- Diastereoselective photocycloaddition reactions of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furans governed by chiral auxiliaries and hydrogen bonding interactions
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By using chiral auxiliaries and hydrogen bonding interactions, we have developed diastereoselective photocycloaddition of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furan derivatives. In photoreactions of (?)-menthyl 2-naphthalenecarboxylate with furan and 3-furanmethanol, respective maximum 48% and 40% diastereomeric excesses (d.e.) are observed. In photoreactions of di-8-phenyl-(?)-menthyl 2,3-naphthalenedicarboxylate with 3-furanmethanol, maximum 67% d.e. is obtained. Use of solvents of low polarity, low temperatures and low furan concentration leads to increased diastereoselectivities. Variable-temperature (VT) NMR and fluorescence quenching studies indicate that hydrogen bonding interactions between the carbonyl oxygen of naphthalenecarboxylic acid esters and the OH group in 3-furanmethanol take place in both the ground and excited states. The results of computational studies show that geometries of C2 symmetric naphthalenedicarboxylate reactants are important in governing the high diastereoselectivity in the photoreactions of 2,3-naphthalenedicarboxylates.
- Maeda, Hajime,Koshio, Norihiro,Tachibana, Yuko,Chiyonobu, Kazuhiko,Konishi, Gen-ichi,Mizuno, Kazuhiko
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- Asymmetric 1,2-Perfluoroalkyl Migration: Easy Access to Enantioenriched α-Hydroxy-α-perfluoroalkyl Esters
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This study has led to the development of a novel, highly efficient, 1,2-perfluoro-alkyl/-aryl migration process in reactions of hydrate of 1-perfluoro-alkyl/-aryl-1,2-diketones with alcohols, which are promoted by a Zn(II)/bisoxazoline and form α-perfluoro-alkyl/-aryl-substituted α-hydroxy esters. With (-)-8-phenylmenthol as the alcohol, the corresponding menthol esters are generated in high yields with excellent levels of diastereoselectivity. The mechanistic studies show that the benzilic ester-type rearrangement reaction takes place via an unusual 1,2-migration of electron-deficient trifluoromethyl group rather than the phenyl group. The overall process serves as a novel, efficient, and simple approach for the synthesis of highly enantioenriched, biologically relevant α-hydroxy-α-perfluoroalkyl carboxylic acid derivatives.
- Wang, Pan,Feng, Liang-Wen,Wang, Lijia,Li, Jun-Fang,Liao, Saihu,Tang, Yong
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p. 4626 - 4629
(2015/04/27)
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- Double asymmetric induction as a mechanistic probe: The doubly diastereoselective conjugate addition of enantiopure lithium amides to enantiopure α,β-unsaturated esters and enantiopure α,β-unsaturated hydroxamates
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The doubly diastereoselective conjugate addition of the antipodes of lithium N-benzyl-N-(α-methylbenzyl)amide to a range of enantiopure α,β-unsaturated esters [derived from Corey's 8-phenylmenthol chiral auxiliary] and enantiopure α,β-unsaturated hydroxamates [derived from our 'chiral Weinreb amide' auxiliary (S)-N-1-(1′-naphthyl)ethyl-O-tert- butylhydroxylamine] has been used as a mechanistic probe to determine the reactive conformations of these acceptors.
- Davies, Stephen G.,Lee, James A.,Roberts, Paul M.,Thomson, James E.,Yin, Jingda
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experimental part
p. 6382 - 6403
(2011/09/19)
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- Synthesis and Characterization of Enantiomerically Pure Menthylamines and Their Isocyanates
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A synthetic protocol for optically pure (-)-menthylamine, (-)-8-methylmenthylamine, and the novel (-)-8-phenylmenthylamine is presented including a detailed characterization of these compounds and their isocyanates.
- Schopohl, Matthias C.,Bergander, Klaus,Kataeva, Olga,Froehlich, Roland,Waldvogel, Siegfried R.
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p. 2689 - 2694
(2007/10/03)
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- Spiro Asymmetric Induction. 3. Synthesis of Optically Pure Syn or Anti α,β-Dihydroxy Esters by the Aldol Condensation of Chiral Glycolate Enolates
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The diastereoselectivity of the aldol condensation of the chiral glycolate enolates 1 and 2 is metaltunable, providing either syn or anti adducts 3-6.Ethanolysis of these adducts then provides any stereoisomer of the α,β-dihydroxy esters 7-10 in optically
- Pearson, William H.,Cheng, Minn-Chang
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p. 3176 - 3178
(2007/10/02)
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- REACTIONS OF STOICHIOMETRIC HIGHER ORDER, MIXED LITHIO MAGNESIO ORGANOCUPRATES
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Novel higher order cuprates, R(2-thienyl)Cu(CN)LiMgBr (2), are prepared from the 1:1:1 combination of CuCN, 2-lithiothiophene and RMgX.Reactions of various members of this new class of reagents are described, including substitution and conjugate addition processes, where the ligand derived from the Grignard reagent is selectively transferred.The effects of added BF3*Et2O are discussed.Some comparison reactions with the corresponding lower order reagents, RCu(CN)MgBr, have also been carried out.Evidence is presented suggesting that species 2, unlike their dilithio analogs, are not discrete.
- Lipshutz, Bruce H.,Parker, David A.,Nguyen, Sam L.,McCarthy, Keith E.,Barton, John C.,et al.
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p. 2873 - 2880
(2007/10/02)
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