction Conditions

Reported here is the influence of the reaction conditions variation (1-hexene/rhodium content (S/C) = 16 - 105, temperature (T) = 70 - 110 °C and carbon monoxide pressure (P(CO)) = 0.6 - 1.8 atm) on the catalytic hydroformylation of 1-hexene to aldehydes (heptanal and 2-methyl-hexanal) by the rhodium(I) complex, [Rh(COD)(2-picoline)₂]PF₆ (COD = 1,5-cyclooctadiene)immobilized on poly(4-vinylpyridine) in contact with 10 mL of 80% aqueous 2-ethoxyethanol, under water gas shift reaction condition. This revised version was published online in June 2006 with corrections to the Cover Date.