1855-09-0Relevant articles and documents
Methyltrioxorhenium catalysed epoxidations: A comparative study of different N-donor ligands
Altmann, Philipp,Kühn, Fritz E.
, p. 4032 - 4035 (2009)
This report presents a comparative study on the influence of various N-donor ligands coordinated to methyltrioxorhenium (MTO) on the catalytic activity of olefin epoxidation. A monodentate (4-tert-butylpyridine), a bidentate (4,4′-dimethyl-2,2′-bipyridine) and a Schiff-base ligand were chosen for the coordination to MTO. This report is supposed to act as a benchmark for past and future results in this type of catalysis. Until now, unfortunately, the results are often difficult to compare due to varying sets of reaction conditions. In the present examination, identical reaction conditions were applied to find the optimum in performance. Accordingly, (i) ligand concentration, (ii) reaction temperature, (iii) catalyst concentration, (iv) olefin and (v) the solvent were varied. For labile olefins such as trans-β-methylstyrene, both the monodentate and the bidentate pyridine derivates show very good selectivities and activities with a MTO/ligand ratio of 1:5 at 25 °C. The Schiff-base is only a useful additive for the epoxidation of cyclooctene. Due to phase transfer effects it is difficult to compare two-phase systems (solvent dichloromethane (DCM)) to one-phase systems (solvent tert-butanol). A correlation between rotation speed of the stirrer and the turnover frequency was observed.
Different enantioselectivity and regioselectivity of the cytosolic and microsomal epoxide hydrolase catalyzed hydrolysis of simple phenyl substituted epoxides
Bellucci, Giuseppe,Chiappe, Cinzia,Cordoni, Antonio,Marioni, Franco
, p. 4219 - 4222 (1994)
The cytosolic (cEH) and the microsomal epoxide hydrolase (mEH) hydrolyse styrene oxide and trans-1-phenylpropene oxide with different enantioselectivity and regioselectivity. While mEH always leads to a regiospecific and enantioselective opening at the non-benzylic oxirane carbon, cEH gives a non-regioselective and non-enantioselective attack to styrene oxide and a regiospecific and non-enantioselective attack at the benzylic carbon of 1-phenylpropene oxide.
Asymmetric dihydroxylation using heterogenized cinchona alkaloid ligands on mesoporous silica
Lee, Hong Myung,Kim, Sang-Wook,Hyeon, Taeghwan,Kim, B. Moon
, p. 1537 - 1541 (2001)
Cinchona alkaloids have been successfully grafted on mesoporous silica. Asymmetric dihydroxylation using the heterogenized chiral ligands proceeded with varying degrees of enantioselection depending upon the nature of the chiral ligands. High asymmetric induction (up to >99.5% enantiomeric excess) almost equal to that obtained from the homogeneous catalyst system could be achieved using a dimeric alkaloid ligand with a six-carbon link between the ligand and the support (L3), while inferior results were obtained when a monomeric alkaloid ligand system was used. Reduced enantioselectivities were observed upon repeated recycling of the immobilized ligand system.
Oxidative carbon-carbon bond cleavage of 1,2-diols to carboxylic acids/ketones by an inorganic-ligand supported iron catalyst
Chen, Weiming,Xie, Xin,Zhang, Jian,Qu, Jian,Luo, Can,Lai, Yaozhu,Jiang, Feng,Yu, Han,Wei, Yongge
supporting information, p. 9140 - 9146 (2021/11/23)
The carbon-carbon bond cleavage of 1,2-diols is an important chemical transformation. Although traditional stoichiometric and catalytic oxidation methods have been widely used for this transformation, an efficient and valuable method should be further explored from the views of reusable catalysts, less waste, and convenient procedures. Herein an inorganic-ligand supported iron catalyst (NH4)3[FeMo6O18(OH)6]·7H2O was described as a heterogeneous molecular catalyst in acetic acid for this transformation in which hydrogen peroxide was used as the terminal oxidant. Under the optimized reaction conditions, carbon-carbon bond cleavage of 1,2-diols could be achieved in almost all cases and carboxylic acids or ketones could be afforded with a high conversion rate and high selectivity. Furthermore, the catalytic system was used efficiently to degrade renewable biomass oleic acid. Mechanistic insights based on the observation of the possible intermediates and control experiments are presented.
Photo-Induced Dihydroxylation of Alkenes with Diacetyl, Oxygen, and Water
Masuda, Yusuke,Ikeshita, Daichi,Murakami, Masahiro
, (2021/02/09)
Herein reported is a photo-induced production of vicinal diols from alkenes under mild reaction conditions. The present dihydroxylation method using diacetyl (= butane-2,3-dione), oxygen, and water dispenses with toxic reagents and intractable waste generation.
