81691-59-0Relevant academic research and scientific papers
Preparation, characterization and catalytic properties of polyaniline-supported metal complexes
Choudary, Boyapati M.,Roy, Moumita,Roy, Sarabindu,Kantam, M. Lakshmi,Sreedhar, Bojja,Kumar, Karasala Vijay
, p. 1734 - 1742 (2006)
Polyaniline-supported Sc, In, Pd, Os and Re catalysts were prepared by using a simple protocol and the thus prepared catalysts were well characterized using FTIR, XPS, UV-Vis/DRS, TGA-DTA. All the catalysts were successfully employed in a wide range of organic transformations such as cyanation and allylation of carbonyl compound, Suzuki coupling of aryl halides and boronic acids, and, most importantly, in asymmetric dihydroxylation of olefins to afford optically active vicinal diols. All the catalysts were separated from the reaction mixture by simple filtration and reused with consistent activity for five cycles without noticeable leaching of metal from the support.
Racemic or enantioselective osmium-catalyzed dihydroxylation of olefins under near-neutral conditions
Blumberg, Shawn,Martin, Stephen F.
, p. 7 - 14 (2020/10/08)
K3Fe(CN)6 and NaIO4 serve as catalytic co-oxidants for osmium-catalyzed dihydroxylations that are performed under near-neutral conditions with K2S2O8 as the stoichiometric oxidant and Na2HPO4 as the base. By using either quinuclidine or hydroquinidine 1,4-phthalazinediyl ether [(DHQD)2Phal], good yields of racemic or enantioenriched diols are obtained. This simple, biphasic procedure offers advantages over other neutral dihydroxylation protocols that use N-methylmorpholine oxide as the stoichiometric oxidant, by suppressing the secondary catalytic cycle that leads to reduced enantioselectivities. The utility of the procedure, which is nicely suited for base-labile starting materials or products, is demonstrated by performing the dihydroxylation in the presence of an aliphatic aldehyde moiety.
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.
A Well-Defined Osmium-Cupin Complex: Hyperstable Artificial Osmium Peroxygenase
Fujieda, Nobutaka,Nakano, Takumi,Taniguchi, Yuki,Ichihashi, Haruna,Sugimoto, Hideki,Morimoto, Yuma,Nishikawa, Yosuke,Kurisu, Genji,Itoh, Shinobu
supporting information, p. 5149 - 5155 (2017/05/04)
Thermally stable TM1459 cupin superfamily protein from Thermotoga maritima was repurposed as an osmium (Os) peroxygenase by metal-substitution strategy employing the metal-binding promiscuity. This novel artificial metalloenzyme bears a datively bound Os ion supported by the 4-histidine motif. The well-defined Os center is responsible for not only the catalytic activity but also the thermodynamic stability of the protein folding, leading to the robust biocatalyst (Tm ≈ 120 °C). The spectroscopic analysis and atomic resolution X-ray crystal structures of Os-bound TM1459 revealed two types of donor sets to Os center with octahedral coordination geometry. One includes trans-dioxide, OH, and mer-three histidine imidazoles (O3N3 donor set), whereas another one has four histidine imidazoles plus OH and water molecule in a cis position (O2N4 donor set). The Os-bound TM1459 having the latter donor set (O2N4 donor set) was evaluated as a peroxygenase, which was able to catalyze cis-dihydroxylation of several alkenes efficiently. With the low catalyst loading (0.01% mol), up to 9100 turnover number was achieved for the dihydroxylation of 2-methoxy-6-vinyl-naphthalene (50 mM) using an equivalent of H2O2 as oxidant at 70 °C for 12 h. When octene isomers were dihydroxylated in a preparative scale for 5 h (2% mol cat.), the terminal alkene octene isomers was converted to the corresponding diols in a higher yield as compared with the internal alkenes. The result indicates that the protein scaffold can control the regioselectivity by the steric hindrance. This protein scaffold enhances the efficiency of the reaction by suppressing disproportionation of H2O2 on Os reaction center. Moreover, upon a simple site-directed mutagenesis, the catalytic activity was enhanced by about 3-fold, indicating that Os-TM1459 is evolvable nascent osmium peroxygenase.
