2461-34-9Relevant academic research and scientific papers
Synthesis, structural, spectroscopic, electrochemical, magnetic, and catalytic properties of the trinuclear MnIII TRIPLESALEN COMPLEX [(talen t- Bu 2){Mn(OAc)}3] exhibiting three salen-subunits in a β-cis-conformation
Krickemeyer, Erich,Kaiser, Yvonne,Stammler, Anja,Boegge, Hartmut,Glaser, Thorsten
, p. 1527 - 1533 (2013)
Reaction of the triplesalen ligand H6talen t-Bu 2 with three equivalents Mn(OAc)2·4H2O in MeOH results in the formation of a brown solid which upon recrystallization from CH3CN provides the trinuclear complex [(talen t-Bu 2){Mn(OAc)}3] ·7CH3CN as evidenced by single-crystal X-ray diffraction. The triple tetradentate ligand (talen t-Bu 2)6- coordinates to three MnIII ions in the rare β-cis-conformation of the salen-like ligand compartments with the central oxygen donor (Oc) being rotated out of the plane. This results in a longer Mn-Oc bond length of 2.00 A compared to the mean Mn-Ot bond lengths of the terminal phenolates at 1.86 A. The six-coordination is saturated by bidentate OAc- ligands. The electronic absorption spectrum measured in MeOH appears to be almost identical to all other complexes already studied possessing a {(talen t-Bu 2)MnIII3}3+ subunit (in the trans-conformation). The spectra measured in CH2Cl2 and CH3CN exhibit significant variations of the absorption features in the CT region above 20000 cm-1 and a low-energy shift of the d-d transitions from a shoulder around 18000 cm-1 in CH3OH to maxima around 13000 cm-1 in CH2Cl2 and CH 3CN. This indicates a physical dissolution of [(talen t-Bu 2){Mn(OAc)}3] in CH2Cl2 and CH3CN solutions without major structural rearrangements, while in MeOH solution a structural rearrangement to the preferred trans-conformation of the salen-like coordination compartments occurs loosing the bidentate coordination mode of the OAc- ligands. Electrochemical measurements reveal unresolved irreversible processes in the range 0.9-1.4 V vs. Fc+/Fc corresponding to oxidations of the MnIII-phenolate units, while irreversible reductive waves in the range -0.7-(-1.2) V vs. Fc+/Fc correspond to MnIII to MnII reductions. The analysis of the magnetic data reveals a weaker antiferromagnetic interaction of J = -0.067 cm-1 and a stronger zero-field splitting of D = -5.57 cm-1 in comparison to the complexes with {(talen t-Bu 2)MnIII 3}3+ subunits in the trans-conformation consistent with the longer Mn-Oc distances and the asymmetric coordination environment, respectively. The complex [(talen t-Bu 2){Mn(OAc)}3] catalyzes the epoxidation of 1, 2-dihydronaphthalene with iodosylbenzene with complete conversion at room temperature. Copyright
Peroxygenase-Catalysed Epoxidation of Styrene Derivatives in Neat Reaction Media
Alcalde, Miguel,Arends, Isabel W. C. E.,Hollmann, Frank,Paul, Caroline E.,Rauch, Marine C. R.,Tieves, Florian
, (2019/08/30)
Biocatalytic oxyfunctionalisation reactions are traditionally conducted in aqueous media limiting their production yield. Here we report the application of a peroxygenase in neat reaction conditions reaching product concentrations of up to 360 mM.
The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
, p. 14740 - 14749 (2016/11/18)
The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
Chemoenzymatic epoxidation of alkenes based on peracid formation by a Rhizomucor miehei lipase-catalyzed perhydrolysis reaction
Méndez-Sánchez, Daniel,Ríos-Lombardía, Nicolás,Gotor, Vicente,Gotor-Fernández, Vicente
, p. 1144 - 1148 (2014/02/14)
A chemoenzymatic and selective method for the epoxidation of a series of cyclic and linear alkenes is described. Epoxides have been obtained in moderate to excellent conversions under mild reaction conditions through a two-step sequence, carried out in one-pot. This chemoenzymatic approach is based on a Rhizomucor miehei lipase-catalyzed perhydrolysis reaction to form the corresponding peracid, and subsequent epoxidation of the corresponding alkenes. Reaction parameters with influence in the biotransformation have been optimized specially focusing in the efficient enzymatic peracid formation by means of the correct choice of solvent, oxidant, and peracid precursor. This chemoenzymatic approach has been efficiently applied for the first time, in the regioselective chemical oxidation of (S)-carvone and limonene, both showing an opposite behavior for the oxidation of the internal and external C-C double bond, respectively.
Ruthenium(IV) porphyrin catalyzed highly selective oxidation of internal alkenes into ketones with Cl2pyNO as terminal oxidant
Wang, Zhi-Ming,Sang, Xue-Ling,Che, Chi-Ming,Chen, Jian
, p. 1736 - 1739 (2014/03/21)
A new method for the conversion of internal alkenes into ketones without cleavage of CC bond by using dichlororuthenium(IV) meso-tetrakis(2,6- dichlorophenyl)porphyrin [RuIV(TDCPP)Cl2] as catalyst and 2,6-dichloropyridine N-oxide(Cl2pyNO) as oxidant is developed.
