- Practical methylation procedure for (1H)-1,2,4-triazole
-
Conversion of (1H)-1,2,4-triazole to its sodium salt with methanolic sodium methoxide is followed by reaction with iodomethane. A scalable approach that overcomes problems associated with water-soluble starting material and water-soluble product combined continuous extraction (chloroform/water) with a final short-path distillation under a controlled vacuum to obtain spectroscopically pure 1-methyl-1,2,4-triazole in 63% yield. Adaptation to microwave synthesis conditions, while providing a faster reaction time, offers no product yield or purification advantages over the conventional approach described. Conversions of this product to related derivatives such as 1,4-dimethyl-1,2,4-triazolium iodide and 1-methyl-1,2,4-triazolium hydrochloride are readily achieved. Copyright Taylor & Francis Group, LLC.
- Belletire, John L.,Bills, Robert A.,Shackelford, Scott A.
-
-
Read Online
- Synthesis and Mode of Action Studies on Iridium(I)–NHC Anticancer Drug Candidates
-
We report the synthesis, characterization, and biological activity of IrI complexes with triazole- (NNHC) and thiazole-based (NSHC) N-heterocyclic carbene ligands. Starting from the dimeric [Ir(COD)Cl]2, we obtained complexes of composition Ir(COD)(NNHC)Cl (4a), Ir(COD)(NNHC)X (4b: X = Cl; 4bBr: X = Br), [Ir(COD)(NNHC)(NHC)]I (5a), [Ir(COD)(NSHC)2]Cl (6a), and [Ir(COD)(NSHC)(NNHC)]Cl (6b) by adaptation of established synthetic methods for metal–NHC complexes. Their interactions with model proteins cytochrome c and lysozyme, as well as with the oligonucleotide hexamer (CG)3 (ODN1), were studied. Although most complexes did not show any strong interactions with these biomolecules, all complexes were active against HT-29 and MCF-7 cancerous cells, with IC50 values ranging between 1 and 60 μm. The most active compounds were the cationic bis(carbene) derivatives 5 and 6. All compounds generated high levels of reactive oxygen species (ROS) after incubation for 48 h in MCF-7 cells, possibly suggesting a redox-mediated mechanism of action. Interestingly, there were distinctive differences in the superoxide/(total ROS) ratios induced by the different groups of compounds.
- Gothe, Yvonne,Romero-Canelón, Isolda,Marzo, Tiziano,Sadler, Peter J.,Messori, Luigi,Metzler-Nolte, Nils
-
-
Read Online
- A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki-Heck Reaction
-
Metal complexes bearing N-heterocyclic carbene (NHC) ligands are typically considered the system of choice for homogeneous catalysis with well-defined molecular active species due to their stable metal-ligand framework. A detailed study involving 19 different Pd-NHC complexes with imidazolium, benzimidazolium, and triazolium ligands has been carried out in the present work and revealed a new mode of operation of metal-NHC systems. The catalytic activity of the studied Pd-NHC systems is predominantly determined by the cleavage of the metal-NHC bond, while the catalyst performance is strongly affected by the stabilization of in situ formed metal clusters. In the present study, the formation of Pd nanoparticles was observed from a broad range of metal complexes with NHC ligands under standard Mizoroki-Heck reaction conditions. A mechanistic analysis revealed two different pathways to connect Pd-NHC complexes to "cocktail"-type catalysis: (i) reductive elimination from a Pd(II) intermediate and the release of NHC-containing byproducts and (ii) dissociation of NHC ligands from Pd intermediates. Metal-NHC systems are ubiquitously applied in modern organic synthesis and catalysis, while the new mode of operation revealed in the present study guides catalyst design and opens a variety of novel opportunities. As shown by experimental studies and theoretical calculations, metal clusters and nanoparticles can be readily formed from M-NHC complexes after formation of new M-C or M-H bonds followed by C-NHC or H-NHC coupling. Thus, a combination of a classical molecular mode of operation and a novel cocktail-type mode of operation, described in the present study, may be anticipated as an intrinsic feature of M-NHC catalytic systems.
