Showing papers by "Emmanuelle Schulz published in 2008"
TL;DR: New chiral binaphthylamido yttrium and ytterbium ate complexes with lithium and potassium counterions have been synthesised and characterised and the most active catalyst, [Li(thf)4], was successfully used for the cyclisation of aminopentenes with internal double bonds.
Abstract: New chiral binaphthylamido yttrium and ytterbium ate complexes with lithium and potassium counterions have been synthesised and characterised. X-ray structures have been obtained for [Li(thf)4][Ln{(R)-C20H12(NC5H9)2}2] (Ln=Yb, Y) and [K(thf)5][Yb{(R)-C20H12(NCH2CMe3)2}2] as isostructural complexes. The efficiency of these complexes for the enantioselective intramolecular hydroamination was examined. [Li(thf)4][Yb{(R)-C20H12(NC5H9)2}2] afforded the highest enantiomeric excess (up to 87 %) for the synthesis of a spiropyrrolidine, while [Li(thf)4][Y{(R)-C20H12(NC5H9)2}2] proved to be slightly more active. The role of the counter cation in the active catalytic species was evidenced by the comparison between lithium and potassium ate complexes. The most active catalyst of this series, [Li(thf)4][Yb{(R)-C20H12(NCH2CMe3)2}2], was successfully used for the cyclisation of aminopentenes with internal double bonds.
100 citations
TL;DR: New chiral binaphthylamido alkyl ate and neutral yttrium and ytterbium complexes have been synthesized and characterized X-ray structures have been obtained as discussed by the authors.
62 citations
TL;DR: A facile method for the preparation of highly active and enantioselective yttrium precatalysts for asymmetric hydroamination of gem-disubstituted aminoalkenes from the combination of YCl(3) or YCl (3)(THF)(3.5) with ligand (R)- and n-BuLi is described.
51 citations
TL;DR: In this article, the highly constrained, axially chiral atropos diamines (R,S,S)-1, (Ri,R,R)-1 and their tropos analogue diamines 2 have been prepared via bis-N,N-dialkylation of (R)-2,2′-diamino-1,1′-binaphthyl.
Abstract: The highly constrained, axially chiral atropos diamines (Ri,S,S)-1, (Ri,R,R)-1 and (Ri,S,R)-1 and their tropos analogue (Ri)-2 have been prepared via bis-N,N-dialkylation of (R)-2,2′-diamino-1,1′-binaphthyl, using either (R)- or (S)-2,2′-bis(bromomethyl)-1,1′-binaphthyl and 2,2′-bis(bromomethyl)-1,1′-biphenyl as alkylating agents, followed by selective nickel chloride-catalysed bis(mono-hydrogenolysis) of the tertiary amino groups of the so-obtained (Ri,R,R)-4, (Ri,S,S)-4, (Ri,R,S)-4 and (Ri)-6, respectively, by lithium aluminium hydride in refluxing THF or THF/diglyme. The diamines (Ri,S,S)-1, (Ri,R,R)-1, (Ri,S,R)-1 and (Ri)-2 have been evaluated as ligands for ytterbium-catalysed intramolecular hydroamination and compared to the ligand 1,1′-binaphthyl-2,2′-bis(benzylamine) (Ri)-3. They afforded highly active catalysts for the cyclisation of aminopentenes and aminohexenes with up to 58% ee.
44 citations
TL;DR: In this paper, a chiral thiophene-salen ligand was synthesized and the corresponding chromium complexes proved to be efficient catalysts for promoting asymmetric hetero-Diels-Alder reactions with good activities and high enantioselectivities.
41 citations
TL;DR: In this paper, a new concept is proposed for ultradeep desulfurization of straight run gas oil (SRGO) with various sulfur contents (390 and 60 ppm S).
Abstract: Adsorptive desulfurization was studied using straight-run gas oil (SRGO) with various sulfur contents (390 and 60 ppm S). Immobilization of electron-poor molecules (π-acceptors) on macroporous resins was achieved in three steps starting from commercially available poly(styrene-co-divinylbenzene) beads. Influence of the temperature on adsorption was studied, and the process was examined on the basis of breakthrough curves. The regeneration of the support was studied using fixed-bed technology and was efficiently performed with toluene as the solvent. The extracted compounds were easily recovered after evaporation of the toluene and the affinity of the resins toward alkyldibenzothiophenes was confirmed by GC-FPD analysis. On the basis of these preliminary experimental results, a new concept is proposed for ultradeep desulfurization of SRGO.
19 citations
TL;DR: In this article, the first examples of assembling monodentate oxazoline donor and acceptor ligands by charge transfer interactions are described to mimic bidentate ligands in asymmetric catalysis.
Abstract: The first examples of assembling monodentate oxazoline donor and acceptor ligands by charge transfer interactions are described to mimic bidentate ligands in asymmetric catalysis. The corresponding copper(II) complexes were used in an enantioselective Diels–Alder reaction and showed very high efficiency, but only moderate stereoselectivity. These complexes were successfully recovered and reused after precipitation in pentane.
19 citations
5 citations
TL;DR: The catalysed enantioselective formation of carbon-nitrogen bonds by the hydroamination reaction is reviewed in this paper. All examples deal with substrates containing non-activated carbon-carbon multiple bonds which are transformed either via intramolecular or intermolecular reactions.
Abstract: The catalysed enantioselective formation of carbon–nitrogen bonds by the hydroamination reaction is reviewed. All examples deal with substrates containing non-activated carbon–carbon multiple bonds which are transformed either via intramolecular or intermolecular reactions. Structurally different complexes already provided nitrogen containing compounds/heterocycles with high enantioselectivities.
2 citations
TL;DR: In this article, a facile method for the preparation of highly active and enantioselective yttrium precatalysts for asymmetric hydroamination of gem-disubstituted aminoalkenes is described.
Abstract: A facile method for the preparation of highly active and enantioselective yttrium precatalysts for asymmetric hydroamination of gem-disubstituted aminoalkenes, from the combination of YCl(3) or YCl(3)(THF)(3.5) with ligand (R)- and n-BuLi is described.