Aqueous Tert-butyl Hydroperoxide Research Articles

Synthesis, spectral characterization, SC-XRD, HSA, DFT and catalytic activity of a dioxidomolybdenum complex with aminosalicyl-hydrazone Schiff base ligand: An experimental and theoretical approach

A new dioxidomolybdenum(VI) complex has been successfully prepared by the reaction of an ONO donor Schiff base, derived by condensing 4-amino-2-hydroxybenzohydrazide and 3-methoxysalicylaldehyde, with MoO2(acac)2. The structures of synthesized products were explored spectroscopically through FT-IR, 1H &13C NMR and by elemental composition (CHN) through combustion analysis. The structural investigations of the dioxidomolybdenum(VI) complex were accomplished by taking its diffraction data through X-ray crystallography. The tridentate Schiff base ligand is bonded to the central metal through its deprotonated enolic and phenolic oxygen atoms and by the nitrogen of the azomethine group. The interpretation of the data obtained through diffraction analysis validates the distorted octahedral geometry of the prepared metal complex. QTAIM, MEP and NCI calculations and Hirshfeld surface analysis were performed to investigate the nature and types of non-covalent linkages present among the sample molecules. The theoretical calculations, performed by DFT using the B3LYP/Def2-TZVP level of theory, direct that the intended outcomes are in compliance with the actual consequences. Furthermore, the catalytic potential of the molybdenum complex was explored for the selective oxidation of benzylic alcohols to the desirable aryl aldehydes at room temperature in the presence of 70% aqueous tert-butyl hydroperoxide (TBHP) under solvent-free conditions. The main advantage of the present catalytic work is the accomplishment of reaction in a short period of time, high percentage yield and easy work-out procedure.

Formation of Tetrahydrofurano-, Aryltetralin, and Butyrolactone Norlignans through the Epoxidation of 9-Norlignans

Epoxidation of the C=C double bond in unsaturated norlignans derived from hydroxymatairesinol was studied. The intermediate epoxides were formed in up to quantitative conversions and were readily further transformed into tetrahydrofuran, aryltetralin, and butyrolactone products—in diastereomeric mixtures—through ring-closing reactions and intramolecular couplings. For epoxidation, the classical Prilezhaev reaction, using stoichiometric amounts of meta-chloroperbenzoic acid (mCPBA), was used. As an alternative method, a catalytic system using dimeric molybdenum-complexes [MoO2L]2 with ONO- or ONS-tridentate Schiff base ligands and aqueous tert-butyl hydroperoxide (TBHP) as oxidant was used on the same substrates. Although the epoxidation was quantitative when using the Mo-catalysts, the higher temperatures led to more side-products and lower yields. Kinetic studies were also performed on the Mo-catalyzed reactions.

Aqueous tert-Butyl Hydroperoxide Mediated Regioselective Ring-Opening Reactions of Spiro-aziridine-epoxy Oxindoles: Synthesis of 3-Peroxy-3-substituted Oxindoles and Their Acid-Mediated Rearrangement.

A highly efficient regioselective C3-peroxylation of spiro-aziridine and spiro-epoxy oxindoles has been developed with commercially available 70% aqueous tert-butyl hydroperoxide under solvent-free and metal/catalyst-free conditions. The protocol provides an easy access of 3-peroxyoxindoles, which undergo acid-mediated rearrangement to afford unprecedented 2-hydroxy-2-substituted-2H-benzo[b][1,4]oxazin-3(4H)-ones. The protocol is also equally effective for the ring opening of simple phenyl aziridine with excellent regio-selectivity.

Metal-Free Oxidative Coupling of Tetrahydroisoquinolines and 3-Fluorooxindoles on Water

An efficient, metal-free oxidative coupling of tetrahydroisoquinolines and 3-fluorooxindoles on water has been developed. Using aqueous tert-butyl hydroperoxide as the oxidant, Et3N as the base, and water as the sole solvent, a variety of 3-fluorooxindoles fully substituted at the 3-position and containing a tetrahydroisoquinoline fragment has been successfully prepared in yields of up to 93% with an anti/syn stereo­selectivity of up to 99:1 under very mild and safe reaction conditions.