- Astakhov, Alexander V.,Khazipov, Oleg V.,Chernenko, Andrey Yu.,Pasyukov, Dmitry V.,Kashin, Alexey S.,Gordeev, Evgeniy G.,Khrustalev, Victor N.,Chernyshev, Victor M.,Ananikov, Valentine P.
-
p. 1981 - 1992
(2017/06/14)
-
- Facile Hydrolysis of Nickel(II) Complexes with N-Heterocyclic Carbene Ligands
-
Metal complexes with N-heterocyclic carbene ligands (NHC) are ubiquitously used in catalysis, where the stability of the metal-ligand framework is a key issue. Our study shows that Ni-NHC complexes may undergo facile decomposition due to the presence of water in organic solvents (hydrolysis). The ability to hydrolyze Ni(NHC)2X2 complexes decreases in the order of NHC = 1,2,4-triazolium > benzimidazolium ≈ imidazolium. Depending on the ligand and substituents, the half reaction time of the complex decomposition may change from several minutes to hours. The nature of the halogen is also an important factor, and the ability for decomposition of the studied complexes decreases in the order of Cl > Br > I. NMR and MS monitoring revealed that Ni-NHC complexes in the presence of water undergo hydrolysis with Ni-Ccarbene bond cleavage, affording the corresponding N,N′-dialkylated azolium salts and nickel(II) hydroxide. These findings are of great importance for designing efficient and recyclable catalytic systems, because trace water is a common contaminant in routine synthetic applications.
- Astakhov, Alexander V.,Khazipov, Oleg V.,Degtyareva, Evgeniya S.,Khrustalev, Victor N.,Chernyshev, Victor M.,Ananikov, Valentine P.
-
p. 5759 - 5766
(2016/01/12)
-
- Synthesis and crystal structures of new 1,4-disubstituted 1,2,4-triazoline-5-thiones
-
Introduction of sulfur into the 5-position of 1,4-disubstituted quaternary 1,2,4-triazolium salts (1-9; Cl, Br, I, BF4, PF6, CH3OSO3 were used as anions) by two methods was investigated. The syntheses of nine 1,
- Laus, Gerhard,Kahlenberg, Volker,Wurst, Klaus,Schottenberger, Herwig
-
p. 950 - 964
(2015/06/16)
-
- The catalytic versatility of low toxicity dialkyltriazolium salts: In situ modification facilitates diametrically opposed catalysis modes in one pot
-
The ability of triazolium salts to serve as a precatalyst for both an acid and a powerful base/nucleophile (controlled by additives) has been exploited in a process characterised by a unique in situ catalyst modification strategy. The Royal Society of Chemistry 2013.
- Myles, Lauren,Gathergood, Nicholas,Connon, Stephen J.
-
supporting information
p. 5316 - 5318
(2013/06/27)
-
- Polarity reversal catalysis in radical reductions of halides by N-heterocyclic carbene boranes
-
Otherwise sluggish or completely ineffective radical reductions of alkyl and aryl halides by N-heterocyclic carbene boranes (NHC-boranes) are catalyzed by thiols. Reductions and reductive cyclizations with readily available 1,3-dimethylimidazol-2-ylidene borane and a water-soluble triazole relative are catalyzed by thiophenol and tert-dodecanethiol [C9H 19C(CH3)2SH]. Rate constants for reaction of the phenylthiyl (PhS?) radical with two NHC-boranes have been measured to be ～108 M-1 s-1 by laser flash photolysis experiments. An analysis of the available evidence suggests the operation of polarity reversal catalysis.
- Pan, Xiangcheng,Lacote, Emmanuel,Lalevee, Jacques,Curran, Dennis P.
-
supporting information; experimental part
p. 5669 - 5674
(2012/06/04)
-
- Radical deoxygenation of xanthates and related functional groups with new minimalist N-heterocyclic carbene boranes
-
Minimalist N-heterocyclic carbene boranes 1,3-dimethylimidazol-2- ylideneborane and 2,4-dimethyl-1,2,4-triazol-3-ylideneborane are readily available and have low molecular weights. They exhibit superior performance to first-generation NHC-boranes, providi
- Ueng, Shau-Hua,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max,Curran, Dennis P.
