- Enantioselective one-pot catalytic synthesis of 4,5-epoxy-3-alkanols and 1-Phenyl-2,3-epoxy-1-alkanols from α,β-unsaturated aldehydes
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Conformationally restricted perhydrobenzoxazines have been demonstrated to be good chiral ligands for one-pot asymmetric ethylation/epoxidation, and the unprecedented arylation/epoxidation of trisubstituted α,β-unsaturated aldehydes. The scope of the reaction has been studied and a wide set of substrates with allylic strain of different nature has been explored, obtaining good or total diastereoselectivities in all cases. The enantiocontrol was good or high for the ethylation/epoxidation reaction, whereas it remained at moderate or good levels for the arylation/epoxidation. The reaction is general for trisubstituted enals, and alkylic and aromatic substituents are tolerated at both the α- and β-position of the unsaturated aldehyde; however, disubstituted enals remain challenging substrates. When the one-pot and two-pot protocols were compared, no significant differences concerning the stereocontrol were found, so the advantages of the one-pot procedure are clear. Copyright
- Infante, Rebeca,Hernandez, Yulan,Nieto, Javier,Andres, Celia
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supporting information
p. 4863 - 4869
(2013/08/23)
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- Asymmetric epoxidation via phase-transfer catalysis: Direct conversion of allylic alcohols into α,β-epoxyketones
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Studies into the use of a chiral phase-transfer catalyst in conjunction with sodium hypochlorite to effect the enantio-selective formation of α,β-epoxyketones from allylic alcohols are described.
- Lygo, Barry,To, Daniel C. M.
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p. 2360 - 2361
(2007/10/03)
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- Applications of free and resin-bound novel (trifluoromethyl)dioxiranes
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Recyclable resin-bound and other trifluoromethyl aryl ketones are efficient catalysts for oxone mediated epoxidations.
- Boehlow, Todd R.,Buxton, P. Christopher,Grocock, Estella L.,Marples, Brian A.,Waddington, Victoria L.
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p. 1839 - 1842
(2007/10/03)
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- Chemo- and stereoselective reduction of α,β-epoxyketones with diisopropoxytitanium(III) tetrahydroborate
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Reduction of α,β-epoxyketones with diisopropoxytitanium(III) tetrahydroborate in dichloromethane under mild conditions (-78°→20°C) provides anti- (or erythro-) α,β-epoxy alcohols in high yields with high degree of chemo- and stereoselectivity.
- Ravikumar,Chandrasekaran, Srinivasan
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p. 9137 - 9142
(2007/10/03)
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- Oxiranyllithium reagents: Generation from organotin precursors, addition to aldehydes and ketones, and dimerization to α,α′-dialkoxyolefins
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Oxiranyllithium compounds can be generated from organotin precursors by tin-lithium exchange with butyllithium in THF at -90°C. In the presence of TMEDA, they react with aldehydes and ketones to give epoxy alcohols in good yields. In the absence of TMEDA, they dimerize to α,α′-dialkoxyolefins.
- Lohse, Peter,Loner, Helena,Acklin, Pierre,Sternfeld, Francine,Pfaltz, Andreas
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p. 615 - 618
(2007/10/02)
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- A Novel Probe for Free Radicals featuring Epoxide Cleavage
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This paper describes the identification of carbon-carbon bond cleavage within a defined range of epoxides as being a reaction type which is specifically diagnostic of free radicals adjacent to the epoxide.The speed of the epoxide cleavage is greater than
- Dickinson, Julia M.,Murphy, John A.,Patterson, Christopher W.,Wooster, Nicholas F.
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p. 1179 - 1184
(2007/10/02)
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- Solvent Microstructure Effect on Reaction Stereochemistry; Ring Opening of Chalcone Oxides
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The stereochemistry and kinetics of acid-catalysed ring-opening reactions of epoxides are reported.Predominant inversion is found in the usual hydroxylic solvents.As the nucleophilicity of the solvent diminishes and acidity increases, the stereochemistry changes to predominant retention.Electron-donating substituents also tend to favour retention.In mixed solvents, the solvent microstructure is altered, leading to net retention for nucleophiles such as methanol.The exception is dioxane-methanol, which gives enhanced inversion.Molecular mechanics calculations indicate an electrostatic preference for the retention route, but a steric preference for inversion.The activation parameters indicate a negative entropy for both inversion and retention paths.Possible reasons are discussed for the entropy of the retention route being in the range normally found for A2 reactions.
- Durham, Dana,Kingsbury, Charles A.
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p. 923 - 930
(2007/10/02)
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