CuO-catalyzed oxidation of aryl acetates with aqueous tert-butyl hydroperoxide for the synthesis of α-ketoesters

A practical method to access α-ketoesters from readily available aryl acetates is developed. In this approach, aqueous tert-butyl hydroperoxide and CuO are employed. No additional solvents are required and it was found that the peroxide side products in the reaction can be decomposed by pyridine.

Two cis-Dioxomolybdenum(VI) Complexes with Tridentate ONO Aroylhydrazone Schiff Bases: Syntheses, Characterization, Crystal Structures, and Catalytic Epoxidation Property

Two new cis-dioxomolybdenum(VI) complexes, [MoO2(L1)MeOH] (I) and [MoO2(L2)MeOH] (II) with potentially tridentate ONO aroylhydrazone Schiff bases derived from 3-methoxysalicylaldehyde with 4-bromobenzohydrazide and 4-trifluoromethylbenzohydrazide, respectively, have been synthesized and fully characterized on the basis of elemental analysis, FT-IR, molar conductivity, and electronic spectra. Structures of the complexes have been accomplished by single crystal X-ray diffraction (СIF files CCDC nos. 1433352 (I) and 1433318 (II)). The complexes have distorted octahedral structures in which the aroylhydrazones behave as binegative ligands. It is also revealed from the crystal structures that the Mo(VI) center adopts NO5 donor environment, and the octahedral coordination is furnished by two oxido groups and oxygen atoms of methanol or deprotonated methanol molecules. The catalytic properties were investigated for epoxidation of cyclooctene using aqueous tert-butyl hydroperoxide as the oxidant.

One-pot synthesis of amides via the oxidative amidation of aldehydes and amines catalyzed by a copper-MOF.

An efficient method for the oxidative amidation of aldehydes with primary aromatic and aliphatic amines has been developed for the synthesis of a wide variety of amides using inexpensive Cu2(BDC)2DABCO (Cu-metal–organic framework [MOF]) as a recyclable heterogeneous catalyst, and N-chlorosuccinimide and aqueous tert-butyl hydroperoxide as oxidants in acetonitrile. This amidation reaction is operationally straightforward and provides secondary amides in good yields in most cases, utilizing inexpensive and readily available reagents under mild conditions.

Dimeric copper(II) tetracarboxylates as catalysts in the selective epoxidation of styrene

Dicopper(II) tetracarboxylate complexes of the type [Cu2(µ-O2CR)4L2] have received a great deal of attention from inorganic chemists in the past. However, these well-known species have been rarely studied as catalysts. Herein we describe the synthesis, UV–Vis spectral behavior and catalytic properties of six species of this type, viz. [Cu2(µ-O2CC6H5)4(py)2] (I), [Cu2(µ-O2CC6H5)4(4-CNpy)2] (II), [Cu2(µ-O2CC6H5)4(3-CNpy)2] (III), [Cu2(µ-O2CCH3)4(py)2] (IV), [Cu2(µ-O2CC7H15)4(4-CNpy)2] (V) and [Cu2(µ-O2CC7H15)4(3-CNpy)2] (VI). As evidenced by their solid state and solution UV–Vis spectra, these complexes retain their dinuclear integrity in solution and therefore they have been investigated as homogenous catalysts for styrene epoxidation. They exhibit very good to excellent catalytic activities towards the oxidation of styrene with aqueous tert-butylhydroperoxide (TBHP) as the terminal oxidant. The reactions give styrene oxide (SO) and benzaldehyde (Bzal) as products in varying proportions, but with good selectivity for SO. Under optimized conditions, a maximum of 82% selectivity towards SO is obtained at 78% styrene conversion catalyzed by I at room temperature.

