Enantio- and Diastereoselectivity in 1,3-Dipolar Cycloaddition Reactions of Nitrones with 3-Crotonoyl-2-oxazolidinone Catalyzed by Ni(II)- Binaphthyldiimine Complexes
| Autor: | Suketaka Ito, Akikazu Kakehi, Hiroyuki Suga, Hiroaki Sugimoto |
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| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Bulletin of the Chemical Society of Japan. 76:327-334 |
| ISSN: | 1348-0634 0009-2673 |
| DOI: | 10.1246/bcsj.76.327 |
| Popis: | Chiral Ni(II)-1,1′-binaphthyl-2,2′-diimine complexes were found to be effective Lewis-acid catalysts for an asymmetric 1,3-dipolar cycloaddition reaction of N-benzylideneaniline N-oxide with 3-crotonoyl-2-oxazolidinone. In the presence of molecular sieves (4 A), when the chiral N,N′-bis(2,6-dichlorobenzylidene)-1,1′-binaphthyl-2,2′-diamine (BINIM-DC) and Ni(ClO4)2·6H2O were used to prepare the catalyst, up to 81% ee of the corresponding endo-cycloadduct was obtained with endo-selectivity (87 : 13, and up to 96 : 4). The use of N,N′-bis(3-chloro-substituted 2-hydroxybenzylidene) derivatives as ligands under similar conditions showed high exo-selectivity (up to 95 : 5) with moderate enantioselectivity. Although almost no diastereoselectivity was observed, endo- and exo-cycloadducts were obtained with promising levels of enantioselectivity (up to > 98%) in the presence of catalysts, which were prepared from chiral BINIM-DC, NiBr2, and AgBF4, AgSbF6, or AgPF6. |
| Databáze: | OpenAIRE |
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