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Université de Neuchâtel

Catalytic Hydrogenation of meso-Octamethylporphyrinogen (Calix[4]pyrrole)

Journot, Guillaume ; Letondor, Christophe ; Neier, Reinhard ; Stoeckli-Evans, Helen ; Savoia, Diego ; Gualandi, Andrea

In: Chemistry - A European Journal, 2010, vol. 16, no. 4, p. 4224-4230

Hydrogenation of meso-octamethylporphyrinogen (calix[4]pyrrole) with a number of heterogeneous catalysts under different experimental conditions has been investigated. GC-MS analyses of the reaction mixtures showed the formation of one to four products in low to moderate yields: three of them were diastereoisomers of the product derived from half-hydrogenation of the substrate, and displayed...

Université de Neuchâtel

5-Hydroxyalkyl derivatives of tert-butyl 2-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate: diastereoselectivity of the Mukaiyama crossed-aldol-type reaction

Vallat, Oliver ; Buciumas, Ana-Maria ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Acta Crystallographica Section C : Crystal Structure Communications, 2009, vol. C65, no. 4, p. o171-o175

The title compounds, rac-(1'R,2R)-tert-butyl 2-(1'-hydroxyethyl)-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate, C17H20N2O6, (I), rac-(1'S,2R)- tert-butyl 2-[1'-hydroxy-3'-(methoxycarbonyl)propyl]-3-(2-nitrophenyl)-5-oxo-2,5-dihydro-1H-pyrrole-1-carboxylate,...

Université de Neuchâtel

4,4-Bis(1H-pyrrol-2-yl)pentanol

Journot, Guillaume ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Acta Crystallographica Section E : Structure Reports Online, 2010, vol. E66, no. 2, p. o393, sup1-8

The title achiral compound, C13H18N2O, crystallized in the chiral monoclinic space group P21. The pyrrole rings are inclined to one another by 62.30 (11)°, and the propanol chain is in an extended conformation. In the crystal, the two pyrrole NH groups are involved in intermolecular N-H ··· O hydrogen bonds, leading to the formation of a...

Université de Neuchâtel

Rac-(2R*,3R*)-S-Ethyl-4-Chloro-3-Hydroxy-2-Phenylbuthanethioate and Rac-(2R*,3R*)-S-Ethyl-2-Phenyl-3-(tosyloxy)buthanethioate: Dichotomy of the Stereoselectivity of the Mukaiyama Reaction

Vallat, Oliver ; Buciumas, Ana-Maria ; Neier, Reinhard ; Stoeckli-Evans, Helen

In: Journal of Chemical Crystallography, 2009, vol. 40, no. 1, p. 10-14

The title compounds, rac-(2R*,3R*)-S-ethyl-4-chloro-3-hydroxy-2-phenylbuthanethioate (I) and rac-(2R*,3R*)-S-ethyl-2-phenyl-3-(tosyloxy)buthanethioate (III), are both composed of a S-ethyl 2-phenylbutanethioate moiety but have different geometries. Compound I is substituted in the 3 and 4 positions by a hydroxyl group and a chlorine atom, respectively. In compound III...

Université de Fribourg

Stereoselective synthesis of cyclometalated iridium(III) complexes: characterization and photophysical properties

Yang, Liangru ; Zelewsky, Alexander von ; Nguyen, Huong P. ; Muller, Gilles ; Labat, Gaël Charles ; Stoeckli-Evans, Helen

In: Inorganica Chimica Acta, 2009, vol. 36, no. 10, p. 3853-3856

The stereoselective synthesis of a highly luminescent neutral Ir(III) complex comprising two bidentate chiral, cyclometalating phenylpyridine derivatives, and one acetylacetonate as ligands is described. The final complex and some intermediates were characterized by X-ray structural analysis, NMR-, CD-, and CPL-spectroscopy.

Université de Neuchâtel

Protonation and Zn(II) complexation with versatile valine and glycylglycine N-pyrimidines derivatives: crystal structures of layered {[Zn(HL1)2] • 2H2O}n and [Zn(HL2)2 (H2O)4]

López-Garzón, R. ; Godino-Salido M. L. ; Arranz-Mascarós, P. ; Fontecha-Cámara, M.A. ; Gutiérrez-Valero, M. D. ; Cuesta, R. ; Moreno, J.M. ; Stoeckli-Evans, Helen

In: Inorganica Chimica Acta, 2004, vol. 357, no. 7, p. 2004

Protonation and Zn(II) complexation of N-substituted amino acids, valine (H2L1) and glycylglycine (H2L2), with 4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidin-2-yl as substituent, were studied by potentiometric and UV–Vis measurements. Bianions L1 and L2 suffer three protonation steps in aqueous medium corresponding to the amide and carboxylate groups of the...

Université de Neuchâtel

Synthesis and structural analysis of palladium biscarbene complexes derived from bisimidazolium ligand precursors

Heckenroth, Marion ; Neels, Antonia ; Stoeckli-Evans, Helen ; Albrecht, Martin

In: Inorganica Chimica Acta, 2006, vol. 359, no. 6, p. 316-330

The palladation of potentially chelating bisimidazolium ligand precursors with palladium acetate gives bridging bimetallic, chelating monometallic, and homoleptic tetracarbene complexes. The coordination mode of the biscarbene ligand has been identified by spectroscopic analysis and crystallographic characterization of representative complexes, including the first example of a biscarbene A-frame...

Université de Neuchâtel

Oxidation of alkanes with m-chloroperbenzoic acid catalyzed by iron(III) chloride and a polydentate amine

Shul’pin, Georgiy B. ; Stoeckli-Evans, Helen ; Mandelli, Dalmo ; Kozlov, Yuriy N. ; Tesouro Vallina, Ana ; Woitiski, Camile B. ; Jimenez, Ricardo S. ; Carvalho, Wagner A.

In: Journal of Molecular Catalysis A: Chemical, 2004, vol. 219, no. 25, p. 255-264

Tetradentate amine N,N′-bis(2-pyridylmethylene)-1,4-diaminodiphenyl ether (compound 1) dramatically accelerates the oxidation of alkanes with MCPBA in acetonitrile catalyzed by FeCl3, whereas N,N′-bis(2-pyrrolidinmethylene)-1,4-diaminodiphenyl ether (2) does not affect the reaction. The selectivity of the reaction in the presence of 1 is...

Université de Neuchâtel

Study of protonation and Zn(II), Cd(II), Cu(II) and Mn(II) complexation with a glutamic acid N-pyrimidine derivative: Crystal structure of a neutral Cd(II) complex of the bianionic ligand

Arranz-Mascarós, P. ; Gutiérrez-Valero, M. D. ; López-Garzón, R. ; López-León, M. D. ; Godino-Salido M. L. ; Santiago-Medina, A. ; Stoeckli-Evans, Helen

In: Polyhedron, 2008, vol. 27, no. 2, p. 623-632

The compound N-(4-amino-1-methyl-5-nitroso-6-oxo-1,6-dihydropyrimidin-2-yl)-(s)-glutamic acid (H3L) was synthesised and structurally characterised by analytical methods and 1H, 13C and 15N NMR spectroscopy. This compound (H3L) shows the same topology as other model receptors previously used to develop chemical functionalization at the...

Université de Neuchâtel

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

Soldermann, Nicolas ; Velker, Jörg ; Neels, Antonia ; Stoeckli-Evans, Helen ; Neier, Reinhard

In: Synthesis, 2007, vol. 15, p. 2379-2387

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.