The mononuclear MoO2 2+ complexes with stereochemically rigid 4-aminobenzhydrazide based ligands

A range of dioxidomolybdenum(VI) complexes has displayed very high catalytic activities and exquisite selectivity. The dioxidomolybdenum(VI) mononuclear complexes with 4-aminobenzoylhydrazone ligands (salicylaldehyde (H2L1), 3- methoxysalicylaldehyde (H2L2), or 4- methoxysalicylaldehyde 4-aminobenzoylhydrazone (H2L3) being of the type cis-[MoO2L1-3(D)] ; D = MeOH, EtOH, H2O, dmf] have been prepared and structurally characterized. The crystal structure analysis of mononuclear complexes (Fig.1.) reveals distorted octahedral Mo(VI) coordination by ONO donor atoms from dianionic tridentate 4- aminobenzoylhydrazone ligands, two oxido oxygen atoms from the MoO22+ moiety and the oxygen atom from coordinated alcohol molecules (D = MeOH, EtOH).The molybdenum oxido groups of the MoO22+ moiety show the expected mutual cis configuration and are located trans to the imine nitrogen atom and coordinated alcohol molecule. The bond distances range around Mo follows trend: Mo-Ot < Mo-O(phenolate) < Mo- O(hydrazone part) < Mo-N< MoO(ROH ; R=Me, Et). The bicyclic system of two chelate rings is slightly folded along the axis of molybdenum- imino bond and by the offset of metal centre apart from chelate planes towards the terminal oxygen atom. The most deviation from chelate rings coplanarity is shown by the phenolate oxygen atom due to its participation in intermolecular interactions. The complexes were tested for catalytic epoxidation of cyclooctene under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide (TBHP) as an oxidant. Due to trans effect of oxido oxygen atom, Mo-O(D) bond is the longest bond distance within molybdenum coordination sphere and it expected to be the point of maximum catalytic reactivity of the complexes. It is previously shown that pentacoordinated molybdenum systems activate oxidizing agent TBHP through adduct formation assisted by the O–H…O hydrogen bond. Another explanation of the substituent influence is p-π conjunctive effect with methoxy group due to increasing electron density of the phenyl ring.

Pd-Catalyzed Oxidation of Aldimines to Amides

Methods for the synthesis of amides via the direct oxidation of imines are rarely reported. Here we report an efficient method for Pd-catalyzed oxidation of imines to amide derivatives by the use of cheap aqueous tert-butyl hydroperoxide as an oxidant through a Wacker-type reaction. This method is practically convenient and displays high functional group tolerance, allowing a variety of imines to transform into the corresponding amide derivatives in moderate to good yields.

Synthesis of N-Sulfonylformamidines by tert-butyl Hydroperoxide–Promoted, metal-free, direct oxidative dehydrogenation of aliphatic amines

A direct and convenient metal-free method to prepare sulfonyl amidines in the presence of aqueous tert-butyl hydroperoxide (T-HYDRO) has been developed. Different tertiary and secondary amines were tested for compatibility with the oxidative conditions and could be coupled with sulfonyl azides to form the corresponding amidines in moderate to good yields.

Partial Isobutane Oxidation to tert‐Butyl Hydroperoxide in a Micro Reactor – Comparison of DTBP and Aqueous TBHP as Initiator

AbstractThe oxidation of isobutane has been investigated for the first time in a micro reactor for a wide range of process conditions comparing the product ratios obtained with di‐tert‐butyl peroxide (DTBP) and tert‐butyl hydroperoxide (TBHP) as initiator. DTBP led to nearly the double conversion compared to the same concentration of TBHP, but the selectivity of TBHP using TBHP as initiator was higher. Using aqueous TBHP, the conversions reached up to 6 % in case of supercritical conditions but stayed below 2 % in case of two‐phase flow experiments. With TBHP in decane as initiator a high conversion was reached but nearly no TBHP was formed. It seems that the silicon layer of the micro reactor was not stable under such experimental conditions. In the present work, for the first time a conversion level near to that of the industrial batch process has been reached in a micro reactor for the isobutane oxidation.

TBHP/n-Bu4PBr-Promoted Oxidative Cross-Dehydrogenative Coupling of Aryl Methanols: A Facile Synthesis of Symmetrical Carboxylic Anhydride Derivatives

A transition-metal-free oxidative cross-dehydrogenative coupling reaction has been developed for the preparation of symmetrical carboxylic anhydrides through self-coupling dual C–O bond formations of aryl methanols. In the presence of a catalytic amount of tetrabutylphosphonium bromide (TBPB) as transfer agent and aqueous tert-butyl hydroperoxide (TBHP) as oxidant and reactant, methylene groups of aryl methanols were efficiently oxidized to C=O and coupled with the peroxide oxygen from TBHP to form a diverse array of symmetrical carboxylic anhydride derivatives.

