Showing papers by "Heinz Gornitzka published in 2009"
TL;DR: The anionic imidazol-2-ylidene-4-olate is a salt which can be complexed to a transition metal and still be subsequently functionalized at O or C backbone atom in the outer coordination sphere of the metal.
121 citations
TL;DR: The synthesis of Au(I) and Au(III) complexes, involving alcohol functionalized bis(N-heterocyclic carbene) ligands, and the electrochemical and luminescence properties have been studied.
Abstract: We report the synthesis of Au(I) and Au(III) complexes, involving alcohol functionalized bis(N-heterocyclic carbene) ligands. Two short reaction pathways lead to the diimidazolium precursors, namely 1,1′-(2,6-pyridinediyl)bis[3-(2-hydroxyethyl)-1H-imidazol-3-ium]diiodide (2), 3,3′(methanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]dibromide (4) and 3,3′-(1,3-propanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]bis(4-methylbenzenesulfonate) (6), in which the two azolium rings are bridged by a rigid pyridine unit or an aliphatic chain (C1 or C3). The Au(I) complexes [AuI(Lpy)]22+[PF6−]2 (11) and [AuI(LC1)]22+[PF6−]2 (13) were obtained by direct metallation of the salts 2 and 4, respectively, in the presence of sodium acetate with Au(SMe2)Cl, followed by an anionic metathesis in the presence of KPF6. The trimethylene compound [AuI(LC3)]22+[PF6−]2 (15) was prepared by transmetallation between the related precursor [AgI(LC3)]22+[PF6−]2 (10) and Au(SMe2)Cl. The Au(III) complexes, [AuIII(Lpy)Br2]22+[PF6−]2 (16), [AuIII(LC1)Br2]22+[PF6−]2 (17) and [AuIII(LC3)Br2]22+[PF6−]2 (18) were generated by oxidation of the corresponding Au(I) species with an excess of elemental bromine. Complexes 11, [AuI(LC1)]22+[Br−]2 (12) and 15 have been characterized by single-crystal X-ray diffraction analyses. The electrochemical and luminescence properties of the Au(I) and Au(III) compounds have been studied.
96 citations
TL;DR: The isolation and identification of a new quassinoid named simalikalactone E (SkE), extracted from a widely used Amazonian antimalarial remedy made out of Quassia amara L. (Simaroubaceae) leaves, and its cytotoxicity on mammalian cells was dependent on the cell line, displaying a good selectivity index when tested on nontumorogenic cells.
Abstract: We report the isolation and identification of a new quassinoid named simalikalactone E (SkE), extracted from a widely used Amazonian antimalarial remedy made out of Quassia amara L. (Simaroubaceae) leaves. This new molecule inhibited the growth of Plasmodium falciparum cultured in vitro by 50%, in the concentration range from 24 to 68 nM, independently of the strain sensitivity to chloroquine. We also showed that this compound was able to decrease gametocytemia with a 50% inhibitory concentration sevenfold lower than that of primaquine. SkE was found to be less toxic than simalikalactone D (SkD), another antimalarial quassinoid from Q. amara, and its cytotoxicity on mammalian cells was dependent on the cell line, displaying a good selectivity index when tested on nontumorogenic cells. In vivo, SkE inhibited murine malaria growth of Plasmodium vinckei petteri by 50% at 1 and 0.5 mg/kg of body weight/day, by the oral or intraperitoneal routes, respectively. The contribution of quassinoids as a source of antimalarial molecules needs therefore to be reconsidered.
74 citations
TL;DR: Addition of the germene Mes2Ge=CR2 to 1,4-naphthoquinone yields a singular o-quinodimethane which gives Diels-Alder reactions at room temperature and reacts cleanly with oxygen to form an endoperoxide.
24 citations
TL;DR: In this article, a new substituted 2,3-dichloro-1-λ3σ2-P, 3-λ 3σ3σ3-P-diphosphapropenes Mes*P=C(Cl)-P(Cl)tBu (1) (Mes* = 2,4,6-tri-tert-butylphenyl) and the oxidation compounds Mes*p=C (Cl)-P(=E)(Cl)R [R = tBu, E = S (2), O (
Abstract: New substituted 2,3-dichloro-1-λ3σ2-P,3-λ3σ3-P-diphosphapropenes Mes*P=C(Cl)-P(Cl)tBu (1) (Mes* = 2,4,6-tri-tert-butylphenyl) and the oxidation compounds Mes*P=C(Cl)–P(=E)(Cl)R [R = tBu, E = S (2), O (3); R = Mes, E = O (4)] are reported. From the reaction of 2 with W(CO)5(thf) the chelate compound W(CO)4[Mes*P=C(Cl)–P(S)(Cl)tBu] (5) was obtained. Reaction of 1 or 2 with PdCl2(cod) led to PdCl2[cyMes*PC(H)(Cl)–P(Cl)tBu] (cyMes*P = 5,7-di-tert-butyl-3,3-dimethyl-1-phosphaindane) (6) or PdCl2[cyMes*PC(H)(Cl)–P(S)(Cl)tBu] (7), in which the coordination to the Pd atoms is accompanied by intramolecular addition of CH(tBu) of Mes* to the P=C bond of the dichlorodiphosphapropene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
10 citations