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Stoeckli-Evans, Helen

Nom
Stoeckli-Evans, Helen
Affiliation principale
Email
helen.stoeckli-evans@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/470

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  • Publication
    Métadonnées seulement
    1,4-Bis(hex-yloxy)-2,5-diiodo-benzene
    (2010)
    Thevenet, Damien 
    ;
    Neier, Reinhard 
    ;
    Sereda, Olha
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    The centrosymmetric title compound, C(18)H(28)I(2)O(2), crystallized in the monoclinic space group P2(1)/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosymmetric bromo analogue [Li et al. (2008 (black right triangle)). Acta Cryst. E64, o1930] that crystallized in the triclinic space group P. The difference between the two structures lies in the orientation of the two alkyl chains with respect to the C(aromatic)-O bond. In the title compound, the O-C(alk-yl)-C(alk-yl)-C(alk-yl) torsion angle is 55.8 (5)°, while in the bromo analogue this angle is -179.1 (2)°. In the title compound, the C-atoms of the alkyl chain are almost coplanar [maximum deviation of 0.052 (5) Å] and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue, these two mean planes are almost coplanar, making a dihedral angle of 4.1 (2)°. Another difference between the crystal structures of the two compounds is that in the title compound there are no halide(midline ellipsis)halide inter-actions. Instead, symmetry-related mol-ecules are linked via C-H(midline ellipsis)? contacts, forming a two-dimensional network.
  • Publication
    Métadonnées seulement
    1,4-Bis(hexyloxy)-2,5-diiodobenzene
    (2010)
    Thevenet, Damien 
    ;
    Neier, Reinhard 
    ;
    Sereda, Olha
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    The centrosym. title compd., C18H28I2O2, crystd. in the monoclinic space group P21/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosym. bromo analog that crystd. in the triclinic space group P?1. The difference between the 2 structures lies in the orientation of the 2 alkyl chains with respect to the C(arom.)-O bond. In the title compd., the O-Calkyl-Calkyl-Calkyl torsion angle is 55.8(5)°, while in the bromo analog this angle is -179.1(2)°. In the title compd., the C-atoms of the alkyl chain are almost coplanar [max. deviation of 0.052(5) Å] and this mean plane is inclined to the benzene ring by 50.3(3)°. In the bromo-analog, these 2 mean planes are almost coplanar, making a dihedral angle of 4.1(2)°. Another difference between the crystal structures of the 2 compds. is that in the title compd. there are no halide...halide interactions. Instead, symmetry-related mols. are linked via C-H...? contacts, forming a 2D network. Crystal data: monoclinic, P21/n, a = 9.441(9), b = 7.8455(6), c = 13.457(2) Å, ? = 92.148(12)°, Z = 2, 1216 obsd. reflections with I > 2(I), 101 refined parameters, R[F2 > 2?(F2)] = 0.029, wR(F2) = 0.055. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    The high stereoselectivity of the tandem sequence Diels-Alder reaction/Ireland-Claisen rearrangement starting from substituted O-(E)-buta-1,3-dienyl ketene acetals and cyclic dienophiles
    (2007)
    Soldermann, Nicolas
    ;
    Velker, Joerg
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Neier, Reinhard 
    A new tandem reaction leads to bicyclic cyclohexene derivs., e. g. I, with complete control of the relative configuration of the four chiral centers formed. The high diastereoselectivity is the consequence of an endo-selective Diels-Alder reaction followed by an Ireland-Claisen rearrangement that proceeds via a boat-like transition state. [on SciFinder(R)]
  • Publication
    Accès libre
    The High Stereoselectivity of the Tandem Sequence Diels-Alder Reaction/Ireland­-Claisen Rearrangement Starting from Substituted O-(E)-Buta-1,3-dienyl Ketene Acetals and Cyclic Dienophiles
    (2007)
    Soldermann, Nicolas
    ;
    Velker, Jörg
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Neier, Reinhard 
    A new tandem reaction leads to bicyclic cyclohexene derivatives with complete control of the relative configuration of the four chiral centers formed. The high diastereoselectivity is the consequence of an endo-selective Diels-Alder reaction followed by an Ireland-Claisen rearrangement that proceeds via a boat-like transition state.
