Synthesis,X‐ray structure,characterization and catalytic activity of a polymeric manganese(II) complex with iminodiacetate

A polymeric manganese(II) complex with the general formula [Mn(O₂CCH₂NH₂CH₂CO₂)₂(H₂O)₂]_n from reaction of iminodiacetatic acid and manganese(II) perchlorate under nitrogen in water, was synthesized and characterized. The structure of the complex was determined using single‐crystal X‐ray diffraction, elemental analysis, IR and UV‐vis spectra. This complex exhibited excellent catalytic activity and selectivity for oxidation of various alcohols and sulfides to the corresponding aldehydes/ketone and sulfoxides using urea hydrogen peroxide and oxone (2KHSO₅·KHSO₄·K₂SO₄), respectively, as oxidants under air at room temperature. The easy preparation, mild reaction conditions, high yields of the products, short reaction time, no over‐oxidation products, high selectivity and inexpensive system make this catalytic system a useful method for oxidizing various alcohols and sulfides. Copyright © 2011 John Wiley & Sons, Ltd.     

Application and Mechanistic Studies of a Water‐Oxidation Catalyst in Alcohol Oxidation by Employing Oxygen‐Transfer Reagents

By using a dimeric ruthenium complex in combination with tert‐butyl hydrogen peroxide (TBHP) as stoichiometric oxidant, a mild and efficient protocol for the oxidation of secondary benzylic alcohols was obtained, thereby giving the corresponding ketones in high yields within 4 h. However, in the oxidation of aliphatic alcohols, the TBHP protocol suffered from low conversions owing to a competing Ru‐catalyzed disproportionation of the oxidant. Gratifyingly, by switching to Oxone (2 KHSO₅ ? KHSO₄ ? K₂SO₄ triple salt) as stoichiometric oxidant, a more efficient and robust system was obtained that allowed for the oxidation of a wide range of aliphatic and benzylic secondary alcohols, giving the corresponding ketones in excellent yields. The mechanism for these reactions is believed to involve a high‐valent Ru^V–oxo species. We provide support for such an intermediate by means of mechanistic studies.     

KHSO4 · H2O/SiO2‐Catalyzed,One‐Pot,Solvent‐Free Synthesis of Pyrazolines,Tetrahydrocarbozoles and Indoles using Microwave Irradiation

A new high‐yielding, operationally simple, solvent‐free, and mild method for preparation of pyrazolines, tetrahydrocarbazoles, and indoles has been developed using KHSO₄ · H₂O impregnated on SiO₂. The reactions have been probed under microwave irradiation (MWI), and ultrasonic and thermal conditions, employing different solid supports. The data revealed that KHSO₄ · H₂O impregnated on SiO₂ under MWI provides the best yields in a shorter time under solvent‐free reaction conditions.     

A new and highly effective method for catalytic oxidation of alcohols to the corresponding carbonyl compounds using the tris[(2-oxazolinyl)phenolato]manganese(III)/Oxone®/n-Bu4NBr oxidation system

Oxone® (2KHSO₅·KHSO₄·K₂SO₄) in the presence of mer-tris[(2-oxazolinyl)phenolato]manganese(III), Mn(phox)₃, as catalyst under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent efficiently oxidises alcohols to their corresponding aldehydes and ketones at room temperature with very short reaction times (5 min) and good to quantitative yields.     

Synthesis of gamma-hydroxy enones via persulfate oxidation of dienyl ethers.

The commercial oxidant “oxone” (2KHSO₄·K₂SO₄·KHSO₄) has been found to be a superior reagent for the gamma oxidation of dienyl ethers to axial gamma-hydroxy enones.     

Fast selective oxidation of alcohols under solvent-free conditions

A combination of acetic anhydride, H₂SO₄-nano silica, wet-SiO₂ (60 %), and K₂Cr₂O₇ as a new oxidizing system for the selective oxidation of different types of alcohols to the corresponding aldehydes and ketones at room temperature under solvent-free conditions is introduced. Mild reaction conditions, high yields of the products, short reaction time, no further oxidation to the corresponding carboxylic acid, and easy work-up make this new system a useful method for oxidizing alcohols.     