Organocatalyzed oxidation of benzyl alcohols by a tetrazole-amino-saccharin: A combined experimental and theoretical (DFT) study

A new catalytic system for the anaerobic oxidation of benzyl alcohols using a tetrazole-amino-saccharin organocatalyst has been established. In a solvent-free and microwave assisted process comprising aqueous tert-butyl hydroperoxide (TBHP) as oxidant, a variety of benzyl alcohols has been efficiently converted to aldehydes under mild conditions. Most reactions are complete within 30min and the catalyst exhibits varied functional group compatibility. A catalytic cycle for the oxidation of the alcohols promoted by the tetrazole-amino-saccharin derivative is outlined involving radical species. DFT calculations performed for the oxidation of benzyl alcohol with and without organocatalyst show that the rate limiting step of the whole reaction is the cleavage of the OO bond in TBHP with the subsequent hydrogen abstraction from the alcohol. The tetrazole-amino-saccharin organocatalyst assists the H-abstraction from benzyl alcohol by the bound HO radical. The simplicity, selectivity and softness of reaction conditions of the studied organocatalytic protocol suggest a great potential for extensive use in synthetic chemistry.

Iodine-Catalyzed C-N Bond Formation: Synthesis of 3-Aminoquinoxalinones under Ambient Conditions.

A metal-free cross-dehydrogenative coupling between quinoxalinones (sp2 C-H) and amines (N-H) in the presence of catalytic iodine is reported. The reaction yields 3-aminoquinoxalinones in moderate to high yields under ambient conditions in dioxane as solvent and aqueous tert-butyl hydroperoxide (TBHP) as the terminal oxidant. The reaction is highly versatile and exhibits good functional group tolerance with a range of primary and secondary amines. It provides a practical access to pharmaceutically active 3-aminoquinoxalinone derivatives. Preliminary mechanistic studies reveal in situ iodination of the amine as the putative mode of activation.

Two-step conversion of carboxylic esters into distally fluorinated ketones via ring cleavage of cyclopropanol intermediates: application of sulfinate salts as fluoroalkylating reagents.

Tertiary cyclopropanols easily available from carboxylic esters have been used in the synthesis of distally fluorinated ketones. Cyclopropane ring cleavage reactions in methanol with aqueous tert-butyl hydroperoxide in the presence of a copper(ii) acetate catalyst and sodium triflinate (Langlois reagent) afford β-trifluoromethyl ketones in 16-74% isolated yields. Sodium triflinate serves as a precursor of reactive trifluoromethyl copper species, enabling ring-opening trifluoromethylation, as evidenced by mechanistic studies. We also demonstrate here that other sulfinate salts, such as sodium 1,1-difluoroethanesulfinate, sodium 2-(4-bromophenyl)-1,1-difluoroethanesulfinate and sodium 1-(trifluoromethyl)cyclopropanesulfinate, can be used as fluoroalkylation reagents, resulting in the corresponding fluorinated ketones.

Synthesis of a polymer–ruthenium complex Ru(pbbp)(pydic) and its catalysis in the oxidation of secondary alcohols with TBHP as oxidant

A polymer–ruthenium complex Ru(pbbp)(pydic) was synthesized from the reaction of poly-2,6-bis(benzimidazolyl)pyridine (pbbp) with RuCl3 and disodium pyridine-2,6-dicarboxylate (pydic). The Ru(pbbp)(pydic) was characterized thoroughly by spectroscopic methods. ICP analysis revealed that the percentage of complexation of 2,6-bis(benzimidazolyl)pyridine unit in pbbp was about 83%. The complex was tested as a heterogeneous catalyst for the oxidation of secondary alcohols to their corresponding carbonyl compounds in solvent-free conditions using aqueous tert-butyl hydroperoxide as oxidant. The developed catalytic system exhibited high activity and broad functional group compatibility, allowing a variety of secondary alcohols, including substituted secondary benzylic alcohols and secondary aliphatic ones, to be oxidized to the corresponding ketones in high yields. This Ru(pbbp)(pydic) could be recycled for several times, but it dissolved in part in the reaction mixture during the catalytic run leading to gradual deactivation of the catalyst with repeated runs.

