1117-86-8Relevant articles and documents
Epoxidation of alkenes catalyzed by some molybdenum(0) and molybdenum(IV) complexes
Acharya, Sitaram,Hanna, Tracy A.
, p. 113 - 123 (2016)
Catalytic epoxidations of styrene, cyclohexene, 1-octene, and 3,3-dimethyl-1-butene have been explored utilizing a variety of molybdenum(0) and molybdenum(IV) complexes as precatalysts and tert-butylhydroperoxide (TBHP) as oxidant. The catalytic activities of the complexes MoCl4(CH3CN)2, Mo(CO)3(PTA)3 (PTA = 1,3,5-triaza-7-phosphaadamantane), Mo(CO)3(Mes), and a molybdenum(IV) calix[4]arene salt, [Et3NH][Mo{tBuC4}Cl(CH3CN)] have been investigated. The progress of reactions was monitored with reference to an internal standard by means of 1H NMR spectroscopy. Most of the complexes were found to be effective precatalysts with low catalyst loadings, giving rise to good to excellent conversion of alkenes and yield of the epoxides with the formation of minimal amount of corresponding diol and other side products. The catalytic reactions were found to be most efficient between 100 and 110 °C in minimal solvent or without added solvent.
Nonheme manganese-catalyzed asymmetric oxidation. A lewis acid activation versus oxygen rebound mechanism: Evidence for the "third oxidant"
Ottenbacher, Roman V.,Bryliakov, Konstantin P.,Talsi, Evgenii P.
, p. 8620 - 8628 (2010)
The catalytic properties of a series of chiral nonheme aminopyridinylmanganese(II) complexes [LMnII(OTf)2] were investigated. The above complexes were found to efficiently catalyze enantioselective olefin oxidation to the corresponding epoxides with different oxidants (peroxycarboxylic acids, alkyl hydroperoxides, iodosylarenes, etc.) with high conversions and selectivities (up to 100%) and enantiomeric excesses (up to 79%). The effect of the ligand structure on the catalytic performance was probed. Epoxidation enantioselectivities were found to be strongly dependent on the structure of the oxidants (performic, peracetic, and m-chloroperbenzoic acids; tert-butyl and cumyl hydroperoxides; iodosylbenzene and iodosylmesitylene), thus bearing evidence that the terminal oxidant molecule is incorporated in the structure of the oxygen-transferring intermediates. High-valence electron-paramagnetic-resonance-active manganese complexes [LMnIV=O]2+ and [LMnIV(μ-O) 2MnIIIL]3+ were detected upon interaction of the starting catalyst with the oxidants. The high-valence complexes did not epoxidize styrene and could themselves only contribute to minor olefin oxidation sideways. However, the oxomanganese(IV) species were found to perform the Lewis acid activation of the acyl and alkyl hydroperoxides or iodosylarenes to form the new type of oxidant [oxomanganese(IV) complex with a terminal oxidant], with the latter accounting for the predominant enantioselective epoxidation pathway in the nonheme manganese-catalyzed olefin epoxidations.
Rate-determining water-assisted O-O bond cleavage of an Fe III-OOH intermediate in a bio-inspired nonheme iron-catalyzed oxidation
Oloo, Williamson N.,Fielding, Andrew J.,Que, Lawrence
, p. 6438 - 6441 (2013)
Hydrocarbon oxidations by bio-inspired nonheme iron catalysts and H 2O2 have been proposed to involve an FeIII-OOH intermediate that decays via a water-assisted mechanism to form an Fe V(O)(OH) oxidant. Herein we report kinetic evidence for this pathway in the oxidation of 1-octene catalyzed by [FeII(TPA)(NCCH 3)]2+ (1, TPA = tris(2-pyridylmethyl)amine). The (TPA)FeIII(OOH) intermediate 2 can be observed at -40 C and is found to undergo first-order decay, which is accelerated by water. Interestingly, the decay rate of 2 is comparable to that of product formation, indicating that the decay of 2 results in olefin oxidation. Furthermore, the Eyring activation parameters for the decay of 2 and product formation are identical, and both processes are associated with an H2O/D2O KIE of 2.5. Taken together with previous 18O-labeling data, these results point to a water-assisted heterolytic O-O bond cleavage of 2 as the rate-limiting step in olefin oxidation.
