one-pot, two-step process was disclosed for production of chiral α,β-epoxy ketonesfrom benzaldehydes and acetophenones catalyzed by imidazolium-modified poly(l-leucine). Two effective reaction systems with complementary high enantioselectivities (up to 98% ee) or satisfactory yields (up to 89%) have been developed. Importantly, the poly(aminoacid) catalyst can be easily recovered and recycled for ten
Syntheses, Structures, and Catalytic Activities of the Anionic Heterobimetallic Rare-Earth Metal Complexes Supported by Pyrrolyl-Substituted 1,2-Diimino Ligands
rare-earth metal complexes (L3)2RELi(THF)2 (RE = Pr (11), Sm(12), Eu(13)). Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with 2 equiv of (R,R)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane (H2L4) also gave the heterobimetallic rare-earth metal complexes (L4)2RELi(THF)2 (Ln = Pr(14), Sm(15)). All complexes were characterized by spectroscopic methods and elemental analyses, and complexes 5–11, 13, and 14
A highly efficient catalytic kinetic resolution of 2,3-epoxy 3-aryl ketones via asymmetric ring-opening with pyrazole derivatives has been achieved by using a chiral N,N′-dioxide–Sc(iii) complex as the catalyst.
Abstract New recyclable monoaza-15-crown ethers have been synthesized starting from ( R , R )-(+)- and ( S , S )-(−)-hydrobenzoin. These macrocycles proved to be efficient and reusable phase transfer catalysts in a few asymmetric reactions under mild conditions. The asymmetric epoxidation of trans -chalcone took place with up to 81% ee, while using other chalcone derivatives, the products were formed
摘要 以 ( R , R )-(+)- 和 ( S , S )-(-)- 氢安息香为原料合成了新的可回收单氮杂-15-冠醚。在温和条件下的一些不对称反应中,这些大环被证明是有效且可重复使用的相转移催化剂。反式查耳酮的不对称环氧化反应的 ee 高达 81%,而使用其他查耳酮衍生物时,生成的产物 ee 高达 68-88%。还使用溴丙二酸二乙酯在一些缺电子烯烃的环丙烷化中测试了基于氢安息香的套索醚,以提供具有良好对映选择性(54-75% ee)的产物。催化剂通过成盐回收,然后萃取,并在不损失活性和对映选择性影响的情况下重复使用。
Enantioselective epoxidation of α,β-enones promoted by (1R,3S,4S)-2-azanorbornyl-3-methanol as an organocatalyst
作者:Jun Lu、Yun-He Xu、Feng Liu、Teck-Peng Loh
DOI:10.1016/j.tetlet.2008.07.175
日期:2008.10
(1R,3S,4S)-2-Azanorbornyl-3-methanol was synthesized form (R)-1-phenylethylamine and used as a catalyst for the enantioselectiveepoxidation of α,β-enones to afford the corresponding epoxides in good yields and high enantioselectivities at room temperature.