700871-34-7Relevant articles and documents
Facile and rapid immobilization of copper(II) bis(oxazoline) catalysts on silica: Application to Diels-Alder reactions, recycling, and unexpected effects on enantioselectivity
O'Leary, Patrick,Krosveld, Nico P.,De Jong, Krijn P.,Van Koten, Gerard,Klein Gebbink, Robertus J. M.
, p. 3177 - 3180 (2004)
Two chiral copper(II) bis(oxazoline) complexes have been immobilized on silica via electrostatic interactions using a remarkably straightforward procedure. The immobilized catalysts were tested in a standard Diels-Alder reaction and gave surprising results. Where the immobilized Cu((S,S)-phenyl-box) (OTf)2 catalyst was used, the predominant enantiomer formed was the opposite of that produced using the same catalyst in a homogeneous reaction. This is a startling result given that the only difference is the electrostatic immobilization of the catalyst on amorphous silica. The activity of the catalyst in a hetero Diels-Alder reaction was also tested. This catalyst was also recycled, successfully maintaining a similar activity to the homogeneous analogue through a number of cycles.
Exo-selective asymmetric inverse-electron demand hetero-diels-alder reaction catalyzed by Cu(II)-hydroxy oxazoline ligands
Barba, Andrea,Barroso, Santiago,Blay, Gonzalo,Cardona, Luz,Melegari, Martina,Pedro, José R.
experimental part, p. 1592 - 1596 (2011/08/03)
Cu(II) complexes of hydroxy oxazolines derived from (+)-(S)-ketopinic acid catalyze the asymmetric hetero-Diels-Alder cycloaddition of enol ethers and ,-unsaturated -keto esters. The reaction takes place with unprecedented exo selectivity providing 2,4-trans-disubstituted chiral 2,3-dihydropyrans with up to 88% ee. Georg Thieme Verlag Stuttgart ? New York.
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.
Highly enantioselective catalytic hetero-diels-alder reaction with inverse electron demand
Thorhauge, Jacob,Johannsen, Mogens,Jorgensen, Karl Anker
, p. 2404 - 2406 (2007/10/03)
Valuable substrates for the synthesis of natural products, compounds 3 (R1 = alkyl, aryl, alkoxy; R2, R3 = alkyl) are formed from β,γ-unsaturated α-keto esters 1 and vinyl ethers 2 by the title reaction [Eq. (1)]. Copper(II) bisozaxolines act as catalysts, and in many cases enantiomeric excesses higher than 99.5% are achieved.