Iron-catalyzed olefin cis-dihydroxylation by H2O2: Electrophilic versus nucleophilic mechanisms
Fujita, Megumi,Costas, Miquel,Que Jr., Lawrence
, p. 9912 - 9913 (2003)
Previous studies have classified a series of nonheme iron catalysts for olefin cis-dihydroxylation by H2O2 into two groups. Complex 1, [(TPA)Fe(OTf)2], representative of Class A catalysts, forms a low-spin FeIII-OOH intermediate that gives rise to a high-valent FeV(=O)OH oxidant. The preference of this catalyst for electron-rich olefins demonstrates its electrophilic character. On the other hand, complex 2, [(6-Me3-TPA)Fe(OTf)2], representative of Class B catalysts, prefers instead to oxidize electron-deficient olefins, suggesting an oxidant with nucleophilic character. It is suggested that such a nucleophilic oxidant may be the high-spin FeIII-OOH intermediate derived from 2 or the FeIV(=O)(?OH) species derived therefrom. Copyright
OsO(4) in ionic liquid [Bmim]PF(6): a recyclable and reusable catalyst system for olefin dihydroxylation. remarkable effect of DMAP.
Yao, Qingwei
, p. 2197 - 2199 (2002)
[reaction: see text] The combination of the ionic liquid [bmim]PF(6) and DMAP provides a most simple and practical approach to the immobilization of OsO(4) as catalyst for olefin dihydroxylation. Both the catalyst and the ionic liquid can be repeatedly recycled and reused in the dihydroxylation of a variety of olefins with only a very slight drop in catalyst activity.
Ligand topology effects on olefin oxidations by bio-inspired [Fe II(N2Py2)] catalysts
Mas-Balleste, Ruben,Costas, Miquel,Van Den Berg, Tieme,Que Jr., Lawrence
, p. 7489 - 7500 (2006)
Linear tetradentate N2Py2 ligands can coordinate to an octahedral FeII center in three possible topologies (cis-α, cis-β, and trans). While for the N,N'-bis(2-pyridylmethyl)-l,2- diaminoethane (bpmen) complex, only the cis-α topology has been observed, for N,N'-bis(2-pyridylmethyl)-1,2-diamino-cyclohexane (bpmcn) both cis-α and cis-β isomers have been reported. To date, no facile interconversion between cis-α and cis-β topologies has been observed for iron(II) complexes even at high temperatures. However, this work provides evidence for facile interconversion in solution of cis-α, cis-β, and trans topologies for [Fe(bpmpn)X2] (bpmpn = N, N'-bis(2-pyridylmethyl)-1,3- diaminopropane; X = triflate, CH3CN) complexes. As reported previously, the catalytic behavior of cis-α and cis-β isomers of [Fe(bpmcn)(OTf)2] with respect to olefin oxidation depends dramatically on the geometry adopted by the iron complex. To establish a general pattern of the catalysis/ topology dependence, this work presents an extended comparison of the catalytic behavior for oxidation of olefins of a family of [Fe(N2py2)] complexes that present different topologies. 18O labeling experiments provide evidence for a complex mechanistic land-scape in which several pathways should be considered. Complexes with a trans topology catalyze only non-water-assisted epoxidation. In contrast, complexes with a cis-α topology, such as [Fe(bpmen)X2] and [Fe(α-bpmcn)-(OTf)2], can catalyze both epoxidation and cis-dihydroxylation through a water-assisted mechanism. Surprisingly, [Fe(bpmpn)X2] and [Fe(β-bpmcn)-(OTf)2] catalyze epoxidation via a water-assisted pathway and cis-dihydroxylation via a non-water-assisted mechanism, a result that requires two independent and distinct oxidants.
