Effective oxidation of benzylic and aliphatic alcohols with hydrogen peroxide catalyzed by a manganese(III) Schiff-base complex under solvent-free conditions

Aroylhydrazone Schiff Base Derived Cu(II) and V(V) Complexes: Efficient Catalysts towards Neat Microwave-Assisted Oxidation of Alcohols

A new hexa-nuclear Cu(II) complex [Cu3(μ2-1κNO2,2κNO2-L)(μ-Cl)2(Cl)(MeOH)(DMF)2]2 (1), where H4L = N'1,N'2-bis(2-hydroxybenzylidene)oxalohydrazide, was synthesized and fully characterized by IR spectroscopy, ESI-MS, elemental analysis, and single crystal X-ray diffraction. Complex 1 and the dinuclear oxidovanadium(V) one [{VO(OEt)(EtOH)}2(1κNO2,2κNO2-L)]·2H2O (2) were used as catalyst precursors for the neat oxidation of primary (cinnamyl alcohol) and secondary (1-phenyl ethanol, benzhydrol) benzyl alcohols and of the secondary aliphatic alcohol cyclohexanol, under microwave irradiation using tert-butyl hydroperoxide (TBHP) as oxidant. Oxidations proceed via radical mechanisms. The copper(II) compound 1 exhibited higher catalytic activity than the vanadium(V) complex 2 for all the tested alcohol substrates. The highest conversion was found for 1-phenylethanol, yielding 95.3% of acetophenone in the presence of 1 and in solvent and promoter-free conditions. This new Cu(II) complex was found to exhibit higher activity under milder reaction conditions than the reported aroylhydrazone Cu(II) analogues.

Cu(II) and Fe(III) Complexes Derived from N-Acetylpyrazine-2-Carbohydrazide as Efficient Catalysts Towards Neat Microwave Assisted Oxidation of Alcohols

The mononuclear Cu(II) complex [Cu((kNN′O-HL)(H2O)2] (1) was synthesized using N-acetylpyrazine-2-carbohydrazide (H2L) and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray crystallography. Two Fe(III) complexes derived from the same ligand viz, mononuclear [Fe((kNN′O-HL)Cl2] (2) and the binuclear [Fe(kNN′O-HL)Cl(μ-OMe)]2 (3) (synthesized as reported earlier), were also used in this study. The catalytic activity of these three complexes (1–3) was examined towards the oxidation of alcohols using tert-butyl hydroperoxide (TBHP) as oxidising agent under solvent-free microwave irradiation conditions. Primary and secondary benzyl alcohols (benzyl alcohol and 1-phenylethanol), and secondary aliphatic alcohols (cyclohexanol) were used as model substrates for this study. A comparison of their catalytic efficiency was performed. Complex 1 exhibited the highest activity in the presence of TEMPO as promoter for the oxidation of 1-phenylethanol with a maximum yield of 91.3% of acetophenone.

A H2O2/HBr system - several directions but one choice: oxidation-bromination of secondary alcohols into mono- or dibromo ketones

In this work we found that a H2O2-HBr(aq) system allows synthesis of α-monobromo ketones and α,α'-dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment, multifaceted reactivity, and compliance with green chemistry principles make the application of the H2O2-HBr(aq) system very attractive in laboratories and industry. The proposed oxidation-bromination process is selective in spite of known properties of ketones to be oxidized by the Baeyer-Villiger reaction or peroxidated with the formation of compounds with the O-O moiety in the presence of hydrogen peroxide and Bronsted acids.

Ruthenium carbonyl complexes with pyridylalkanol ligands: synthesis, characterization and catalytic properties for aerobic oxidation of secondary alcohols

Several new trinuclear ruthenium carbonyl complexes were synthesized and their application in aerobic oxidation of secondary alcohols was also established.

Color conversion of the magnetically separable Al/Fe oxide RNGO in the selective oxidation of benzyl alcohol induced the observation of its morphology change

The morphology changed in accordance with the catalytic performance through the observation of color variation during the lifetime test: with a chaotic layout and a comparable inferior catalytic activity initially, while a waffle or pastry state and a relatively superior activity in the prime time performance.

Mn(ii) acetate: an efficient and versatile oxidation catalyst for alcohols

A homogeneous catalytic system consisting of Mn(ii) acetate, tert-butylhydroperoxide, acetonitrile and trifluoroacetic acid oxidises various alcohols efficiently and selectively.

Oxidation of primary and secondary benzylic alcohols with hydrogen peroxide and tert-butyl hydroperoxide catalyzed by a “helmet” phthalocyaninato iron complex in the absence of added organic solvent

A “helmet” metallophthalocyanine of iron(iii) is a very effective catalyst for benzylic alcohol oxidation in the absence of added organic solvent.

Highly efficient Cu(I)-catalyzed oxidation of alcohols to ketones and aldehydes with diaziridinone

A novel and efficient Cu(I)-catalyzed oxidation of alcohols has been achieved with di-tert-butyldiaziridinone as the oxidant under mild conditions. A wide variety of primary and secondary alcohols with various functional groups can be oxidized to aldehydes and ketones in high yields. The reaction proceeds under neutral conditions making it compatible with acid- or base-sensitive substrates, and it is amenable to gram scale.

A Green and Efficient Oxidation of Alcohols by Amphiphilic Resin-Supported Gold Nanoparticles in Aqueous H2O2

A green and highly efficient oxidation of alcohols in aqueous H2O2 using amphiphilic resin (PS-PEG-NH2)-supported gold nanoparticles is described. The reaction proceeded with excellent yields and selectivities, in particular, for non-activated alcohols without base. The catalyst, in addition, could be readily recovered by simple work-up and reused several times without significant loss of its catalytic activity.

Mechanism of the enantioselective oxidation of racemic secondary alcohols catalyzed by chiral Mn(III)-salen complexes

The experiments described here clarify the mechanism and origin of the enantioselectivity of the oxidation of racemic secondary alcohols catalyzed by chiral Mn(III)-salen complexes using HOBr, Br(2)/H(2)O/KOAc or PhI(OAc)(2)/H(2)O/KBr as a stoichiometric oxidant. Key points of the proposed pathway include (1) the formation of a Mn(V)-salen dibromide, (2) its subsequent reaction with the alcohol to give an alkoxy-Mn(V) species, and (3) carbonyl-forming elimination to produce the ketone via a highly organized transition state with intramolecular transfer of hydrogen from carbon to an oxygen of the salen ligand.

Effective oxidation of sulfides to sulfoxides with hydrogen peroxide under transition-metal-free conditions

A "green" highly selective oxidation of organic sulfides to the corresponding sulfoxides was developed using hydrogen peroxide and glacial acetic acid under transition metal-free and mild conditions. The oxidation procedure is very simple and the products are easily isolated in excellent yields (90-99%).