Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

Hintermann, Lukas

doi:10.1186/1860-5397-3-22

Cited by 183 publications

(153 citation statements)

References 19 publications

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“…Following literature procedures by Hintermann, [116] 1,4-bis(2,6-diisopropylphenyl)-1,4-diazabutadiene (1) was prepared as a bright yellow crystalline solid. Instead of chloride, acetate was introduced as counterion in the next step by reaction with paraformaldehyde in glacial acetic acid as solvent (Scheme 38).…”

Section: Synthesis Of (Ipr)cuoacmentioning

confidence: 99%

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Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

et al. 2012

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It is better to light a candle than to curse the dark. AbstractThe copper-catalyzed azide-alkyne cycloaddition for the synthesis of 1,4-disubstituted 1,2,3-triazoles (CuAAC) is a variant of Huisgen's 1,3-dipolar cycloaddition which disburdens the thermal reaction from its major drawbacks such as poor regioselectivity, long reaction times and harsh conditions. In contrast to the widely used "black box" reagent mixtures, a molecularly defined, highly active catalyst system for homogeneous CuAAC reactions has been developed in this PhD project. In dependence on the postulated stepwise mechanism, its most important structural feature is the presence of two copper(I) ions irreversibly bound in the same catalyst molecule.A highly modular and profitable synthesis for bistriazolium hexafluorophosphate salts as precursors for the ancillary ligand system was devised. In analogy to the CuAAC catalyst systems of general formula [(NHC) 2 Cu]PF 6 described in literature, novel dinuclear copper(I) complexes with a bistriazolylidene ligand backbone and 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) as sacrificial ligand were prepared.However, these complexes did not show the expected high catalytic activity, most probably due to the strong coordination of the IPr ligands. In consequence, another family of dinuclear copper(I) complexes with m-coordinated acetate as labile ligand was synthesized by reaction of the bistriazolium hexafluorophosphate ligand precursors with copper(I) acetate in the presence of a base.The broad applicability and high catalytic activity of one of these bistriazolylidene dicopper acetate complexes was confirmed by a series of gaschromatographically mo-

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Section: Synthesis Of (Ipr)cuoacmentioning

confidence: 99%

“…procedure reported in literature. [116] In a 500 ml three-necked flask equipped with a thermometer and a dropping funnel, 2,6-diisopropylaniline (92 % pure, ρ = 0.94 g cm 35.57 mmol) were dissolved in glacial acetic acid (130 ml). While the reaction mixture was stirred at 80 °C for three hours, it turned dark purple.…”

Section: Gas Chromatography (Gc)mentioning

confidence: 99%

Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

et al. 2012

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“…2,2=-Bipyridine 3 was obtained from Joachim W. Heinicke, Ernst Moritz Arndt University of Greifswald, Greifswald, Germany. The cytotoxic lipophilic imidazolium salt 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride 3 was synthesized as described previously (54)(55)(56). The arylimidamide DB745 2 (23) was kindly provided by David Boykin, Georgia State University, Atlanta, GA.…”

mentioning

confidence: 99%

In VitroEffects of Novel Ruthenium Complexes in Neospora caninum and Toxoplasma gondii Tachyzoites