O-Acetyl-Substituted Phenol Ester Synthesis via Direct Oxidative Esterification Utilizing Ethers as an Acylating Source with Cu2(dhtp) Metal–Organic Framework as a Recyclable Catalyst

A metal–organic framework (MOF) Cu2(dhtp) was prepared and used as a recyclable catalyst for the direct C–O coupling of ethers with 2-acylphenols to generate phenol esters. The Cu2(dhtp) displayed better efficiency in the production of phenol esters than several MOFs, as well as traditional homogeneous catalysts. The oxidant played an important role for the conversion, and aqueous tert-butyl hydroperoxide was the best choice. Heterogeneous catalysis was confirmed for the transformation, and no phenol ester generated by leached species, if any, was recorded. It was possible to reuse the Cu2(dhtp) catalyst numerous times in the conversion of 2-acylphenols and ethers to phenol esters without a noticeable deterioration in catalytic efficiency. To our best understanding, the direct esterification to produce phenol esters utilizing ethers as an acylating source assisted by solid catalysts has not been previously reported in the literature.

Characterization on thermal decompositions of tert-butyl hydroperoxide (TBHP) by confinement test

Thermal decomposition of 20 mass% aqueous tert-butyl hydroperoxide (TBHP) is performed by confined apparatus as a model reaction. Inductive effects are verified by of hydroxyl and tert-butoxy radicals produced by the thermolysis of H2O2 and di-tert-butyl peroxide (DTBP), respectively. Solvent effects are performed by 20 mass% TBHP in acetone, n-butyl alcohol, decane, nonane, Nujol, toluene and H2O. Thermodynamic and kinetic features, such as exothermic onset temperature, adiabatic temperature rise, maximum self-heat rate, maximum pressure and maximum temperature, are thus measured and utilized to characterize these mentioned influences. Hydroxyl radical is firstly discovered to possess the highest inductive effect on decomposition of TBHP. Exothermic onset temperature of 20 mass% aqueous TBHP is lowered from 146.0 ± 1.0 to 138.0 ± 2.0, 133.0 ± 0.0, 97 ± 8.8 and 89 °C by adding 10 mass% DTBP, 20 mass% DTBP, 10 mass% H2O2 and 20 mass% H2O2 relative to the mass of TBHP, respectively. The ranking of solvent effects on the thermal stability of solvated TBHP identified by exothermic onset temperature is arranged from high to low in the following: TBHP in toluene (178.5 ± 1.5 °C) > TBHP in decane (151.0 ± 2.0 °C) > TBHP in H2O (146.0 ± 1.0 °C) > TBHP in nonane (143.5 ± 2.5 °C) > TBHP in Nujol (138.5 ± 0.5 °C) > TBHP in acetone (128.0 ± 2.0 °C) > TBHP in n-BuOH (122.5 ± 3.5 °C).

Copper(II) and cobalt(II) tetrazole-saccharinate complexes as effective catalysts for oxidation of secondary alcohols

Mononuclear Cu(II) and Co(II) complexes comprising 2-methyltetrazole-saccharinate bidentate N,N-chelating ligand have been synthesized for the first time and tested as homogeneous catalysts for oxidation of secondary alcohols in a solvent-free and microwave assisted protocol using aqueous tert-butyl hydroperoxide (TBHP) as oxidant. The developed catalytic system exhibits broad functional group compatibility, allowing efficient and selective conversion of a variety of secondary alcohols, including allylic ones, into the corresponding ketones. With typical 0.2mol% content of the catalyst and under 20–50W microwave irradiation, most reactions are complete within 10min, presenting TONs up to 5.5×102 and TOFs up to 1.1×104h−1. No additives and co-oxidants have been used, while TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) acts as inhibitor in most cases. A plausible reaction mechanism involving the new catalytic systems is outlined.