- Iron catalyzed halogenation of benzylic aldehydes and ketones
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A simple and efficient iron-catalyzed method for chlorination of aromatic carbonyl compounds is reported. By using 4-10 mol% Fe(iii) oxo acetate catalyst, prepared by solid state atmospheric oxidation of Fe(ii) acetate, in combination with triethylsilane and chlorotrimethylsilane, hydrosilylation of benzylic carbonyl compounds with subsequent chlorination is achieved within a few hours at room temperature. This new method is mild and rapid compared to the conventional two step approach involving reduction and chlorination reactions in separate stages. Development of synthetic methodology is also supplemented here by kinetic investigation of the reaction mechanism, which supports the tentative mechanisms suggested previously for similar reactions. This journal is
- Savela, Risto,W?rn?, Johan,Murzin, Dmitry Yu.,Leino, Reko
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p. 2406 - 2417
(2015/04/14)
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- Supercritical carbon dioxide: A promoter of carbon-halogen bond heterolysis
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Amazing reaction medium: Supercritical carbon dioxide, with zero dipole moment, lower dielectric constant than pentane, and non-hydrogen-bonding behavior, ionizes carbon-halogen bonds, dissociates the resulting ion pairs, and escapes from capture by the carbocation intermediates at temperatures above 40 °C. These properties allow the observation of carbocation chemistry in the absence of acids.
- Delgado-Abad, Thais,Martinez-Ferrer, Jaime,Caballero, Ana,Olmos, Andrea,Mello, Rossella,Gonzalez-Nunez, Maria Elena,Perez, Pedro J.,Asensio, Gregorio
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p. 13298 - 13301
(2014/01/06)
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- Side Chain Hydroxylation of Aromatic Hydrocarbons by Fungi. Part 2. Isotope Effects and Mechanism
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The benzylic hydroxylation of ethylbenzene, p-diethylbenzene, tetralin, indane, and toluene by the fungi Mortierella isabellina, Cunninghamella echinulata, and Helminthosporium species has been investigated by the use of deuterium-labelled substrates.An i
- Holland, Herbert L.,Brown, Frances M.,Munoz, Benito,Ninnis, Ronald W.
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p. 1557 - 1564
(2007/10/02)
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- Stereochemical Dynamics of Aliphatic Hydroxylation by Cytochrome P-450
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Previous studies on the stereochemistry of hydroxylation by cytochrome P-450 enzymes have been contradictory and confusing.Therefore, the hydroxylation of four isotopically substituted phenylethane substrates has been examined with a single isozyme of rabbit liver microsomal cytochrome P-450.In each case the corresponding 1-phenylethanol was essentially the only product.With ordinary phenylethane, the product was 48percent R-1-phenylethanol and 52percent the S isomer.With (R)-phenylethane-1-d, the product was 42percent R alcohol, while with (S)-phenylethane-1-d the product was 70percent R alcohol.When the substrate was phenylethane-1,1-d2, 50percent R alcohol was produced.The alcohols from the single-deuterium-substituted substrates were highly enriched in deuterium, indicating the operation of a large deuterium isotope effect on hydrogen removal.Most importantly, 23-40percent of the hydroxylation events resulted in alcohol with configuration opposite to that of the original hydrocarbon substrate.These "crossover" events require the intermediacy of a discrete tricoordinate carbon intermediate.These data unambiguously demonstrate that hydroxylation stereospecificity must be enforced by the surrounding protein tertiary structure and is not an inherent feature of the cytochrome P-450 reaction mechanism.
- White, Ronald E.,Miller, John P.,Favreau, Leonard V.,Bhattacharyya, Apares
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p. 6024 - 6031
(2007/10/02)
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- FUNGAL HYDROXYLATION OF ETHYL BENZENE AND DERIVATIVES
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The fungus Mortierella isabellina converts ethyl benzene and a number of para-substituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 and 40percent.Hydrogen removal from the substrate preceeds product formation and is stereochemically independent of it.
- Holland, Herbert L.,Carter, Ian M.,Chenchaiah, P. Chinna,Khan, Shaheer H.,Munoz, Benito,et al.
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p. 6409 - 6412
(2007/10/02)
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- The preparation and characterization of benzocyclobutenylidene-, naphtho[b]cyclobutenylidene-, and η2-benzocyclobutadiene-η5-cyclopentadienyldicarbonyliron hexafluorophosphate
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The preparation and characterization of the first isolable cationic mononuclear complexes bearing a η2-cyclobutadienoid ligand or a carbene ligand lacking heteroatom stabilization are described. The reaction between 1-bromo-benzocyclobutene and Na[η5-C5H5(CO)2Fe] (NaFp) afforded η1-1-benzocyclobutenyl-η5-cyclopentadienyldicarbonyliron (III). Treatment of III with trityl hexafluorophosphate gave benzocyclobutenylidene-η5-cyclopentadienyldicarbonyliron hexafluorophosphate (V). Naphtho [b] cyclobutenylidene-η5-cyclopentadienyldicarbonyliron hexafluorophosphate (VI) was formed in an analogous manner. Both V and VI gave 1,1-disubstituted cyclobutenes when treated with nucleophilic reagents. η2-Benzocyclobutadiene-η5-cyclopentadienyldicarbonyliron hexafluorophosphate, (XIX), which was prepared by the oxidation of bis-1,2-(η5-cyclopentadienyldicarbonyliron)benzocyclobutene by trityl hexafluorophosphate, afforded trans-1,2-disubstituted benzocyclobutenes when treated with nucleophilic reagents. The η2-benzocyclobutadiene ligand of XIX was displaced by I- and trapped as the Diels--Alder adduct by 1,3-diphenylisobenzofuran.
- Sanders, Andrea,Bauch, Thomas,Magatti, Charles V.,Lorenc, Carol,Giering, Warren P.
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p. 359 - 375
(2007/10/05)
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