- Amberlyst-15: A reusable heterogeneous catalyst for the dehydration of tertiary alcohols
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Tertiary alcohols react under mild conditions in the presence of Amberlyst-15 (dry) (solid-supported sulfonic acid) to give predominantly the most stable alkene in very good yield. The dehydration of tertiary alcohol functionality occurs without observation of rearrangement and polymerization products, and with outstanding substrate tolerance, which include the NHCBz, NHBoc, OSEM, OTBDMS, OBOM and ethylene ketal functional groups. Amberlyst-15 (dry) can be easily recovered from the reaction medium and reused for five cycles, maintaining the catalytic efficiency. In addition, the dehydration can occur under continuous operation.
- Frija, Luís M.T.,Afonso, Carlos A.M.
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experimental part
p. 7414 - 7421
(2012/09/22)
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- Ligand effects on diastereoselective addition of organocerium reagents to aldehydes and cyclic ketones
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A new class of chiral dialkoxy- and diaryloxyorganocerium reagent has been prepared and the diastereoselectivity of carbonyl addition reactions has been compared with that of conventional organocerium reagents.
- Greeves, Nicholas,Lyford, Lisa,Elizabeth Pease
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p. 285 - 288
(2007/10/02)
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- Unprecedented Stereoselectivity in the Addition of Organoiron(II) Reagents to Cyclohaxanone Derivatives
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Various organoiron(II) reagents undergo Grignard-type additions to substituted cyclohexanone derivatives, C-C bond formation occurring stereoselectively from the equatorial direction (97 - 100percent selectivity).
- Reetz, Manfred T.,Stanchev, Stephan
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p. 328 - 330
(2007/10/02)
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- Ligand effects in selective carbonyl addition reactions of organomanganese and cerium reagents
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Transmetalation of organolithium reagents RLi (R = CH3, n-Bu) with manganese pivalate produces reagents of the type RMnOC(O)tBu which react stereoselectively with substituted cyclohexanones to afford the axial alcohols preferentially. These rea
- Reetz, Manfred T.,Haning, Helmut,Stanchev, Stephan
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p. 6963 - 6966
(2007/10/02)
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- Amphiphilic Reactions by Means of Exceptionally Bulky Organoaluminum Reagents. Rational Approach for Obtaining Unusual Equatorial, Anti-Cram, and 1,4 Selectivity in Carbonyl Alkylation
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Exceptionally bulky, oxygenophilic organoaluminum reagents, methylaluminum bis(2,6-di-tert-4-alkylphenoxide) (MAD and MAT), have been successfully utilized for stereoselective activation of carbonyl moiety.Combination of MAD or MAT with carbon nucleophiles such as organolithiums or Grignard reagents generates a new amphiphilic reaction system in which the alkylation may be interpreted as the nucleophilic addition of a reactive organometallic compound to an electrophilically activated carbonyl substrate in order to account for the regio- and stereochemical consequences.In contrast to the ordinary alkylations, the amphilic alkylation disclosed herein would be categorized into the new, yet unexplored class of alkylation that exhibits high chemoselectivity to carbonyl compounds, and more significantly it allows excellent equatorial and anti-Cram selectivity in carbonyl alkylations, hitherto difficult by the existing methodologies.Further, unusual conjugate addition of organolithium reagents to α,β-unsaturated carbonyl compounds has been accomplished by using the amphiphilic reaction system.
- Maruoka, Keiji,Itoh, Takayuki,Sakurai, Minoru,Nonoshita, Katsumasa,Yamamoto, Hisashi
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p. 3588 - 3597
(2007/10/02)
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- The evaluation of dicyclopentadienylsamarium as a reagent in organic synthesis
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SmCp2, which is easily prepared from SmI2, has been screened as a reducing agent for organic chemistry. In particular, SmCp2 promotes the pseudo-Barbier reaction between carbonyl compounds (aldehydes and ketones) and aliphatic or allylic halides more efficiently than does SmI2.
- Namy,Collin,Zhang,Kagan
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