  • Publication
    Métadonnées seulement
    Synthesis and characterization of tetrahedral Ru3O clusters with intrinsic framework chirality: a chiral probe of the intact cluster catalysis concept. [Erratum to document cited in CA144:088385]
    (2006)
    Vieille-Petit, Ludovic
    ;
    Süss-Fink, Georg 
    ;
    Therrien, Bruno 
    ;
    Ward, Thomas R.
    ;
    Stoeckli-Evans, Helen 
    ;
    Labat, Gaeel
    ;
    Karmazin-Brelot, Lydia
    ;
    Neels, Antonia
    ;
    Buergi, Thomas
    ;
    Finke, Richard G.
    ;
    Hagen, Collin M.
    On page 6112, Figure 9 was missing and Figure 11 appeared twice. The correct Figure 9 is given. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Synthesis and Characterization of Tetrahedral Ru3O Clusters with Intrinsic Framework Chirality: A Chiral Probe of the Intact Cluster Catalysis Concept
    (2005)
    Vieille-Petit, Ludovic
    ;
    Süss-Fink, Georg 
    ;
    Therrien, Bruno 
    ;
    Ward, Thomas R.
    ;
    Stoeckli-Evans, Helen 
    ;
    Labat, Gaeel
    ;
    Karmazin-Brelot, Lydia
    ;
    Neels, Antonia
    ;
    Buergi, Thomas
    ;
    Finke, Richard G.
    ;
    Hagen, Collin M.
    Triruthenium mixed-ligand tetrahedral oxo-capped clusters with framework chirality were prepd. by redn. of areneruthenium triaqua dications followed by capping with areneruthenium dimer as racemic mixts.; diastereomeric mixts. were prepd. using chiral ligand; the prepd. complexes hydrogenate 2-acetamidoacrylate with no ee. Reaction of ArRuCl(?-Cl)2ClRuAr and Ar1RuCl(?-Cl)2ClRuAr1 with Ag2SO4 in aq. soln. gave mixt. of [ArRu(OH2)3]2+ and [Ar1Ru(OH2)3]2+, which upon NaBH4 redn. afforded mixed-ligand binuclear complex Ar1Ru(?-H)3RuAr (4, Ar = ?6-C6Me6, Ar1 = ?6-cymene). Reaction of 4 with Ar2RuCl(?-Cl)2ClRuAr2 and H2O gave the trinuclear cluster [(ArRu)(Ar1Ru)(Ar2Ru)(?3-O)(?-H)3]+ (rac-5, Ar2 = ?6-C6H6). Diastereomeric complexes [(ArRu)(Ar1Ru)(Ar*Ru)(?3-O)(?-H)3]+ [(S,R)-7, (R,R)-7; Ar* = (R)-1-phenylethanol] were prepd. by reaction of 4 with [Ar*RuCl(?-Cl)2ClRuAr*] (6). Analogous complex [(ArRu)(Ar1Ru)(Ar3Ru)(?3-O)(?-H)3]+ (8) was prepd. as a racemic mixt. from known (S,S)-Ar3RuCl(?-Cl)2ClRuAr3 [Ar3 = Et (R)-N-acetyl-?-aminobenzeneacetate]; the complex 8 was sepd. into diastereomers by chromatog., the racemization being caused by epimerization of the chiral ?-carbon. The enantiopure diastereomeric triruthenium clusters [(ArRu)(Ar1Ru)(Ar4Ru)(?3-O)(?-H)3]+ [(S,S)-17, (R,S)-17; Ar4 = (R)-N-acetyl-?-aminobenzeneethanol isobutyrate] were finally prepd. from (S,S)-Ar4RuCl(?-Cl)2ClRuAr4 and 4. The chiral Ru3O framework was evidenced by x-ray crystallog., by CD in the UV and IR regions, and by chiral shift reagents in the NMR spectra. To bring evidence for or against the hypothesis of catalytic hydrogenation by intact trinuclear arene ruthenium clusters contg. an oxo cap, catalytic hydrogenation of Me 2-acetamidoacrylate catalyzed by complexes 13 was performed; the complexes showed low catalytic activity and no asym. induction. [on SciFinder(R)]
  • Publication
    Accès libre
    The Synthesis of a Pyrazol Analogon of Porphobilinogen with the Help of the Mukaiyama Aldol Reaction
    (2003)
    Chaperon, André
    ;
    Bertschy, Hugo
    ;
    Franz-Schrumpf, Anne-Laurence
    ;
    Hugelet, Bertrand
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Neier, Reinhard 
    The synthesis of a pyrazol analogon of porphobilinogen is described. The Mukaiyama crossed aldol reaction is the key step of our approach. The retrosynthetic analysis follows the mechanism for the biosynthesis of porphobilinogen initially proposed by Shemin.