Synthesis,characterization, X-ray structural analysis and study of oxidative properties of tetraethylammonium chlorochromate

Tetraethylammonium chlorochromate(VI), Et₄N[CrO₃Cl] is easily synthesized in nearly quantitative yield using a direct reaction of chromium(VI) oxide and tetraethylammonium chloride and characterized by elemental analysis, IR, UV/Visible, ¹H-NMR and ¹³C-NMR techniques and single-crystal X-ray diffraction analysis (monoclinic system, space group C2(#5), with a = 12.023(3), b = 7.998(2), c = 14.527(4) Å, β = 114.187(4)°, V = 1274.4(6) ų and Z = 4). X-ray data determined the CH ··· O hydrogen bond that forms between the ethyl hydrogen of the cation and oxygen of the anion. This compound is a versatile reagent for efficient and selective oxidation of organic substrates, in particular for alcohols to their corresponding aldehydes or ketones, under mild conditions.     

One-pot synthesis of ketones and lactones by oxidation of the parent hydrocarbons with KHSO5 catalyzed by manganese(III) porphyrins in a biphasic,solid–liquid,system

The oxidation of alkanes to ketones and lactones by Oxone® (KHSO₄×K₂SO₄×2KHSO₅) catalyzed by manganese porphyrins has been studied in an anhydrous two-phase (solid Oxone®/DCE solution) catalytic system. Under the experimental conditions adopted, i.e., an excess of Oxone® over the organic substrate and catalytic amount of Mn(TDCPP)Cl, almost complete hydrocarbon conversions are obtained. Acyclic alkanes give ketones as main oxygenated product whereas cyclic alkanes give mainly lactones together with minor amounts of alcohols and ketones. The overall process leading to lactones involves two subsequent manganese porphyrin catalyzed oxidative steps and a stoichiometric reaction involving monopersulfate and the intermediate ketone. The lack of a water phase and of strong acids prevents the hydrolysis of the lactones formed. The products are obtained in yields ranging from low to fair depending on the nature of substrate, catalyst, and on phase transfer agent concentration.     

Two new silver(I) complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz): Preparation,characterization, crystal structure and alcohol oxidation activity in the presence of oxone

Two new silver(I) complexes ((tptz)Ag₂(NO₃)₂ and [Ag₅(tptz)₄](NO₃)₅) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) have been synthesized and characterized by X-ray diffraction, elemental analysis, ¹H NMR, IR, fluorescence, UV–Vis spectroscopy and electrochemistry. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted with one of the Ag complexes as a catalyst, soluble enough in organic solvent, using oxone (2KHSO₅·KHSO₄·K₂SO₄) as an oxidant under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature.     

Selective oxidation of benzylic,allylic and propargylic alcohols using dirhodium(II) tetraamidinate as catalyst and aqueous tert‐butyl hydroperoxide as oxidant

We show that the dirhodium(II) tetraamidinate complex Rh₂(Msip)₄ efficiently catalyzes the oxidation of activated secondary alcohols at only 0.1 mol% loading. In this approach, we oxidized various benzylic, allylic and propargylic alcohols to the corresponding carbonyl compounds under mild aqueous conditions using the inexpensive oxidant T‐HYDRO® (70 wt% aqueous tert‐butyl hydroperoxide). Copyright © 2015 John Wiley & Sons, Ltd.     

NaBrO3/NaHSO4 · H2O as a Versatile Reagent System for the Oxidation of Benzylic Alcohols and Aldehydes

The oxidation of benzylic alcohols and aldehydes by NaBrO₃ is efficiently promoted in the presence of NaHSO₄ · H₂O. All reactions were performed under mild and completely heterogeneous conditions in good to high yields.     

