Selective oxidation of sulfides and olefins by a manganese(III) complex containing an N,O-type bidentate oxazine ligand

Di(hydroperoxy)adamantane adducts: synthesis, characterization and application as oxidizers for the direct esterification of aldehydes

The di(hydroperoxy)adamantane adducts of water (1) and phosphine oxides p-Tol₃PO·(HOO)₂C(C₉H₁₄) (2), o-Tol₃PO·(HOO)₂C(C₉H₁₄) (3), and Cy₃PO·(HOO)₂C(C₉H₁₄) (4), as well as a CH₂Cl₂ adduct of a phosphole oxide dimer (8), have been created and investigated by multinuclear NMR spectroscopy, and by Raman and IR spectroscopy. The single crystal X-ray structures for 1-4 and 8 are reported. The IR and ³¹P NMR data are in accordance with strong hydrogen bonding of the di(hydroperoxy)adamantane adducts. The Raman ν(O-O) stretching bands of 1-4 prove that the peroxo groups are present in the solids. Selected di(hydroperoxy)alkane adducts, in combination with AlCl₃ as catalyst, have been applied for the direct oxidative esterification of n-nonyl aldehyde, benzaldehyde, p-methylbenzaldehyde, p-bromobenzaldehyde, and o-hydroxybenzaldehyde to the corresponding methyl esters. The esterification takes place in an inert atmosphere, under anhydrous and oxygen-free conditions, within a time frame of 45 minutes to 5 hours at room temperature. Hereby, two oxygen atoms per adduct assembly are active with respect to the quantitative transformation of the aldehyde into the ester.

Ionic-liquid-modified CMK-3 as a support for the immobilization of molybdate ions (MoO42-): Heterogeneous nanocatalyst for selective oxidation of sulfides and benzylic alcohols

A nanometric carbon CMK-3 modified with octylimidazolium ionic liquid and MoO₄^2- as a new hybrid catalyst was synthesized. The study is the first to report a successful immobilization of MoO₄⁼ on the CMK-3/OctIm as a hybrid nanocatalyst. A variety of analytical methods were utilized to determine the properties of the structure and morphology of the synthesized nanocatalyst [CMK-3/Im/MoO₄^2-]. The analytical techniques were transmission electron microscopy (TEM), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP), X-ray diffraction (XRD), N₂ isotherms (BET), IR spectroscopy and thermogravimetric analysis (TGA). CMK-3/OctIm/MoO₄^2- hybrid catalyst demonstrated a considerable catalytic activity. It is a recyclable nanocatalyst that is utilized to chemoselectively oxidize different types of sulfides to the corresponding sulfoxides and benzylic alcohols to aldehydes using the green oxidant, hydrogen peroxide (H₂O₂) in high-yields. With a little leaching and variation in activity, it is possible to recover and reuse the catalyst frequently. A combination of molybdate anion and the CMK-3 order mesoporous carbon resulted in an improvement in the performance of catalysis and ease of separation for the reaction procedure.

Hydrogen peroxide adducts of triarylphosphine oxides

Five new hydrogen peroxide adducts of phosphine oxides (p-Tol₃PO·H₂O₂)₂ (1), (o-Tol₃PO·H₂O₂)₂ (2), (o-Tol₂PhPO·H₂O₂)₂ (3), (p-Tol₃PO)₂·H₂O₂ (4), and (o-TolPh₂PO)₂·H₂O₂ (5), and the water adduct (o-Tol₂PhPO·H₂O)₂ (6) have been synthesized and fully characterized. Their single crystal X-ray structures have been determined and analyzed. The IR and ³¹P NMR data are in accordance with strong hydrogen bonding of the hydrogen peroxide. The mono- versus dimeric nature of the adduct assemblies has been investigated by DOSY NMR experiments. Raman spectroscopy of the symmetric adducts and the ν(O-O) stretching bands confirm the presence of hydrogen-bonded hydrogen peroxide in the solid materials. The solubilities in organic solvents have been quantified. Due to the high solubilities of 1-6 in organic solvents their ¹⁷O NMR spectra could be recorded in natural abundance, providing well-resolved signals for the P[double bond, length as m-dash]O and O-O groups. The adducts 1-5 have been probed regarding their stability in solution at 105 °C. The decomposition of the adduct 1 takes place by loss of the active oxygen atoms in two steps.

Selective synthesis and stabilization of peroxides via phosphine oxides

MEKPO (methyl ethyl ketone peroxide) and other peroxides can be synthesized selectively and stabilized as hydrogen-bonded phosphine oxide adducts.

Nanoparticle supported, magnetically separable manganese porphyrin as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions

Magnetically separable manganese porphyrin was prepared by immobilizing on functionalized magnetic nanoparticles via the amino propyl linkage and used as an efficient retrievable nanocatalyst in hydrocarbon oxidation reactions.

Hydrogen Peroxide and Di(hydroperoxy)propane Adducts of Phosphine Oxides as Stoichiometric and Soluble Oxidizing Agents

Aqueous hydrogen peroxide is widely used as an oxidizing agent in industry and academia. Herein, the hydrogen peroxide adducts of phosphine oxides, [tBu3PO⋅H2O2]2 and [Ph3PO⋅H2O2]2⋅H2O2, are described. Additionally, the corresponding di(hydroperoxy)propane adducts R3PO⋅(HOO)2CMe2 (R=Cy, Ph) were synthesized and characterized. All adducts could be obtained as large single crystals suitable for structural characterization by X-ray crystallography and solid-state NMR spectroscopy. The di(hydroperoxy)propane adducts are soluble in organic solvents which enables oxidation reactions in one phase. As the adducts are solid and molecular, they can easily be applied stoichiometrically. No loss of oxidizing power occurs upon long-term storage of the single crystals at room temperature or the powders at -20 °C.

A novel iron complex containing an N,O-type bidentate oxazoline ligand: Synthesis, X-ray studies, DFT calculations and catalytic activity

A five-coordinated Fe(III) complex with the distorted trigonal bipyramidal configuration was synthesized by reactions of FeCl3⋅6H2O and 2-(2'-hydroxyphenyl)oxazoline (Hphox) as a bidentate ON donor oxazoline ligand. Complex [Fe(phox)2Cl] was fully characterized, including by single-crystal X-ray structure analysis. DFT calculations were accompanied with experimental results in order to obtain a deeper insight into the electronic structure and vibrational normal modes of complex. Oxidation of sulfides to sulfoxides in one-step was conducted by this complex as catalyst using urea hydrogen peroxide (UHP) in mixture of CH2Cl2/CH3OH (1:1) under air at room temperature. The results show that using this system in oxidation of sulfides, sulfoxides are obtained as the main products, together with variable amounts of sulfones (≤13%), depending on the nature of the substrate.