Barna

Debache

Vock

et al. 2013

Antimicrob Agents Chemother

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bUpon the screening of 16 antiproliferative compounds against Toxoplasma gondii and Neospora caninum, two hydrolytically stable ruthenium complexes (compounds 16 and 18) exhibited 50% inhibitory concentrations of 18.7 and 41.1 nM (T. gondii) and 6.7 and 11.3 nM (N. caninum). To achieve parasiticidal activity with compound 16, long-term treatment (22 to 27 days at 80 to 160 nM) was required. Transmission electron microscopy demonstrated the rapid impact on and ultrastructural alterations in both parasites. These preliminary findings suggest that the potential of ruthenium-based compounds should thus be further exploited.T oxoplasma gondii and Neospora caninum are cyst-forming apicomplexan parasites that infect a wide range of hosts. In an immunocompetent host, infection with either parasite does not cause disease (1-3). N. caninum has emerged as one of the most important infectious causes of bovine abortion (4-6). In contrast, T. gondii causes toxoplasmosis in humans and many animal species, either in chronically infected individuals during a decrease in immunoreactivity or if a seronegative mother acquires a primary infection during pregnancy, leading to abortion or serious fetal abnormalities (7-9). Toxoplasmosis treatment is based on only a few chemotherapeutics with considerable adverse effects (10, 11). In Neospora-seropositive cattle, pregnancy and the associated immunomodulation are already sufficient to cause recrudescence, fetal damage, and abortion (2-6). Chemotherapy has been considered a promising option if effective drugs can be identified (12, 13). Several compounds were investigated in vitro (14-16), but only a few were evaluated in small-animal models (14,(17)(18)(19)(20)(21)(22)(23)(24).We have evaluated compounds originally synthesized as anticancer drugs. Currently used metal complexes (25-31) exhibit considerable toxicity. This has stimulated the interest in other compounds with more acceptable toxicity, such as ruthenium complexes (32-36). Effects of ruthenium compounds on some bacteria and parasites have been studied (37-46). "Classical ruthenium complexes" contain heteroatom ligands (e.g., azole derivatives), and NAMI-A and KP-1019 have been evaluated in phase I clinical trials for cancer treatment (47-49). Organometallic complexes are defined by at least one metal-carbon bond. The 6 -arene ruthenium(II) phosphite complexes 5, 6, 12, and 15 to 18 were characterized earlier (50), while [Ru( 6 -p-cymene)(bipyridine)Cl][Cl] 11 was synthesized as shown previously (51). Based on our experiences in the design of selective inhibitors of CYP11B2 (53) and CYP11B1 (54), the pyridine-based compounds 4, 7 to 10, and 14 were from a small in-house library of CYP enzyme inhibitors. 2,2=-Bipyridine 3 was obtained from Joachim W. Heinicke, Ernst Moritz Arndt University of Greifswald, Greifswald, Germany. The cytotoxic lipophilic imidazolium salt 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride 3 was synthesized as described previously (54-56). The arylimidamide DB745 2 (23) was kindly provided by David Bo...

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“…However, the cyclization of the sterically demanding diimines to the respective azolium salts turned out to be difficult as the standard procedure [2b] did not lead to the formation of the desired products. Next, the Hintermann synthesis [14] was tested for the cyclization reaction of diimine 4a. The desired azolium salt was ob-tained in approximately 25 % yield, but turned out to be highly impure and could not be purified.…”

Section: Synthesis Of New Nhc Ligandsmentioning

confidence: 99%

Metal Complexes of Very Bulky N,N′‐Diarylimidazolylidene N‐Heterocyclic Carbene (NHC) Ligands with 2,4,6‐Cycloalkyl Substituents

Savka

Plenio

2014

Eur J Inorg Chem

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Abstract1,3,5‐Tricycloalkylbenzene (cycloalkyl = C5H9, C6H11) was converted into the respective anilines (by means of nitration and reduction) and then into the corresponding diimines (with glyoxal), the cyclization of which with (HCHO)n/ZnCl2 provided the respective 1,3‐bis(2,4,6‐tricyclopentylphenyl)imidazolium salt in modest yields. An analogous reaction sequence that employed acenaphthene‐1,2‐dione instead of glyoxal yielded the two azolium salts in good yields, which were converted into the respective N‐heterocyclic carbene (NHC) complexes [(NHC)AgCl], [(NHC)AuCl], [(NHC)RhCl(cod)] (cod = cyclooctadiene), and [(NHC)RhCl(CO)2].

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Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

Cited by 183 publications

References 19 publications

Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

Highly Active Dinuclear Copper Catalysts for Homogeneous Azide–Alkyne Cycloadditions

In VitroEffects of Novel Ruthenium Complexes in Neospora caninum and Toxoplasma gondii Tachyzoites

Metal Complexes of Very Bulky N,N′‐Diarylimidazolylidene N‐Heterocyclic Carbene (NHC) Ligands with 2,4,6‐Cycloalkyl Substituents

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