-
supporting information; experimental part
p. 3002 - 3005
(2010/08/20)
-
- Energetic salts of substituted 1,2,4-triazolium and tetrazolium 3,5-dinitro-l,2,4-triazolates
-
Energetic salts comprised of substituted 1,2,4-triazolium and tetrazolium cations and 3,5-dinitro-1,2,4-triazolate anion were synthesized and characterized. The structure of 4,5-dimethyl-1-aminotetrazolium 3,5-dinitro-1,2,4-triazolate (16) was confirmed by X-ray analysis. Based on experimentally obtained heats of combustion, these materials have calculated heats of formation ranging from ΔHf° = 118 (2) to 778 kJ mol-1 (10) with densities >1.5 g cm-3. Salts, 2, 4, 7, 9 and 10, fall into the ionic liquid class (mp 100 °C). The Royal Society of Chemistry 2005.
- Xue, Hong,Twamley, Brendan,Shreeve, Jean'ne M.
-
p. 3459 - 3465
(2007/10/03)
-
- Energetic salts of azotetrazolate, iminobis(5-tetrazolate) and 5, 5′-bis(tetrazolate)
-
Energetic ionic salts of azotetrazolate (AT), iminobis(5-tetrazolate) (IBT) and 5, 5′-bis(tetrazole) (BT) were synthesized; 1-methyl-4- aminotriazolium azotetrazolate has a layered structure and exhibits a heat of formation of 44360 kJ kg-1. The Royal Society of Chemistry 2005.
- Ye, Chengfeng,Xiao, Ji-Chang,Twamley, Brendan,Shreeve, Jean'ne M.
-
p. 2750 - 2752
(2007/10/03)
-
- Catalytic action of azolium salts. VIII. Oxidative aroylation with arenecarbaldehydes catalyzed by 1,3-dimethylbenzimidazolium iodide
-
Refluxing of a mixture of benzaldehyde (1a), 1,3- dimethylbenzimidazolium iodide (7), p-nitroaniline (9b) as an oxidizing agent, and 1,8-diazabicyclo[5,4,0]-7-undecene (DBU) in MeOH afforded methyl benzoate (2a) in good yield. Other methyl arenecarboxylates 2 were similarly obtained from arenecarbaldehydes 1. We showed that this aroylation proceeds via the 2-aroyl-1,3-dimethylbenzimidazolium salt (8). The 1,2,4-triazolium salt (18) and the naphtho[1,2-d]imidazolium salt (19) were also effective catalysts for this oxidative aroylation. However, the aroylation did not proceed with the imidazolium salt (20). In the presence of flavins (25a - c), arenecarbaldehydes 1 reacted in MeOH under aerobic conditions catalyzed by the benzimidozolium salt 7 to give the corresponding methyl arenecarboxylates 2. 1-Methyl-3-[3-(10-phenylisoalloxazin-3-yl)propyl]benzimidazolium bromide (27) is an effective complex catalyst for this oxidative aroylation.
- Miyashita, Akira,Suzuki, Yumiko,Nagasaki, Izuru,Ishiguro, Chie,Iwamoto, Ken-Ichi,Higashino, Takeo
-
p. 1254 - 1258
(2007/10/03)
-
- Azocoupling of Quaternary 1,2,4-Triazolium Salts to Form 5-p-N,N-Dimethylaminophenylazo-1,2,4-triazolium Salts
-
Quaternary 1,2,4-triazolium salts 1 couple easily with p-N,N-dimethylamino-benzenediazonium salts to form azodyes 3 (5-N,N-dimethylaminophenylazo-1,2,4-triazolium salts), preferably under solid-liquid phase transfer conditions using chloroform or methylene chloride and triethylamine or DABCO.Zwitterionic 1,2,4-triazolium salts (anhydro mercapto hydroxide, anhydro hydroxy hydroxide, and anhydro anilido hydroxide ("nitron")) couple as well.The azodyes - as also well known from industrially used types - absorb in the region of 500 nm and have high extinction coefficients.Substituents in 1-, 3- or 4-position of the triazolium ring exert no clear substituent effects.The quaternary 1,2,4-triazolium salts were synthesized according to standard procedures.
- Becker, H. G. O.,Hoffmann, Gerda,Gwan, Kim Mun,Knuepfer, L.
-
p. 325 - 337
(2007/10/02)
-
