- Visible-light-induced thiotrifluoromethylation of terminal alkenes with sodium triflinate and benzenesulfonothioates
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An unconventional reductive quenching cycle was developed to realize the visible-light-induced thiotrifluoromethylation of terminal alkenes. CF3SO2Na was used as an easy to handle CF3 radical source to afford the desired products in moderate to good yields. Mild reaction conditions and a broad substrate scope feature in this transformation.
- Kong, Weiguang,An, Hejun,Song, Qiuling
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supporting information
p. 8968 - 8971
(2017/08/15)
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- Bioproduction of chiral epoxyalkanes using styrene monooxygenase from rhodococcus sp. ST-10 (RhSMO)
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We describe the enantioselective epoxidation of straight-chain aliphatic alkenes using a biocatalytic system containing styrene monooxygenase from Rhodococcus sp. ST-10 and alcohol dehydrogenase from Leifsonia sp. S749. The biocatalyzed enantiomeric epoxidation of 1-hexene to (S)-1,2-epoxyhexane (44.6 mM) using 2-propanol as the hydrogen donor was achieved under optimized conditions. The biocatalyst had broad substrate specificity for various aliphatic alkenes, including terminal, internal, unfunctionalized, and di- and tri-substituted alkenes. Here, we demonstrate that this biocatalytic system is suitable for the efficient production of enantioenriched (S)-epoxyalkanes.
- Toda, Hiroshi,Imae, Ryouta,Itoh, Nobuya
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p. 3443 - 3450
(2015/02/05)
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- Cyclohexanones by Rh-mediated intramolecular C-H insertion
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Some long chain α-aryl α-diazo ketones under Rh catalysis cyclize efficiently to the corresponding cyclohexanones. This is in marked contrast to the cyclizations of α-diazo β-ketoesters, which consistently deliver cyclopentanone products.
- Taber, Douglass F.,Paquette, Craig M.,Gu, Peiming,Tian, Weiwei
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p. 9772 - 9780
(2013/10/22)
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- Low catalyst loading in ring-closing metathesis reactions
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An efficient procedure is described for ring-closing metathesis reactions. A conversion of 95 % for diethyl diallylmalonate in dilute solution could be achieved within a few minutes, reaching TOF=4173min-1, with very low loading of commercially available Ru catalysts that contained unsaturated NHC ligands. In general, only 50 to 250ppm of the catalyst is required to achieve near-quantitative conversion into a broad variety of 5-16-membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5-8-membered N-tert-butoxycarbonyl (N-Boc)- and N-para-toluenesulfonyl (N-Ts)-protected cyclic amines and 9-16-membered lactones. The synthesis of macrocyclic proline-based lactams required slightly higher catalyst loadings. Along with monocyclic products, oligomeric byproducts, mostly cyclodimers, were isolated and characterized. Getting some closure: An efficient procedure is described for ring-closing metathesis reactions in which only 50 to 250ppm of catalyst is required to effect almost-quantitative conversion into a broad range of 5-16-membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5-8-membered N-protected cyclic amines, 9-16-membered lactones, and 11-16-membered proline-based lactams. Copyright
- Kadyrov, Renat
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supporting information
p. 1002 - 1012
(2013/02/23)
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- Enantioselective synthesis of a fluorinated analogue of the orsellinic acid-type twelve-membered lactone lasiodiplodin
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The chemoenzymatic synthesis of the racemate and the one enantiomer of the fluorinated analogue 8 of the natural cyclooxygenase inhibitor lasiodiplodin is decribed. A lipase-mediated deracemization of the fluorohydrin 18 provided the chiral, nonracemic building block for the enantioselective synthesis of the title compound. The key step was the formation of the 12-membered lactene by a ring-closing metathesis.
- Runge,Haufe
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p. 8737 - 8742
(2007/10/03)
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- Stereospecific rhenium catalyzed desulfurization of thiiranes
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Methyltrioxorhenium catalyzes the efficient and stereospecific desulfurization of thiiranes by triphenylphosphine at room temperature, moreso when MTO has been pretreated with hydrogen sulfide, with a Re(v) species as the active form of the catalyst.
- Jacob, Josemon,Espenson, James H.
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p. 1003 - 1004
(2007/10/03)
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- C2-bridged metallocene dichloride complexes of the types (C13H8-CH2CHR-C9H 6-nR′n)ZrCl2 and (C13H8-CH2CHR-C13H 8)MCl2 (n=0, 1; R=H, alkenyl; R′=alkenyl, benzyl; M=Zr, Hf) as self-immobilizing catalyst precursors for ethylene polymerization
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A total of 15 C2-bridged fluorenylidene indenylidene and bis(fluorenylidene) metal dichloride complexes (metal=Zr, Hf) and the corresponding ligand precursors have been prepared and characterized. ω-Alkenyl substituents with various chain lengths in the C2-bridge or in position 3 of the indenylidene moiety have an impact on the polymerization activity of the catalysts and the molecular weights of the produced polyethylenes. These ω-alkenyl substituents cause 'self-immobilization' due to their incorporation into the backbone of a growing polymer chain providing heterogeneous catalyst systems.