Efficient and selective oxidation of alcohols with <Emphasis Type="Italic">tert</Emphasis>-BuOOH catalyzed by a dioxomolybdenum(VI) Schiff base complex under organic solvent-free conditions

The catalytic activity of dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI) complex was studied, for the first time, in the selective oxidation of various primary and secondary alcohols using tert-BuOOH as oxidant under organic solvent-free conditions at room temperature. The effect of different solvents was studied in the oxidation of benzyl alcohol in this catalytic system. It was found that, under organic solvent-free conditions, the catalyst oxidized various primary and secondary alcohols to their corresponding aldehyde or ketone derivatives with high yield. The effects of other parameters such as oxidant and amount of catalyst were also investigated. Among different oxidants such as H₂O₂, NaIO₄, tert-BuOOH, and H₂O₂/urea, tert-BuOOH was selected as oxygen donor in the oxidation of benzyl alcohol. Also, it was found that oxidation of benzyl alcohol required 0.02 mmol catalyst for completion. Dioxomolybdenum(VI) Schiff base complex exhibited good catalytic activity in the oxidation of alcohols with tert-BuOOH under mild conditions. In this catalytic system, different primary alcohols gave the corresponding aldehydes in good yields without further oxidation to carboxylic acids.     

Reductive dehalogenation of halophenols in sulfite-bisulfate medium

The KHSO₄-Na₂SO₃ system is found to be simple and inexpensive for reductive elimination of halogens (Br, I) from the corresponding halophenols under reflux conditions in dry methanol. Under similar conditions the reaction is sluggish with chlorophenols.     

Kinetics of the gas‐phase reactions of hydroxyl radicals with C1–C6 aliphatic alcohols in the presence of ammonium sulfate aerosols

The effects of ammonium sulfate aerosols on the kinetics of the hydroxyl radical reactions with C₁–C₆ aliphatic alcohols have been investigated using the relative rate technique. P‐xylene was used as a reference compound for the C₂–C₆ aliphatic alcohols study, and ethanol was used as a reference compound for the methanol study. Two different aerosol concentrations that are typical of polluted urban conditions were tested. The total surface areas of aerosols were 1400 μm² cm^?3 (condition I) and 3400 μm² cm^?3 (condition II). Results indicate that ammonium sulfate aerosols promote the ethanol/OH radical and 1‐propanol/OH radical reactions as compared to the p‐xylene/OH radical reaction. The relative rate of the ethanol/·OH reaction versus the p‐xylene/·OH reaction increased from 0.19 ± 0.01 in the absence of aerosols to 0.24 ± 0.01 and 0.26 ± 0.02 under aerosol conditions I and II, respectively. The relative rate of the 1‐propanol/·OH reaction versus the p‐xylene/·OH reaction increased from 0.45 ± 0.03 in the absence aerosols to 0.56 ± 0.02 and 0.55 ± 0.03 under aerosol conditions I and II, respectively. However, significant changes in the relative rates of the 1‐butanol/·OH, 1‐pentanol/·OH, and 1‐hexanol/·OH reactions versus the p‐xylene/·OH reaction were not observed for either aerosol concentration. The relative rates of the methanol/·OH reaction versus the ethanol/·OH reaction were identical in the absence and presence of aerosols. These results indicate that ammonium sulfate aerosols promote the methanol/·OH reaction as much as the ethanol/·OH reaction (as compared to the p‐xylene/·OH reaction). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 422–430, 2001     

Solution structure of a seven coordinated manganese(II) complex via electrospray ionization mass spectrometry

The mononuclear complex [Mn(tptz)(CH₃COO)(OH₂)₂]NO₃ (1) was investigated by electrospray ionization mass spectrometry in aqueous solution at pH 4.5. Electrospray ionization mass spectrometry shows that mononuclear and dinuclear manganese cationic species are present in solution, probably in equilibrium with neutral 1. An experiment showed that the most important reaction in the presence of oxone (2KHSO₅·KHSO₄·K₂SO₄) is decoordination.     

