- Selective benzylic C–H monooxygenation mediated by iodine oxides
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A method for the selective monooxdiation of secondary benzylic C–H bonds is described using an N-oxyl catalyst and a hypervalent iodine species as a terminal oxidant. Combinations of ammonium iodate and catalytic N-hydroxyphthalimide (NHPI) were shown to be effective in the selective oxidation of n-butylbenzene directly to 1-phenylbutyl acetate in high yield (86%). This method shows moderate substrate tolerance in the oxygenation of substrates containing secondary benzylic C–H bonds, yielding the corresponding benzylic acetates in good to moderate yield. Tertiary benzylic C–H bonds were shown to be unreactive under similar conditions, despite the weaker C–H bond. A preliminary mechanistic analysis suggests that this NHPI-iodate system is functioning by a radical-based mechanism where iodine generated in situ captures formed benzylic radicals. The benzylic iodide intermediate then solvolyzes to yield the product ester.
- LaMartina, Kelsey B.,Kuck, Haley K.,Oglesbee, Linda S.,Al-Odaini, Asma,Boaz, Nicholas C.
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supporting information
p. 602 - 609
(2019/04/17)
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- Studies on the chemoenzymatic synthesis of (R)- and (S)-methyl 3-aryl-3-hydroxypropionates: The influence of toluene-pretreatment of lipase preparations on enantioselective transesterifications
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Two series (para- and meta-substituted) of racemic methyl esters of 3-aryl-3-hydroxypropionic acid were prepared after which the enantiomers were separated by an enzyme-catalyzed transesterification. Several lipases were investigated as the catalyst. The influence of the enzyme pretreatment, as well as substrate concentration, reaction temperature, stirring manner, and substrate conversion on the stereochemical outcome of the biotransformation process were investigated in detail. The best results were achieved by using solvent-pretreated lipase from Pseudomonas fluorescens or Burkholderia cepacia suspended in toluene, and vinyl acetate as the acetyl group donor.
- Borowiecki, Pawel,Bretner, Maria
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p. 925 - 936
(2013/09/23)
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- Palladium-Catalyzed Three-Component coupling reactions: 1,1 -Difunctionalization of activated alkenes
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A three-component coupling reaction was developed to access 3,3-oxyarylpropionate derivatives. Each of the three reaction components can be varied, allowing the modular synthesis of a range of important chiral building blocks. Wiley-VCH Verlag GmbH & Co, KGaA.
- Rodriguez, Arantxa,Moran, Wesley J.
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supporting information; experimental part
p. 1313 - 1316
(2009/07/26)
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- Process for separating zinc salts from zinc alcoholates or zinc amides containing non-aqueous synthesis solvents
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A process for the removal of zinc from organic solutions containing zinc alcoholates or zinc amides comprises addition of an alkylating, arylating, acylating or silylating agent in the presence of a precipitating agent having at least two nitrogen donors followed by separation of the precipitated solid.
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Page/Page column 11
(2010/02/06)
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- Dehydroacetoxylation and Acetate Transesterification in the Reactions of erythro- and threo-Methyl 3-(Substituted acetoxy)-2-halogeno-3-phenylpropanoates with Triethylamine
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The response of the rate of triethylamine-induced dehydroacetoxylation of methyl threo-3-acetoxy-2-halogeno-3-phenylpropanoate to the influence of substituents in the leaving group points to a change in mechanism from (E1cB)I to a concerted process of the carbanion type.On the other hand, the erythro-isomers seem to undergo elimination exclusively through a carbanionic pathway.The effect of the acetoxy substituents upon the competitive transesterification is discussed.
- Garay, Raul O.,Cabaleiro, Mercedes C.
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p. 1643 - 1648
(2007/10/02)
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- TRANSFORMATIONS OF ARYL-SUBSTITUTED MONO- AND DIMETHOXYCYCLOPROPANES BY THE ACTION OF NITRATING AGENTS
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It was shown that the three-membered ring in 1,1-dimethoxy-2-phenylcyclopropane undergoes oxidative cleavage under the influence of both nitric acid and nitronium fluoroborate in acetic anhydride, leading to the formation of methyl cinnamate and 2-phenyl-2-acetoxypropionate.The ratio of the obtained esters depends on the reaction temperature and does not result from their mutual transformations.Under the same conditions 1-methoxy-2-(2-nitrophenyl)cyclopropane is converted mainly into o-nitrocinnamaldehyde and 5-methoxy-3-(2-nitrophenyl)-Δ2-isoxazoline.The formation of this substituted isoxazoline becomes predominant when the reaction is carried out with nitronium fluoroborate in nitromethane.
- Novokreshchennykh, V. D.,Mochalov, S. S.,Lukashova, E. A.,Shabarov, Yu. S.
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