- Alt, Helmut G.,Jung, Michael
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- Environmentally friendly catalysis using supported reagents: Catalytic epoxidation using a chemically modified silica gel1
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A new heterogeneous catalyst based on a chemically modified mesoporous silica gel possessing immobilised cobalt ions is developed and successfully applied to the epoxidation of alkenes.
- Butterworth, Andrew J.,Clark, James H.,Walton, Paul H.,Barlow, Simon J.
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p. 1859 - 1860
(2007/10/03)
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- Cobalt(II) catalysed reaction of alkenes with aliphatic aldehydes and molecular oxygen: Scope and mechanism
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A variety of cobalt(II) complexes can be prepared using Schiff's bases derived from aromatic aldehydes and amines or α-aminoesters. These complexes are versatile catalyst for the reaction between aliphatic aldehydes and various alkenes. The outcome of the reaction is controlled by the electronic nature of the alkene as the electron deficient alkenes undergo oxidative addition of aldehydes followed by dioxygen incorporation to yield 2-hydroxy(acyloxy)-4-oxoesters or nitriles whereas unactivated or electron rich alkenes afford the corresponding epoxides. These reactions are proceeding via a radical pathway and a common acylcobalt intermediate is proposed for the formation of 4 as well as the epoxides 7.
- Bhatia, Sonika,Punniyamurthy,Bhatia, Beena,Iqbal, Javed
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p. 6101 - 6122
(2007/10/02)
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- Synthesis of Cyclic Ethers via Bromine Assisted Epoxide Ring Expansion
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Neighbouring group participation by epoxide oxygen in the opening of bromonium ions results in the stereoselective synthesis of cyclic ethers. 9-Oxabicyclonon-4-ene gives trans, trans-2,6-dibromo-9-oxabicyclononane and trans,trans-2,5-dibromo-9-oxabicyclononane.Sequential bromination and Bu3SnH reduction converts 1,2-epoxyhex-5-ene into cis- and trans-2,5-dimethyltetrahydrofuran and 2-methyltetrahydropyran while (+)-cis-limonene oxide is converted into non-chiral cineole.
- Davies, Stephen G.,Polywka, Mario E. C.,Thomas, Susan E.
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p. 1277 - 1282
(2007/10/02)
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- Mechanistic Studies on Non-Heme Iron Monooxygenase Catalysis: Epoxidation, Aldehyde Formation, and Demethylation by the ω-Hydroxylation System of Pseudomonas oleovorans
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In previous work we have established that the "ω-hydroxylation" system of P. oleovorans readily converts terminal olefins to the corresponding 1,2-oxides and does so stereoselectively.We also demonstrated loss of olefin configuration during enzymatic epoxidation, a result inconsistent with a concerted epoxidation mechanism (J.Am.Chem.Soc. 1977, 99, 2017-2024).Since loss of olefin configuration is unprecedented for monooxygenase-catalyzed epoxidations these studies have been confirmed with isolated enzymes and further extended in order to probe the mechanism of non-heme iron monooxygenase catalysis.Enzymatic epoxidation of both cis- and trans-1-deuterio-1-octene proceeds with about 70percent inversion of the olefinic configuration, with corresponding results being obtained for the two olefins.As we reported in a preliminary communication (Bio/Technology 1983, 1, 677-686, the ω-hydroxylation system also produces aldehydes from olefins.Aldehyde formations exhibits the reaction characteristics expected for the usual oxygenase pathway.Deuterium migration from C-1 to C-2 occurs in formation of aldehyde from olefin, although loss of deuterium also occurs.The ω-hydroxylation system was found to efficiently catalyze O-demethylation of heptyl methyl ether, the first demonstration of such activity for a non-heme iron monooxygenase of this type.Taken together, the results provide support for a two-step mechanism involving enzyme generated species with cationic and/or radical character, which accounts for the stereoselectivity, configurational loss, substrate specificity, formation of aldehydes with deuterium migration, and demethylation activity exhibited by this enzyme system.
- Katopodis, Andreas, G.,Wimalasena, Kandatege,Lee, Joseph,May, Sheldon W.
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p. 7928 - 7935
(2007/10/02)
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- Palladium-catalysed Synthesis of endo- and exo-Brevicomin and Related Di- and Tri-oxabicyclo Systems.
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Ethyl nona-3,8-dienoate prepared from the palladium-catalysed reaction of butadiene with carbon monoxide and ethanol was found to consist of a 79:21 mixture of trans- and cis-isomers.The ester was used to prepare threo- and erythro-3,4-dihydroxynon-8-ene which were cylised by a Wacker-type catalyst (PdCl2 - CuCl2 - O2) to exo- and endo-brevicomin.Analogous cyclisations were effected on several other ene-diols derived from octa-1,6-diene, octa-1,7-diene, allyl glycidyl ether and two substituted diallyl ethers.The mechanism of the key cyclisation step is discussed.
- Byrom, Norman T.,Grigg, Ronald,Kongkathip, Boonsong,Reimer, Gerald,Wade, Alan R.
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p. 1643 - 1653
(2007/10/02)
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