Polymeric networks by the cationic crosslinking reaction of poly(allenyl ether)s having oligo(oxyethylene) moieties in the side chain

Cationic crosslinking reactions of poly(allenyl ether)s having oligo(oxyethylene) moieties prepared by the radical polymerization of the corresponding allenyl ethers were carried out under some varied reaction conditions. For instance, a crosslinked polymer was obtained in 82% yield by the treatment of poly(ethylene glycol methyl allenyl ether) ( 1a ) with 1.2 mol% of BF₃·OEt₂ ( 2 ) under high concentration in dichloromethane (46 wt %). The gels obtained showed good swelling properties in water, alcohols, and polar organic solvents such as dichloromethane. In particular, the degrees of swelling of these gels in aqueous sodium chloride (1M) were quite similar to those in ion-free water, indicating that these gels served as nonionic hydrogels. © 1994 John Wiley & Sons, Inc.     

RuCl3-DCHA Catalyst System: A Selective Aerobic Oxidation of Primary Benzylic Alcohols Under Mild Conditions

The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl₃ · 3H₂O–dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl₃ · 3H₂O–DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments.     

Oxidation of Alcohols and Pyridines by a Water-Soluble Polyoxometalate with Hydrogen Peroxide

A water-soluble catalyst based on a silicotungstate polyoxometalate, K₈[β-SiW₁₁O₃₉] · 14H₂O, was developed for the oxidation of pyridines and alcohols with hydrogen peroxide. The reactions were carried out in water, and good yields of the corresponding heterocyclic N-oxides and ketones were obtained under relatively mild conditions. The catalyst could be easily recovered by extraction with ethyl acetate and reused several times.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Nano–silica functionalized with thiol–based dendrimer as a host for gold nanoparticles: An efficient and reusable catalyst for chemoselective oxidation of alcohols

In this paper, we present the synthesis of Au nanoparticles supported on nanosilica thiol based dendrimer, nSTDP. The catalyst was prepared by reduction of HAuCl₄ with NaBH₄ in the presence of nSTDP. The resulting Au_np–nSTDP materials were characterized by FT–IR and UV–vis spectroscopic methods, SEM, TEM, TGA, XPS and ICP analyses. The characterization of the catalyst showed that Au nanoparticles with the size of 2–6 nm are homogeneously distributed on the nSTDP dendrimer with a catalyst loading of about 0.19 mmol/g of catalyst. The Au_np–nSTDP catalyst was used in the oxidation of alcohols with tert–butyl hydroperoxide (TBHP) as oxidant. The influence of vital reaction parameters such as solvent, oxidant and amount of catalyst on the oxidation of alcohols was investigated. These reactions were best performed in an acetonitrile/water mixture (3:2) in the presence of 0.76 mol% of the catalyst on the basis of the Au content at 80 °C under atmospheric pressure of air to afford the desired products in high yields (80–93% for benzyl alcohols). The Au_np–nSTDP catalyst exhibited a high selectivity toward the corresponding aldehyde and ketone (up to 100%). Reusabiliy and stability tests demonstrated that the Au_np–nSTDP catalyst can be recycled with a negligible loss of its activity. Also this catalytic exhibited a good chemoselectivity in the oxidation of alcohols.     

Aerobic oxidation of benzyl alcohols by MoVI compounds

Selective and controlled aerobic oxidation of activated benzyl alcohols to the corresponding aldehydes is achieved in refluxing CH₃CN using catalytic amounts of MoO₂Cl₂(L)₂ where L is DMSO, DMF or THF. The catalysis reactions are possible under open air in the absence of any other external co‐oxidants. However, bubbling of oxygen to the reaction mixture is useful in making the catalysis reaction sustained. Both activated and deactivated varieties of α‐substituted benzyl alcohols (secondary alcohols) give ketones in the same reaction conditions. The inexpensive catalyst is selective towards activated primary benzyl alcohols and also, being mild, stops the oxidation at the aldehyde stage, making it synthetically useful. Copyright © 2006 John Wiley & Sons, Ltd.