Access to enantiopure aromatic epoxides and diols using epoxide hydrolases derived from total biofilter DNA
Kotik, Michael,Stepanek, Vaclav,Grulich, Michal,Kyslik, Pavel,Archelas, Alain
, p. 41 - 48 (2010)
Metagenomic DNA is a rich source of genes encoding novel epoxide hydrolases (EHs). We retrieved two genes encoding functional EHs from total DNA isolated from biofilter-derived biomass, using PCR with EH-specific degenerate primers followed by genome-walking PCR. The degenerate primers were based on two EH-specific consensus sequences: HGWP and GHDWG. The resulting recombinant EHs, Kau2 and Kau8, were expressed in Escherichia coli, and their enantioselectivity and regioselectivity were determined using 13 different epoxide substrates. The EH Kau2 had broad substrate specificity and preferentially hydrolyzed epoxides with S-configuration. It showed high enantioselectivity towards aromatic epoxides such as styrene oxide, p-nitrostyrene oxide, and trans-1-phenyl-1,2-epoxypropane. In addition, Kau2 showed enantioconvergent hydrolysis activity. The EH Kau8 also showed broad substrate specificity and preferentially hydrolyzed epoxides with R-configuration. High enantioselectivity was observed for p-nitrostyrene oxide, and the hydrolysis activity of Kau8 was less enantioconvergent than that of Kau2. To determine the usefulness of Kau2 for synthetic applications, preparative-scale biohydrolysis reactions were performed. Specifically, two kinetic resolutions were carried out with 80 g/L of racemic trans-1-phenyl-1,2-epoxypropane, affording both (1R,2R)-epoxide and the corresponding (1R,2S)-diol in high enantiomeric excess (>99%) and good yield (>45%). In addition, a process based on enantioconvergent hydrolysis by the EH Kau2 was established for racemic cis-1-phenyl-1,2-epoxypropane at a concentration of 13 g/L, resulting in the formation of the corresponding (1R,2R)-diol with a 97% yield and an enantiomeric excess exceeding 98%.
Total synthesis of the salicyldehydroproline-containing antibiotic promysalin
Kaduskar, Rahul D.,Dhavan, Atul A.,Dallavalle, Sabrina,Scaglioni, Leonardo,Musso, Loana
, p. 2034 - 2041 (2016)
A convergent total synthesis of promysalin, a metabolite of Pseudomonas putida RW10S1 with antibiotic activity, is described. The synthetic approach is based around a salicyldehydroproline core and a dihydroxymyristamide fragment. Crucial steps include a MacMillan asymmetric α-hydroxylation applied for the construction of the myristamide framework, and a lactam reduction by Superhydride to obtain the dehydroproline fragment. Because of the modular nature of the synthesis, ready access to analogues for biological evaluation is available.
Iron-catalyzed olefin cis-dihydroxylation using a bio-inspired N,N, O-ligand
Oldenburg, Paul D.,Shteinman, Albert A.,Que Jr., Lawrence
, p. 15672 - 15673 (2005)
Nature has evolved enzymes that carry out the cis-dihydroxylation of C=C bonds in the biodegradation of arenes in the environment. These enzymes, called Rieske dioxygenases, have mononuclear iron centers coordinated to a 2-His-1-carboxylate facial triad motif that has emerged as a common structural element among many nonheme iron enzymes. In contrast, olefin cis-dihydroxylation is conveniently carried out by OsO4 and related species in synthetic procedures. To develop more environmentally benign strategies for carrying out these transformations, we have designed Ph-DPAH [(di-(2-pyridyl)methyl)benzamide], a tridentate ligand that mimics the facial N,N,O site of the mononuclear iron center in the Rieske dioxygenases. Its iron(II) complex has been found to catalyze olefin cis-dihydroxylation almost exclusively and with high H2O2 conversion efficiency on a wide range of substrates. and 18O labeling experiments suggest the participation of an FeV oxidant. Copyright
Dendrimer crown-ether tethered multi-wall carbon nanotubes support methyltrioxorhenium in the selective oxidation of olefins to epoxides
Bizzarri, Bruno Mattia,Botta, Lorenzo,Crucianelli, Marcello,Fanelli, Angelica,Ferella, Francesco,Gontrani, Lorenzo,Sadun, Claudia,Saladino, Raffaele
, p. 17185 - 17194 (2020)
Benzo-15-crown-5 ether supported on multi-wall carbon nanotubes (MWCNTs) by tethered poly(amidoamine) (PAMAM) dendrimers efficiently coordinated methyltrioxorhenium in the selective oxidation of olefins to epoxides. Environmentally friendly hydrogen peroxide was used as a primary oxidant. Up to first and second generation dendrimer aggregates were prepared by applying a divergent PAMAM methodology. FT-IR, XRD and ICP-MS analyses confirmed the effective coordination of methyltrioxorhenium by the benzo-15-crown-5 ether moiety after immobilization on MWCNTs. The novel catalysts converted olefins to the corresponding epoxides in high yield without the use of Lewis base additives, or anhydrous hydrogen peroxide, the catalyst being stable for more than six oxidative runs. In the absence of the PAMAM structure, the synthesis of diols largely prevailed.
