排序方式: 共有12条查询结果,搜索用时 31 毫秒
1.
Tomohisa Yasuhara Katsumi Nishimura Ken-ichi Yamada Kiyoshi Tomioka 《Tetrahedron letters》2004,45(15):3043-3045
(±)-γ-Lycorane 3 was synthesized in 52% overall yield via seven steps from 5 by employing the highly stereoselective nitro-Michael cyclization of 5 to 9 and diastereoselective conjugate addition of aryllithium to a nitroolefin 10 as two key steps. 相似文献
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Alistair J.M. Farley Pavol Jakubec Anna M. Goldys Darren J. Dixon 《Tetrahedron》2018,74(38):5206-5212
Bifunctional iminophosphorane (BIMP) organocatalysts catalyze the enantio- and diastereoselective Michael additions of high pKa cyclic malonamate ester pro-nucleophiles to nitroalkenes with reactivity profiles of up to 3 orders of magnitude greater than tertiary amine bifunctional Brønsted base/(thio)urea organocatalysts. The unrivalled performance of the BIMPs allows reaction times of challenging reactions to be slashed from weeks to minutes and has enabled new flow chemistry applications using polystyrene-supported versions contained within a flow reactor. 相似文献
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The stereoselective synthesis of 7-oxanorbornane regarding as a key synthetic intermediate of tetrodotoxin (TTX) is reported. The bicyclo ring bearing various functional groups was successfully elaborated by a furan Diels–Alder (DA) reaction. The stereoselective installation of a quaternary amino carbon center to the DA product was achieved with the Tsuji–Trost allylation. The stereochemistry was unambiguously confirmed with X-ray. 相似文献
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Catalytic enantioselective Michael addition reactions of α-amino functionalized aldehydes to nitroolefins have been developed. The Michael product was obtained in up to 98% ee, but the enantiomeric purity of the Michael product was decreased during isolation of the product. 相似文献
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Stanisaw Zarzecki Janusz Zawadzki Wincenty Skupiski 《Reaction Kinetics and Catalysis Letters》2001,72(1):29-33
6-nitrohexene-1 (6-NH-1) undergoes metathesis in the presence of 16 wt.% Re2O7/Al2O3/R4M and 3 wt.% Re2O7/Al2O3-SiO2/R4M (where R = methyl, ethyl; M = Sn or Pb) catalysts. The system containing alumina as a support is more active. Tetramethyltin (TMT) and tetraethyllead (TEL) used as co-catalysts, exhibited similar activating effect which was greater than with tetraethyltin (TET). The best results were obtained when the Re:Sn(Pb) and 6-NH-1:Re ratios were equal, respectively, to 1:1 and 10:1. The alumina-silica supported catalysts activity can be enhanced by doping the support with very small amounts of molybdenum ions. 相似文献
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Jia-Rong Chen 《Tetrahedron》2010,66(29):5367-5372
Asymmetric Michael addition reactions of aldehydes to nitroolefins have been successfully initiated by a series of primary amine thiourea bifunctional catalysts, with high enantioselectivities (90-98% ee) and excellent yields (80-96%). The privileged quinine scaffold was found to be essential to the reaction efficiency and enantioselectivity. 相似文献
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Michael addition of thiols to nitroolefins was carried out in water at room temperature without any catalyst, and β-nitro sulfides were obtained in excellent yields. This is the first example of Michael addition of thiols to nitroolefins in water without use of any catalyst. It provides a highly efficient, general, and practical green route to synthesis of β-nitro sulfides. Twenty-four new β-nitro sulfides were synthesized using this technique. 相似文献
10.
Fanny Valleix 《Tetrahedron》2005,61(31):7420-7424
The copper-amidophosphane-catalyzed asymmetric addition reaction of dialkylzinc reagents with β-aryl and β-alkylnitroalkenes afforded the corresponding nitroalkanes with moderate to good enantioselectivities (54-80% ee). The performance was highly dependent on the reaction procedure where the addition of nitroalkene to the mixture of copper-amidophosphane and dialkylzinc gave higher ee than the addition of dialkylzinc to a mixture of copper-amidophosphane and nitroalkene. 相似文献