Mn(III) complexes with tridentate N,N,O-ligands as catalysts for the epoxidation of alkenes
Aghmiz,Mostfa,Iksi,Rivas,Gonzalez,Diaz,El Guemmout,El Laghdach,Echarri,Masdeu-Bulto
, p. 2567 - 2577 (2013/08/23)
Mn(III) complexes with tridentate Schiff bases have been prepared and applied as catalyst precursors in epoxidation of alkenes using iodosobenzene as an oxidant providing high conversions and high selectivities when cyclohexene derivatives were studied.
Biomimetic hydrocarbon oxidation catalyzed by nonheme iron(III) complexes with peracids: Evidence for an Fev=O species
Lee, Sun Hwa,Han, Jung Hee,Kwak, Han,Lee, Sung Jea,Lee, Eun Yong,Kim, Hee Jin,Lee, Jung Hwan,Bae, Cheolbeom,Lee, Soo No,Kim, Youngmee,Kim, Cheal
, p. 9393 - 9398 (2008/09/21)
Mononuclear nonheme iron-(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Fe(Me2bpb)Cl(H2O)] (3a) and [Fe(bpc)Cl(H2O)] (4a), were prepared by substitution reactions involving the previously synthesized iron(III) complexes [Et3NH] [Fe(Me2bpb)Cl2] (3) and [Et3NH][Fe(bpc)Cl 2] (4). Complexes 3 a and 4 a were characterized by IR and elemental analysis, and complex 3 a also by X-ray crystallography. Nonheme iron(III) complexes 3, 3a, 4, and 4 a catalyze olefin epoxidation and alcohol oxidation on treatment with mchloroperbenzoic acid. Pairwise comparisons of the reactivity of these complexes revealed that the nature of the axial ligand (Cl- versus H2O) influences the yield of oxidation products, whereas an electronic change in the supporting chelate ligand has little effect. Hydrocarbon oxidation by these catalysts was proposed to involve an iron(V) oxo species which is formed on heterolytic O-O bond cleavage of an iron acylperoxo intermediate (FeOO-C(O)R). Evidence for this iron(V) oxo species was derived from KIE (kH/kD) values, H218O exchange experiments, and the use of peroxyphenylacetic acid (PPAA) as the peracid. Our results suggest that an Fev=O moiety can form in a system wherein the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors. This work is relevant to the chemistry of mononuclear nonheme iron enzymes that are proposed to oxidize organic substrates via reaction pathways involving high-valent iron oxo species.
Synthesis and activity of macrocyclized chiral Mn(III)-Schiff-base epoxidation catalysts
Martinez, Alexandre,Hemmert, Catherine,Gornitzka, Heinz,Meunier, Bernard
, p. 2163 - 2171 (2007/10/03)
A series of chiral macrocyclic Mn(III)Salen complexes has been prepared with two salicylidene moieties linked in their 3 and 3′ positions by aliphatic polyether bridges of variable lengths or by a more rigid aromatic junction arm. X-ray structures of ligand precursors and of complex 8 have been performed. All complexes have been used in the asymmetric epoxidation of 1,2-dihydronaphthalene with NaOCl as oxygen atom donor and exhibited modest enantiomeric excesses. Complex 10 was selected to be tested with two cis-disubstituted olefins and several oxidants, namely NaOCl, PhIO and n-Bu 4NHSO5. 2,2′-Dimethylchromene oxide was obtained from 2,2′-dimethylchromene with ee values of 56% and 74% when using 10 and NaOCl and PhIO, respectively.
Cyclodextrins containing an acetone bridge. Synthesis and study as epoxidation catalysts
Rousseau, Cyril,Christensen, Brian,Petersen, Torben Ellebaek,Bols, Mikael
, p. 3476 - 3482 (2007/10/03)
Three cyclodextrine derivatives (6A,6 D-di-O-(prop-2-one-1,3-dienyl)-α-cyclodextrin (1), 6-O-(prop-2-one-1-yl)-α-cyclodextrin (2) and 6A,6 D-di-O-(prop-2-one-l, 3-dienyl)-β-cyclodextrin (3)) were synthesised and investigated as epoxidation catalysts. The three compounds were synthesised from the corresponding perbenzylated cyclodextrins which were mono- or didebenzylated in the 6-position using Sinay's method. Reaction with NaH and methallyl chloride in the case of 2, or methallyl dichloride in the case of 1 and 3, followed by dihydroxylation, periodate cleavage and protection group removal gave the target compounds. All three compounds catalysed, in the presence of oxone, the epoxidation of a series of alkenes. Epoxidation was compared to the reaction catalysed by simple ketones and inhibition was studied.
Ruthenium nanoparticles supported on hydroxyapatite as an efficient and recyclable catalyst for cis-dihydroxylation and oxidative cleavage of alkenes
Ho, Chi-Ming,Yu, Wing-Yiu,Che, Chi-Ming
, p. 3303 - 3307 (2007/10/03)
Impregnation of hydroxyapatite with colloidal ruthenium results in the formation of a catalyst that effects cis-dihydroxylation and oxidative cleavage of alkenes to their respective cis-1,2-diols and carbonyl products in good to excellent yields (see scheme). The supported ruthenium catalyst can be easily recycled and reused for consecutive reaction runs without significant deterioration of the catalytic activities. R1, R2 = H, alkyl, aryl.
