207846-60-4Relevant academic research and scientific papers
Chiral C2-symmetric Cu(II) complex immobilized in ionic liquids: A recoverable catalytic system for enantioselective hetero-Diels-Alder reaction
Yong, Je Shin,Yeom, Chang-Eun,Mi, Jeong Kim,Kim, B. Moon
, p. 89 - 93 (2008)
Hydrophobic ionic liquids such as [Bmim]PF6 and [Bmim]SbF 6 were used successfully as powerful media for bis(oxazoline)-copper- catalyzed asymmetric hetero-Diels-Alder reactions. The reactivities and stereoselectivities were comparable (endo/exo up to 97:3 and up to 94% ee, respectively) to those of the corresponding homogeneous reactions. Furthermore, the reaction was remarkably accelerated in [Bmim]PF6 compared to that in dichloromethane at 3 (±1)°C and metal-ligand complexes were recovered and recycled up to eight times exhibiting almost the same reactivity and selectivity. Georg Thieme Verlag Stuttgart.
Enantioselective synthesis of dihydropyrans. Catalysis of hetero Diels - Alder reactions by bis(oxazoline) copper(II) complexes
Evans, David A.,Johnson, Jeffrey S.,Olhava, Edward J.
, p. 1635 - 1649 (2007/10/03)
C2-symmetric bis(oxazoline) - Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels - Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity, α,β- Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function as heterodienophiles. A range of substitution patterns is possible on the heterodiene: terminal alkyl, aryl, alkoxy, and thioether substituents are all tolerated. The enantioselective synthesis of dihydropyrans by this method has been shown to be straightforward: cycloadditions may be conducted with as little as 0.2 mol % of the chiral catalyst and are readily run on multigram scale. The reactions exhibit a favorable temperature - enantioselectivity profile, with selectivities exceeding 90% even at room temperature. A simple reaction protocol that employs a solid air-stable catalyst, convenient reaction temperatures, and low catalyst loadings is described. The utility of the derived cycloadducts in the preparation of chiral building blocks is demonstrated. Models for asymmetric induction are discussed considering product stereochemistry, X-ray crystallographic data for the solid catalysts, and mechanistic studies.
