- Benchtop-Stabssle Hypervalent Bromine(III) Compounds: Versatile Strategy and Platform for Air- And Moisture-Stable λ3-Bromanes
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We present the first synthesis of air/moisture-stable λ3-bromanes (9and10) by using a cyclic 1,2-benzbromoxol-3-one (BBX) strategy. X-ray crystallography and NMR and IR spectroscopy ofN-triflylimino-λ3-bromane (12) revealed that the bromine(III) center is effectively stabilized by intramolecular R-Br-O hypervalent bonding. This strategy enables the synthesis of a variety of air-, moisture-, and benchtop-stable Br-hydroxy, -acetoxy, -alkynyl, -aryl, and bis[(trifluoromethyl)sulfonyl]methylide λ3-bromane derivatives.
- Miyamoto, Kazunori,Saito, Motomichi,Tsuji, Shunsuke,Takagi, Taisei,Shiro, Motoo,Uchiyama, Masanobu,Ochiai, Masahito
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supporting information
p. 9327 - 9331
(2021/07/01)
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- A highly enantioselective asymmetric Darzens reaction catalysed by proline based efficient organocatalysts for the synthesis of di- and tri-substituted epoxides
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A new class of easily available and readily tunable proline based chiral organocatalysts was found to efficiently catalyse an unprecedented highly enantioselective asymmetric Darzens reaction of α-chloroketones and substituted α-chloroketones with various
- Ashokkumar, Veeramanoharan,Siva, Ayyanar,Ramaswamy Chidambaram
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supporting information
p. 10926 - 10929
(2017/10/13)
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- Convenient methods for the preparation of unsymmetrical double aldols
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Double aldol reaction proceeded stereoselectively at one α-carbon of ketones to give α-(1-hydroxyalkyl)-β-hydroxyalkyl ketones (double aldols) in good to high yields by the following three methods: i) tin(II) trifluoromethanesulfonate-mediated aldol reaction of aldehydes with β-hydroxy ketones (mono-aldols) in the presence of tertiary amines, ii) samarium(II) iodide-mediated aldol reaction of aldehydes with alkyl or aryl oxiranyl ketones, iii) Sn(OTf)2- promoted aldol reaction of α-bromo ketones with aldehydes giving α-bromo-β-stannyloxy ketones which were then converted to titanium enolates on treatment with low-valent titanium. Double aldols were formed by subsequent reaction of the above titanium enolates with aldehydes in one-pot procedure. Further, small and medium-sized carbocyclic compounds whose ring skeletons were composed of double aldol structure were synthesized by SmI2-mediated intramolecular cyclization between oxiranyl ketone and aldehyde functions.
- Mukaiyama, Teruaki,Pudhom, Khanitha,Yamane, Keiko,Arai, Hidehiro
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p. 413 - 425
(2007/10/03)
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- Unprecedented direct oxygen atom transfer from hypervalent oxido-λ3-iodanes to α,β-unsaturated carbonyl compounds: Synthesis of α,β-epoxy carbonyl compounds
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Tetra-n-butylammonium oxido-λ3-iodane, prepared from 1-hydroxy-1,2-benziodoxol-3(1H)-one by reaction with tetra-n-butylammonium fluoride, directly undergoes oxygen atom transfer to γ,β-unsaturated carbonyl compounds, yielding epoxides.
- Ochiai, Masahito,Nakanishi, Akinobu,Suefuji, Takashi
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p. 2923 - 2926
(2007/10/03)
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- NMR studies of three types of highly coordinated organotin hydrides: Chemo-, regio-, and stereoselective reduction of 2,3-epoxy ketones
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Three types of highly coordinated organotin hydrides, Bu2SnIH-Lewis base (Lewis bases; HMPA or tripiperidinophosphine oxide) (type A), Bu2SnFH-HMPA (type B), and Bu3SnH-Bu4NX (X = F, CN) (type C), were characterized as nucleophilic, chelation, and nonchelation types of reductants, respectively, in the reaction with 2,3-epoxy ketones 1. These reagents, which promoted a reduction of the epoxy ring and syn-selective and anti-selective carbonyl reduction, respectively, were spectroscopically confirmed with 1H, 13C, 19F, and 119Sn NMR and FT-IR. Furthermore, the correlations between their structures and selective reducing abilities were discussed.
- Kawakami, Takayo,Shibata, Ikuya,Baba, Akio
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- Baker's Yeast-mediated Transformations of α-Keto Epoxides
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αβ-Epoxy ketones on treatment with baker's yeast yield different types of products depending on their substitution.Small groups such as H or Me attached at the epoxy end protect that end from attack.Thus,1-acyl epoxides with H, methyl or propyl as the 2-e
- Meth-Cohn, Otto,Horak, R. Martinus,Fouche, Gerda
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p. 1517 - 1528
(2007/10/02)
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- Enzymatic Synthesis of Chiral 1-Phenyl-1,2- and 1,3-diols via Chiral Epoxy Alcohols
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Chiral epoxy alcohols have been prepared by asymmetric reduction of 1-phenyl-2,3-epoxybutan-1-one with baker's yeast, or by enantioselective esterification of racemic 1-phenyl-2,3-epoxybutan-1-one with lipase PS.The epoxyalcohols obtained were reduced with lithium aluminium hydride to afford chiral 1-phenylbutane-1,2- and 1,3-diols.The absolute configurations of the epoxy alcohols and diols were determined by use of modified Mosher's method or by comparison with the diols, which were prepared from benzoylacetone via chiral enols by use of baker's yeast and lipase PS.
- Takeshita, Mitsuhiro,Miura, Masatomo,Unuma, Yukiko
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p. 2901 - 2906
(2007/10/02)
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- Ttimethylsilyl Cyanide - A Reagent for Umpolung, XVIII. - Nucleophilic Acylation of α-Chlorocarbonyl Compounds - a Novel and Diastereoselective Approach to Substituted α,β-Epoxy Ketones
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The addition products of trimethylsilyl cyanide and benzaldehyde (1a), furfural (1b), and α,β-unsaturated aldehydes 2a-c, respectively, react after deprotonation with α-chloroaldehydes and -ketones 3a-d.By 1,4-O,O-silyl rearrangement and cyanide elimination O-trimethylsilyl acyloins 4 and 9, respectively, are formed.With fluoride, 4 and 9 react to α,β-epoxy ketones 5 and 10 in high yield and with E/Z selectivities from 80:20 to >95:5.By this novel route even α,β-unsaturated epoxy ketones (10) become available.
- Huenig, Siegfried,Marschner, Claus
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p. 107 - 114
(2007/10/02)
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- Enantioselective Diastereospecific Synthesis of anti-α-Alkyl-β-hydroxy Esters through Cuprate Opening of Glycidic Esters
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A diastereospecific chain elongation of the aldehydes 1 to anti-αalkyl-β-hydroxy esters 2 via the intermediates 4 - 7 is described.By means of the Sharpless epoxidation, 2 may be obtained with >90percent ee in either enantiomer.
- Mulzer, Johann,Lammer, Ortrud
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p. 2178 - 2190
(2007/10/02)
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- SELECTIVE OXIDATION WITH t-BUTYL HYDROPEROXIDE AND ALUMINIUM REAGENTS
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Stereoselective epoxidation of allylic alcohols is achieved with organoaluminium peroxides.Transformation of secondary alkohols to ketones with same reagents is also disclosed.
- Takai, Kazuhiko,Oshima, Koichiro,Nozaki, Hitosi
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p. 1657 - 1660
(2007/10/02)
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