- Diastereoselective Electrophilic Trifluoromethylthiolation of Chiral Oxazolidinones: Access to Enantiopure α-SCF3 Alcohols
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Lithium imide enolates featuring Evans’ chiral oxazolidinone auxiliary were involved in diastereoselective α-trifluoromethylthiolation with electrophilic SCF3 donors. Diastereopure products were isolated and converted to enantiopure α-SCF3 alcohols without racemisation. (Figure presented.).
- Chachignon, Hélène,Kondrashov, Evgeniy V.,Cahard, Dominique
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supporting information
p. 965 - 971
(2018/01/27)
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- Synthesis of α-CF3-substituted carbonyl compounds with relative and absolute stereocontrol using electrophilic CF3-transfer reagents
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Evans-type chiral lithium imide enolates undergo diastereoselective α-trifluoromethylation with a hypervalent iodine-CF3 reagent with up to 91% combined isolated yield and 97:3 dr. The resulting isolated diastereopure products can be further transformed into valuable products without racemization.
- Matousek, Vaclav,Togni, Antonio,Bizet, Vincent,Cahard, Dominique
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supporting information; experimental part
p. 5762 - 5765
(2012/01/06)
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- Diastereoselective Electrochemical Carboxylation of Chiral α-Bromocarboxylic Acid Derivatives: An Easy Access to Unsymmetrical Alkylmalonic Ester Derivatives
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The diastereoselective electrochemical carboxylation of chiral N-(2-bromoacyl)oxazolidin-2-ones has been studied. This reaction was carried out by cathodic reduction of the C - Br bond, in the presence of carbon dioxide, followed by treatment with diazomethane. The yields and the diastereomeric ratio of the two epimeric alkylmalonic acid derivatives are strongly affected by various factors: solvent-supporting electrolyte system, temperature, electrode material, electrolysis conditions, oxazolidinone moiety. The higher yields (88%) were obtained starting from N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one la, but with poor diastereoselectivity (61:39). The two epimers were easily separated by flash chromatography. The best results were achieved using a different chiral auxiliary: Oppolzer's camphor sultam. Starting from 1j a good yield in carboxylated product was obtained (80%) with excellent diastereoselectivity (98:2). These chiral alkylmalonic acid derivatives are valuable building blocks in the synthesis of molecules with biological activity and of chiral propane-1,3-diols derivatives.
- Feroci, Marta,Orsini, Monica,Palombi, Laura,Sotgiu, Giovanni,Colapietro, Marcello,Inesi, Achille
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p. 487 - 494
(2007/10/03)
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- A convenient method for synthesis of optically active methylphenidate from N-methoxycarbonylpiperidine by utilizing electrochemical oxidation and Evans aldol-type reaction
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A new method to prepare optically active methylphenidate starting from piperidine is described. The method consists of a transformation of N-methoxycarbonylated piperidine to the corresponding α-methoxylated carbamate utilizing electrochemical oxidation f
- Matsumura, Yoshihiro,Kanda, Yasuhisa,Shirai, Kimihiro,Onomura, Osamu,Maki, Toshihide
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p. 7411 - 7422
(2007/10/03)
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- A convenient and practical method for N-acylation of 2 oxazolidinone chiral auxiliaries with acids
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A one-pot, convenient and practical method for N-acylation of 2- oxazolidinone chiral auxiliaries directly with acids in the presence of pivaloyl chloride and triethylamine is described.
- Prashad, Mahavir,Kim, Hong-Yong,Har, Denis,Repic, Oljan,Blacklock, Thomas J.
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p. 9369 - 9372
(2007/10/03)
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- Asymmetric synthesis of optically active 2,3-diarylsuccinic acids by oxidative homocoupling of chiral 3-(arylacetyl)-2-oxazolidones
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Oxidative homocoupling of chiral 3-(arylacetyl)-2-oxazolidones 1 was achieved by treatment with DABCO-TiCl4 or DMAP-TiCl4 and afforded the corresponding dimers stereospecifically. The reaction of (4S)- and (4R)-substituted 1 gave (S,S)- and (R,R)-dimers respectively. The obtained dimers were easily transformed to the corresponding 2,3-diaryl succinic acids. This reaction therefore provides a useful method For the synthesis of optically pure 2,3-diarylsuccinic acids. The oxidative coupling was not inhibited by para substitution of an electron donating group on the aryl group. A para-substituted electron withdrawing group and an ortho-substituent, however, hindered the coupling.
- Kise, Naoki,Kumada, Kimikage,Terao, Yuichi,Ueda, Nasuo
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p. 2697 - 2708
(2007/10/03)
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