  • Publication
    Métadonnées seulement
    The synthesis of a pyrazol analogon of porphobilinogen with the help of the Mukaiyama aldol reaction
    (2003)
    Chaperon, André
    ;
    Bertschy, Hugo
    ;
    Franz-schrumpf, Anne-laurence
    ;
    Hugelet, Bertrand
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Neier, Reinhard 
    The synthesis of a pyrazol analogon of porphobilinogen is described. The Mukaiyama crossed aldol reaction is the key step of our approach. The retrosynthetic anal. follows the mechanism for the biosynthesis of porphobilinogen initially proposed by Shemin. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    New iso and heteropolyoxomolybdates: synthesis and molecular structure of the anions [(Mo8O26)-O-VI(OH)](5-), [(HAsAsMoMo8O34)-As-III-Mo-V-Mo-V-O-VI](6-) and [(HAsAsMoMo8O34)-As-III-Mo-V-Mo-V-O-VI{Co(C5H5N)(2)(H2O)(3)}](4-)
    (2002)
    Fidalgo, Eva Garcia
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Süss-Fink, Georg 
    The hydrothermal reaction of Na2MoO4 with pyridine in water at pH 5 and 130 degreesC gives the octamolybdate anion [Mo-8(VI) O-26(OH)](5-) (1) which crystallises as the pyridinium salt; its molecular structure derives from that of the parent alpha-octamolybdate anion [Mo-8(VI) O-26](4-) by opening two molybdenum-oxygen bond and adding a hydroxo bridge. The same reaction in the presence of NaAsO2 yields the mixed-valence arsenatomolybdate [Has(III)As(V)Mo(V)Mo(8)(VI)O(34)](6-) (2) which is also isolated as the pyridinium salt. Anion 2 has a lacunary structure like an open basket, which derives from the famous alpha-Keggin structure by removing three edge-sharing MoO6 octahedra and by capping a trioxygen face of three remaning MoO6 octahedra with an AsH group. Reaction of 2 with Co2+ leads to the anion [(HAsAsMoMo8VI)-As-III-Mo-V-Mo-V O-34 {Co(C5H5N)(2)(H2O)(3)}](4-) (3) which crystallises as a double pyridinium salt together with anion 2. The structure of 3 derives from that of 2 by attaching a Co(C5H5N)(2)(H2O)(3) fragment to a terminal oxo ligand. Reaction of 2 with hydrogen peroxide produces the fully oxydised alpha-Keggin anion [(AsMo12O40)-Mo-V-O-VI](3-) (4) which was found to crystallise as the tetrabutylammonium salt surprisingly with three independent molecules in the unit cell, two of them showing a remarkable disorder. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • Publication
    Métadonnées seulement
    Ru-4(mu-CO)(CO)(9)(eta(4)-mu(4)-C6H4)(eta(2)-mu(1), mu(4)-PPhCH2CH2PPh2): an unusual pyrolysis product of Ru-3(CO)(10)(dppe) containing a benzyne ligand
    (2002)
    Diz, Enrique Lozano
    ;
    Neels, Antonia
    ;
    Stoeckli-Evans, Helen 
    ;
    Süss-Fink, Georg 
    The thermal decomposition of Ru-3(CO)(10)(dppe) in refluxing benzene gives, in contrast to the pyrolysis of the dppm analogue, the tetranuclear cluster Ru-4(mu-CO)(CO)(9)(eta(4)-mu(4)-C6H4) (eta(2)-mu(1), mu(4)-PCH2CH2PPh2) (1) along with Ru-3 (CO)(9)(eta(2)-mu(1), mu(2)-C6H5)(eta(3)-mu(1), mu(2)-PPhCH2CH2PPb2) (2). The single-crystal structure analysis of 1 reveals a square-planar tetraruthenium skeleton containing a eta(4)-mu(4)-benzyne ligand as well as a eta(2)-mu(1), mu(4)-phosphinidene-phosphine ligand. (C) 2002 Elsevier Science B.V. All rights reserved.