Peroxo Complexes of Molybdenum, Tungsten and Rhenium with Phase Transfer Active Ligands: Catalysts for the Oxidation of Olefins and Aromatics by Hydrogen Peroxide and Bistrimethylsilyl Peroxide

Jost, Carsten; Wahl, Günter; Kleinhenz, Dirk

doi:10.1002/3527600396.ch16

Cited by 10 publications

(6 citation statements)

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“…By considering these changes and also reported mechanisms for the epoxidation reactions in the presence of tungsten( vi ) coordination compounds, 25 a mechanism was proposed for this catalytic system (see Scheme 3 ). Similar to the reports in literature, 26 it is predictable that the oxido–peroxido-tungsten species formed by the interaction of hydrogen peroxide with compound 1 on the surface of the hydrogenised catalyst are active and responsible intermediates for epoxidation of olefins.…”

Section: Resultssupporting

confidence: 86%

Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound

et al. 2022

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Section: Resultssupporting

confidence: 86%

Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound

et al. 2022

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“…Stoichiometric toxic oxidants, such as chromium(VI) salts, cerium ammonium nitrate (CAN), thallium(III) nitrate, potassium permanganate (KMnO 4 ), potassium dichromate (K 2 Cr 2 O 7 ), and sulfuric acid/nitric acid (H 2 SO 4 /HNO 3 ), have been widely employed in the past . Recently, according to the green chemistry approach, they have been substituted by ecofriendly reagents, such as oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ), activated by an appropriate catalyst (iron and manganese porphyrins, phthalocyanines, iron amide complexes, TAML (Tetra-Amido Macrocyclic Ligand), selenoxides, polyoxometallates, titanium silicalite, tungsten, molybdenum and vanadium complexes, Sn-zeolite beta, and methyltrioxorhenium) …”

Section: Introductionmentioning

confidence: 99%

Chemoselective C-4 Aerobic Oxidation of Catechin Derivatives Catalyzed by the Trametes villosa Laccase/1-Hydroxybenzotriazole System: Synthetic and Mechanistic Aspects

Bernini

Crisante

Gentili³

et al. 2011

J. Org. Chem.

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Catechin derivatives were oxidized in air in the presence of the Trametes villosa laccase/1-hydroxybenzotriazole (HBT) system in buffered water/1,4-dioxane as reaction medium. The oxidation products, flavan-3,4-diols and the corresponding C-4 ketones, are bioactive compounds and useful intermediates for the hemisynthesis of proanthocyanidins, plant polyphenols which provide beneficial health properties for humans. Determinations of oxidation potentials excluded that catechin derivatives could be directly oxidized by laccase Cu(II), while it resulted in the H-abstraction from benzylic positions being promptly promoted by the enzyme in the presence of the mediator HBT, the parent species producing in situ the reactive intermediate benzotriazole-N-oxyl (BTNO) radical. A remarkable and unexpected result for the laccase/HBT oxidative system has been the chemoselective insertion of the oxygen atom into the C-4-H bond of catechin derivatives. Mechanistic aspects of the oxidation reaction have been investigated in detail for the first time in order to corroborate these results. Since the collected experimental findings could not alone provide information useful to clarify the origin of the observed chemoselectivity, these data were expressly supplemented with information derived by suitable molecular modeling investigations. The integrated evaluation of the dissociation energies of the C-H bonds calculated both by semiempirical and DFT methods and the differential activation energies of the process estimated by a molecular modeling approach suggested that the observed selective oxidation at the C-4 carbon has a kinetic origin.

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“…An interesting report involving the isolation and structure determination of complexes of the type [MoO(O 2 ) 2 (L 2 )] (L = long chain trialkylamine oxide, -phosphane oxide, and -arsane oxide) appeared, and they were found to be catalytically active (with moderate efficiency) with H 2 O 2 as an oxidant . Subsequently, it was found that even better epoxidation ability of the Mo and W oxoperoxo complexes could be achieved using the tri( n -dodecayl)-arsane oxide ligand under biphasic condition CHCl 3 /30% H 2 O 2 at 60 °C …”

Section: Introductionmentioning

confidence: 99%

Oxo- and Oxoperoxo-molybdenum(VI) Complexes with Aryl Hydroxamates: Synthesis, Structure, and Catalytic Uses in Highly Efficient, Selective, and Ecologically Benign Peroxidic Epoxidation of Olefins

et al. 2006

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A solution obtained by dissolving MoO3 in H2O2 reacts separately with secondary hydroxamic acids (viz., N-benzoyl N-phenyl hydroxamic acid (BPHAH), N-benzoyl N-ortho-, -meta-, -para-tolyl hydroxamic acids, (BOTHAH, BMTHAH, and BPTHAH, respectively), and N-cinnamoyl N-phenyl hydroxamic acid (CPHAH) affording [MoO(O2)(BPHA)2] (1), [MoO(O2)(BOTHA)2] (2), [MoO(O2)(BMTHA)2] (3), [MoO(O2)(BPTHA)2] (4), and [Mo(O)2(CPHA)2](5), respectively. The O and O2 are situated cis to each other in 2-4, but in each case, they are disordered and distributed over four sites. This disorder does not exist in the 6-coordinate cis dioxo complex 5, to which crude MoO(O2)(CPHA)2 (5') was converted during recrystallization. An aqueous molybdate solution readily reacts with all those hydroxamic acids producing [Mo(O)2(hydroxamate)2] (6). While 2, 3, and 4 possess a very distorted pentagonal bipyramidal structure, 5 has a distorted octahedral geometry. In the solid state, as well as in solution, 5 exists as two apparently enantiomerically related molecules differing in the orientation of the pendant phenyl rings. To emphasize that the formation and structural uniqueness of 5 compared to 1-4 is caused by the influence of the cinnamoyl residue, one compound of the 6 series, namely, [Mo(O)2(BPHA)2] (6A), was structurally characterized to prove directly that the special stereochemical properties of 5 rely on the special electronic structure of CPHA- ligand. Complexes 1-5, as well as 6, show high potential and selectivity as catalysts in the epoxidation of olefins at room temperature in the presence of NaHCO3 as a promoter and H2O2 as a terminal oxidant. A comparative epoxidation study has been performed to determine the relative efficiency of the catalysts. To make the epoxidation method cost effective, a study to optimize the use of H2O2 has also been performed. To obtain evidence in favor of our suggested mechanism to this homogeneous olefin --> epoxide conversion, it was necessary to synthesize a peroxo-rich compound, namely, [MoO(O2)2BMTHA]- (7), but the attempted synthesis culminated in the isolation of [MoO(O2)2(C6H5COO)]- (8), obviously, via the hydrolysis of coordinated BMTHA.

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Peroxo Complexes of Molybdenum, Tungsten and Rhenium with Phase Transfer Active Ligands: Catalysts for the Oxidation of Olefins and Aromatics by Hydrogen Peroxide and Bistrimethylsilyl Peroxide

Cited by 10 publications

References 0 publications

Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound

Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound

Chemoselective C-4 Aerobic Oxidation of Catechin Derivatives Catalyzed by the Trametes villosa Laccase/1-Hydroxybenzotriazole System: Synthetic and Mechanistic Aspects

Oxo- and Oxoperoxo-molybdenum(VI) Complexes with Aryl Hydroxamates: Synthesis, Structure, and Catalytic Uses in Highly Efficient, Selective, and Ecologically Benign Peroxidic Epoxidation of Olefins

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