Cis-Dihydroxylation of electron deficient olefins catalysed by an oxo-bridged diiron(III) complex with H2O2
Kejriwal, Ambica,Biswas, Sachidulal,Biswas, Achintesh N.,Bandyopadhyay, Pinaki
, p. 77 - 84 (2016/01/09)
Room temperature oxidation of olefins catalysed by a symmetrical (μ-oxo)(μ-hydroxo)diiron(III) complex (1) based on the amino pyridyl ligand bpmen (bpmen = N,N′-dimethyl-N,N′-bis(2-pyridyl methyl)ethane-1,2-diamine) with hydrogen peroxide under the conditions of limiting substrate is described. Excellent substrate conversions have been achieved under ambient reaction conditions. The olefin oxidation efficacy of the 1/H2O2 system has been found to get improved in presence of acetic acid. The catalytic system has been shown to oxidise electron-deficient olefins to the corresponding cis-diols, while epoxidation is favoured in case of electron-rich olefins. The μ-oxo diiron(III) core of the catalyst 1 has been found be regenerated after the catalytic turnovers. Addition of a second batch of substrate and oxidant at the end of the olefin oxidation results in the formation of almost identical amounts of epoxides/diols. Moreover, the regenerated catalyst exhibits a significantly higher preference towards the oxidation of electron-deficient olefins.
Enantioselective bio-hydrolysis of various racemic and meso aromatic epoxides using the recombinant epoxide hydrolase Kau2
Zhao, Wei,Kotik, Michael,Iacazio, Gilles,Archelas, Alain
, p. 1895 - 1908 (2015/06/02)
Abstract Epoxide hydrolase Kau2 overexpressed in Escherichia coli RE3 has been tested with ten different racemic and meso α,β-disubstituted aromatic epoxides. Some of the tested substrates were bi-functional, and most of them are very useful building blocks in synthetic chemistry applications. As a general trend Kau2 proved to be an extremely enantioselective biocatalyst, the diol products and remaining epoxides of the bioconversions being obtained - with two exceptions - in nearly enantiomerically pure form. Furthermore, the reaction times were usually very short (around 1 h, except when stilbene oxides were used), and the use of organic co-solvents was well tolerated, enabling very high substrate concentrations (up to 75 g/L) to be reached. Even extremely sterically demanding epoxides such as cis- and trans-stilbene oxides were transformed on a reasonable time scale. All reactions were successfully conducted on a 1 g preparative scale, generating diol- and epoxide-based chiral synthons with very high enantiomeric excesses and isolated yields close to the theoretical maximum. Thus we have here demonstrated the usefulness and versatility of lyophilized Escherichia coli cells expressing Kau2 epoxide hydrolase as a highly enantioselective biocatalyst for accessing very valuable optically pure aromatic epoxides and diols through kinetic resolution of racemates or desymmetrization of meso epoxides.
Metal-free ring-opening of epoxides with potassium trifluoroborates
Roscales, Silvia,Csaky, Aurelio G.
supporting information, p. 454 - 456 (2014/01/06)
The ring-opening of epoxides with potassium trifluoroborates proceeds smoothly in the presence of trifluoroacetic anhydride under metal-free conditions. The reactions are regioselective and afford a single diastereomer. Both electron-rich and electron-poor aryltrifluoroborates are tolerated.
Osmium impregnated on magnetite as a heterogeneous catalyst for the syn-dihydroxylation of alkenes
Cano, Rafael,Pérez, Juana M.,Ramón, Diego J.
, p. 177 - 182 (2014/01/06)
A new catalyst derived from osmium has been prepared, fully characterized and tested in the dihydroxylation of alkenes. The catalyst was prepared by wet impregnation methodology of OsCl3·3H2O on a commercial micro-magnetite surface. The catalyst allowed the reaction with one of the lowest osmium loadings for a heterogeneous catalyst and was selective for the monodihydroxylation of 1,5-dienes. Moreover, the catalyst was easily removed from the reaction medium by the simple use of a magnet. The selectivity of catalyst is very high with conversions up to 99%. Preliminary kinetics studies showed a first-order reaction rate with respect to the catalyst.
Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: A simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide
Sugimoto, Hideki,Ashikari, Kenji,Itoh, Shinobu
, p. 2154 - 2160 (2013/09/23)
A simple protocol that uses [OsIII(OH)(H2O)(L-N 4Me2)](PF6)2 (1; L-N 4Me2=N,N′-dimethyl-2,11-diaza[3.3](2,6) pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os V(O)(OH) species (2), which is formed via the hydroperoxide adduct, an OsIII(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized. The wizard of Os: A simple protocol that uses [OsIII(OH)(H2O)(L-N4Me 2)](PF6)2 (1) and H2O2 for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups were converted into the corresponding vicinal diols in good to excellent yields. It has been confirmed that the OsV(O)(OH) species (2) is the active oxidant, which is formed via the hydroperoxide adduct A. Copyright
Asymmetric synthesis of 2,4,5-trisubstituted Δ2- thiazolines
Bengtsson, Christoffer,Nelander, Hanna,Almqvist, Fredrik
, p. 9916 - 9922 (2013/08/23)
Δ2-Thiazolines are interesting heterocycles that display a wide variety of biological characteristics. They are also common in chiral ligands used for asymmetric syntheses and as synthetic intermediates. Herein, we present asymmetric routes to