Nitrogen Dioxide Catalyzed Aerobic Oxidative Cleavage of C(OH)–C Bonds of Secondary Alcohols to Produce Acids
Liu, Mingyang,Zhang, Zhanrong,Song, Jinliang,Liu, Shuaishuai,Liu, Huizhen,Han, Buxing
supporting information, p. 17393 - 17398 (2019/11/11)
Stable organic nitroxyl radicals are an important class of catalysts for oxidation reactions, but their wide applications are hindered by their steric hinderance, high cost, complex operation, and separation procedures. Herein, NO2 in DMSO is shown to effectively catalyze the aerobic oxidative cleavage of C(OH)?C bonds to form a carboxylic group, and NO2 was generated in situ by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted into acids in excellent yields in this transition-metal-free system without any additives. Preliminary results also indicate its applicability to depolymerize recalcitrant macromolecular lignin. Detail studies revealed that NO2 from nitrates promoted the reaction, and NO2 served as hydrogen acceptor and radical initiator for the tandem oxidative reaction.
Regioselective 1,2-Diol Rearrangement by Controlling the Loading of BF3·Et2O and Its Application to the Synthesis of Related Nor-Sesquiterene- and Sesquiterene-Type Marine Natural Products
Wang, Jun-Li,Li, Hui-Jing,Wang, Hong-Shuang,Wu, Yan-Chao
supporting information, p. 3811 - 3814 (2017/07/26)
The regiocontrolled rearrangement of 1,2-diols has been achieved by controlling the loading of BF3·Et2O. Its applicability is showcased by the divergent synthesis of austrodoral, austrodoric acid, and 8-epi-11-nordriman-9-one, as well as a formal synthesis of siphonodictyal B and liphagal. A new light is shed on piancol-type rearrangements that will be useful in diversity-oriented synthesis of related natural products.
Mechanistically Driven Development of an Iron Catalyst for Selective Syn-Dihydroxylation of Alkenes with Aqueous Hydrogen Peroxide
Borrell, Margarida,Costas, Miquel
supporting information, p. 12821 - 12829 (2017/09/25)
Product release is the rate-determining step in the arene syn-dihydroxylation reaction taking place at Rieske oxygenase enzymes and is regarded as a difficult problem to be resolved in the design of iron catalysts for olefin syn-dihydroxylation with potential utility in organic synthesis. Toward this end, in this work a novel catalyst bearing a sterically encumbered tetradentate ligand based in the tpa (tpa = tris(2-methylpyridyl)amine) scaffold, [FeII(CF3SO3)2(5-tips3tpa)], 1 has been designed. The steric demand of the ligand was envisioned as a key element to support a high catalytic activity by isolating the metal center, preventing bimolecular decomposition paths and facilitating product release. In synergistic combination with a Lewis acid that helps sequestering the product, 1 provides good to excellent yields of diol products (up to 97% isolated yield), in short reaction times under mild experimental conditions using a slight excess (1.5 equiv) of aqueous hydrogen peroxide, from the oxidation of a broad range of olefins. Predictable site selective syn-dihydroxylation of diolefins is shown. The encumbered nature of the ligand also provides a unique tool that has been used in combination with isotopic analysis to define the nature of the active species and the mechanism of activation of H2O2. Furthermore, 1 is shown to be a competent synthetic tool for preparing O-labeled diols using water as oxygen source.
Visible light-promoted dihydroxylation of styrenes with water and dioxygen
Yang, Bo,Lu, Zhan
supporting information, p. 12634 - 12637 (2017/12/02)
An efficient visible light promoted metal-free dihydroxylation of styrenes with water and dioxygen has been developed for the construction of vicinal alcohols. The protocol was operationally simple with a broad substrate scope. The mechanistic studies demonstrated that one of the hydroxyl groups came from water and the other one came from molecular oxygen. Additionally, the β-alkyoxy alcohols could also be obtained using a similar strategy.
Iron-Catalyzed Enantioselective Epoxidations with Various Oxidants: Evidence for Different Active Species and Epoxidation Mechanisms
Zima, Alexandra M.,Lyakin, Oleg Y.,Ottenbacher, Roman V.,Bryliakov, Konstantin P.,Talsi, Evgenii P.
, p. 60 - 69 (2017/05/31)
Iron complexes with chiral bipyrrolidine-derived aminopyridine (PDP) ligands are among the most efficient Fe-based bioinspired catalysts for regio- and stereoselective oxidation of C-H and C=C moieties with hydrogen peroxide. Besides hydrogen peroxide, other oxidants (peroxycarboxylic acids and organic hydroperoxides) can be effectively used. In this work, we have examined the mechanistic landscape of the Fe(PDP) catalyst family with various oxidants: H2O2, organic hydroperoxides, and peracids. The combined EPR spectroscopic, enantioselectivity, Hammett, Z-stilbene epoxidation stereoselectivity, and 18O-labeling data witness that the same oxoiron complexes [(L)FeV=O(OC(O)R)]2+ are the actual epoxidizing species in both the catalyst systems (L)Fe/H2O2/carboxylic acid and (L)Fe/AlkylOOH/carboxylic acid. On the contrary, in the systems (L)Fe/R2C(O)OOH (R2 = CH3 or 3-Cl-C6H4), in the presence or in the absence of carboxylic acid, the epoxidation is predominantly conducted by the acylperoxo-iron(III) intermediates [(L)FeIII(OOC(O)R2)]2+, in a concerted fashion.
