908253-01-0Relevant articles and documents
New chiral zwitterionic phosphorus heterocycles: Synthesis, structure, properties and application as chiral solvating agents
Sheshenev, Andrey E.,Boltukhina, Ekaterina V.,Grishina, Anastasiya A.,Cisa?ova, Ivana,Lyapkalo, Ilya M.,Hii, King Kuok
, p. 8136 - 8143 (2013)
A family of new chiral zwitterionic phosphorus-containing heterocycles (zPHC) have been derived from methylene-bridged bis(imidazolines). These structures were unambiguously determined, including single-crystal XRD analysis for two compounds. The stability, acid/base and electronic properties of these dipolar phosphorus heterocycles were subsequently investigated. zPHCs can be successfully employed as a new class of chiral solvating agents for the enantiodifferentiation of chiral carboxylic and sulfonic acids by NMR spectroscopy. The stoichiometry and binding constants for the donor-acceptor complexes formed were established by NMR titration methods. A convenient synthetic approach to a new class of chiral zwitterionic phosphorus-containing heterocycles starting from methylene-bridged bis(imidazolines) was designed and executed. Stability and properties of the synthesized compounds were investigated. The applicability of the designed compounds as chiral solvating agents for the determination of the enantiomeric excesses of chiral acids was demonstrated. Copyright
Methylene-bridged bis(imidazoline)-derived 2-oxopyrimidinium salts as catalysts for asymmetric Michael reactions
Sheshenev, Andrey E.,Boltukhina, Ekaterina V.,White, Andrew J. P.,Hii, King Kuok
supporting information, p. 6988 - 6991 (2013/07/25)
In nothing flat: The title salts, having planar nitrogen centers, were utilized successfully as phase-transfer catalysts for asymmetric Michael reactions of tert-butyl glycinate benzophenone Schiff base with vinyl ketone and chalcone derivatives, thus providing excellent levels of diastereo- and enantiocontrol (see scheme). Copyright
Reversal of selectivity in acetate aldol reactions of N-acetyl-(S)-4- isopropyl-1-[(R)-1-phenylethyl]imidazolidin-2-one
Khatik, Gopal L.,Kumar, Varun,Nair, Vipin A.
, p. 2442 - 2445 (2012/07/03)
Synergistic effects of the exo- and endocyclic chiral centers of an imidazolidinone-based auxiliary were investigated in the perspective of acetate aldol reactions. The reversal in diastereoselectivity was accomplished by lithium and titanium enolate reactions, which proceed through proposed open and closed transitions states, respectively. The aldol adducts were used in the stereoselective synthesis of fluoxetine.
Chiral calcium catalysts for asymmetric hydroamination/cyclisation
Wixey, James S.,Ward, Benjamin D.
, p. 5449 - 5451 (2011/06/28)
Calcium complexes supported by chiral 1,2-diamines have been shown to be efficient catalysts for the asymmetric hydroamination of amino-olefin substrates; the calcium complexes [Ca(NNR){N(SiMe3) 2}(THF)] (R = tBu, iPr, Ph, 4-C 6H4F) give enantioselectivities of up to 26% which marks a significant increase based upon literature precedence. The structure of [Ca(NNPh){N(SiMe3)2}(py)] has been computed with density functional methods.
Design of chiral hydroxyalkyl- and hydroxyarylazolinium salts as new chelating diaminocarbene ligand precursors devoted to asymmetric copper-catalyzed conjugate addition
Rix, Diane,Labat, Stephane,Toupet, Loic,Crevisy, Christophe,Mauduit, Marc
scheme or table, p. 1989 - 1999 (2009/10/30)
The design and the synthesis of a set of new chiral hy- droxyalkyl- and hydroxyaryl-chelating diaminocarbene ligands is reported. Comparative catalytic studies show the importance of the scaffold design around the NHC unit to obtain a high enantiocontrol in Cu-catalyzed asymmetric conjugate addition (ACA). Whereas low selectivities are observed when the stereogenic centre is placed within the N-heterocyclic ring, an interesting match effect can be observed when central chirality is located within both of the two side chains, which enables up to 92 % ee in the catalysis reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009.
Chiral pyridine imidazolines from C1-symmetric diamines: Synthesis, arene ruthenium complexes and application as asymmetric catalysis for Diels-Alder reactions
Davenport, Adam J.,Davies, David L.,Fawcett, John,Russell, David R.
, p. 3445 - 3450 (2007/10/03)
Condensation of mono N-substituted chiral ethylenediamines and pyridine-2-methoxyimidate gives new chiral pyridine imidazolines (1a-c). These react with [RuCl2(mes)]2 (mes = 1,3,5-trimethyl benzene) in the presence of NaSbF6 to give complexes [RuCl(L)(mes)][SbF6] (5a-c) which after treatment with AgSbF6 are enantioselective catalysts for the Diels-Alder reaction of methacrolein and cyclopentadiene. The imidazoline catalysts are less selective than the corresponding oxazoline ones. Compounds 1a, 5b and 5c have been characterised by X-ray crystallography.
