- D-Penicillamine and L-cysteine derived thiazolidine catalysts: an efficient approach to both enantiomers of secondary alcohols
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D-Penicillamine derived thiazolidine ligands were prepared in a two-step synthetic sequence and used in the enantioselective alkylation of a variety of aromatic aldehydes with diethylzinc at room temperature. Excellent ee, up to >99%, and nearly complete conversions were observed. Structurally analogous L-cysteine derived thiazolidine ligands were also synthesized and tested for comparative purposes, resulting in very good, albeit slightly lower selectivities, up to 89%. The combined use of these two types of thiazolidines constitutes a very interesting strategy for synthesizing both (S) and (R) enantiomers of chiral secondary alcohols, thus leading the way to a myriad of useful optically active products with opposite absolute configurations.
- Serra, M. Elisa Silva,Costa, Dora,Murtinho, Dina,Tavares, Nélia C.T.,Pinho e Melo, Teresa M.V.D.
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- Modular chiral thiazolidine catalysts in asymmetric aryl transfer reactions
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Modular chiral thiazolidine derivatives were synthesized in a single step from inexpensive and commercially available starting materials. These ligands catalyzed enantioselective arylation of different aldehydes using aryl boronic acids as a source of transferable aryl groups. The products were obtained in excellent yields and good enantioselectivities.
- Braga, Antonio Luiz,Milani, Priscila,Vargas, Fabricio,Paixao, Marcio W.,Sehnem, Jasquer A.
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p. 2793 - 2797
(2007/10/03)
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- Novel thiazolidine derivatives as chiral catalysts in the enantioselective addition of diethylzinc to aldehydes
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New chiral thiazolidine derivatives were synthesized conveniently from natural L-cysteine and showed good enantioselectivity (up to 90% ee) in the addition of diethylzinc to aldehydes. The catalytic efficiency of the thiazolidine derivatives is influenced by the different structures of the thiazolidine rings and the bulkiness of R moiety in the ester groups. (C) 2000 Elsevier Science Ltd.
- Meng, Qinglin,Li, Yuelan,He, Yan,Guan, Yedi
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p. 4255 - 4261
(2007/10/03)
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- The steric effect and enantioselectivity of chiral 2,2-disubstituted thiaprolinol derivatives as ligands for borane reduction of aromatic ketones and for diethylzinc addition to aromatic aldehydes
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A new series of chiral amino alcohols 3a-e has been prepared from natural amino acid L-cysteine. These compounds have been used as chiral ligands for borane reduction of ketones and for diethylzinc addition to aldehydes. In the reduction of ketones, 3b-e have been used as the substitute of (R)-prolinol to provide (S)-alcohols in good yields had modest enantioselectivity (30-50% ee). In the diethylzinc addition to aldehydes, 3b-e promoted the formation of (S)-alcohols in excellent yields and medium to good enantioselectivities (60-80% ee). Copyright (C) 1996 Published by Elsevier Science Ltd.
- Huang, Hsiang-Ling,Lin, Ya-Chuan,Chen, Shyh-Fong,Wang, Chia-Lin J.,Liu, Lee Tai
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p. 3067 - 3070
(2007/10/03)
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