36339-13-6Relevant academic research and scientific papers
Quinoidal tetrazines: Formation of a fascinating compound class
Bostai, Beatrix,Novaky, Zoltan,Benyei, Attila C.,Kotschy, Andras
, p. 3437 - 3439 (2007)
A series of different N-heterocyclic carbenes (NHCs) were reacted with 3,6-bis(3′,5′-dimethylpyrazolyl)-tetrazine in the presence of an inorganic carbonate to provide access to a hitherto unprecedented compound class. The formed tetrazine derivatives bearing the NHC in the 3-position and an oxygen in the 6-position show a quinoidal-like structure, according to physical examinations and X-ray crystallography.
Benzimidazolium salts as starting materials or intermediates in 1,3-dipolar cycloadditions
Macsim, Ana-Maria,Georgescu, Emilian,Georgescu, Florentina,Filip, Petru,Nicolescu, Alina,Deleanu, Calin
, p. 845 - 852 (2021/07/17)
Several new benzimidazolium salts have been synthesized and fully characterized by multinuclear NMR spectroscopy. The benzimidazolium salts occur as intermediates in various 1,3-dipolar cycloadditions and they are also useful as starting materials in such cycloadditions. Graphic abstract: [Figure not available: see fulltext.].
Mechanism studies of oxidation and hydrolysis of Cu(I)–NHC and Ag–NHC in solution under air
Li, Dazhi,Ollevier, Thierry
supporting information, (2019/11/29)
The decomposition of copper(I)–NHC and silver-NHC complexes in solution under air was studied. The Cu(I)–NHCs were oxidized into urea derivatives and hydrolysed into imidazoliums or benzimidazoliums. The decomposition of Ag–NHC with a saturated backbone led to ring-opening product, while the Ag–NHC with an unsaturated backbone led to imidazolium and Ag-bisNHC complex. The effects of steric property, hydrophilicity, and binding energy of NHC to O2 and H2O on the decomposition of Cu(I)–NHC were studied using theoretical calculations. Steric hindrance played an important role on the stability of Cu(I)–NHC. Pathways for the decomposition of Cu(I)–NHC and Ag–NHC were proposed.
Synthesis of Imidazolidinone, Imidazolone, and Benzimidazolone Derivatives through Oxidation Using Copper and Air
Li, Dazhi,Ollevier, Thierry
supporting information, p. 3572 - 3575 (2019/05/24)
A new synthetic method of urea derivatives using copper and air was developed. These mild conditions provided moderate to very good yields for 15 examples (53-93%), while low yields were obtained with sterically hindered substrates (3 examples). The reaction was found to go through an in situ generated copper-N-heterocyclic carbene, which was then oxidized into cyclic urea derivatives possessing alkyl, benzyl, aryl, hydroxy, Boc-protected, and tertiary amine groups.
Robust, Highly Luminescent Au13 Superatoms Protected by N-Heterocyclic Carbenes
Narouz, Mina R.,Takano, Shinjiro,Lummis, Paul A.,Levchenko, Tetyana I.,Nazemi, Ali,Kaappa, Sami,Malola, Sami,Yousefalizadeh, Goonay,Calhoun, Larry A.,Stamplecoskie, Kevin G.,H?kkinen, Hannu,Tsukuda, Tatsuya,Crudden, Cathleen M.
supporting information, p. 14997 - 15002 (2019/11/02)
Gold superatom nanoclusters stabilized entirely by N-heterocyclic carbenes (NHCs) and halides are reported. The reduction of well-defined NHC-Au-Cl complexes produces clusters comprised of an icosahedral Au13 core surrounded by a symmetrical arrangement of nine NHCs and three chlorides. X-ray crystallography shows that the clusters are characterized by multiple CH-πand π-πinteractions, which rigidify the ligand and likely contribute to the exceptionally high photoluminescent quantum yields observed, up to 16.0%, which is significantly greater than that of the most luminescent ligand-protected Au13 superatom cluster. Density functional theory analysis suggests that clusters are 8-electron superatoms with a wide HOMO-LUMO energy gap of 2 eV. Consistent with this, the clusters have high stability relative to phosphine stabilized clusters.
Cu–N-heterocyclic carbene-catalysed synthesis of 2-aryl-3-(arylethynyl)quinoxalines from one-pot tandem coupling of o-phenylenediamines and terminal alkynes
Motakatla, Venkata Krishna Reddy,Gokanapalli, Anusha,Peddiahgari, Vasu Govardhana Reddy
, (2019/09/03)
A series of new benzimidazolium chlorides bearing N,N′-benzyl, 2,4,6-trimethylbenzyl and 2,4,6-triisopropylbenzyl substituents have been designed and synthesized from various o-phenylenediamines. Subsequently, corresponding Cu-based N-heterocyclic carbenes (NHCs) were generated in situ in the reaction medium which represents a new application of NHCs exploiting distinct catalytic property towards intermolecular cyclization reaction cascade for the synthesis of 2-aryl-3-(arylethynyl)quinoxalines from o-phenylenediamines and terminal alkynes. The outcome of the cyclization reaction product depends upon the N,N′-substituents present on the benzimidazolium chlorides.
Catalytic synthesis method of 2-pyridone
-
Paragraph 0034-0035, (2018/05/30)
The invention relates to a catalytic synthesis method of 2-pyridone. A 5-acyl-3,4-dihydropyran compound, a substituted acetonitrile compound, a catalyst HCP-NHC-Cu and a solvent are mixed for reacting. The molar ratio of the 5-acyl-3,4-dihydropyran compound to the substituted acetonitrile compound is 1:(1.05 to 1.2); the molar ratio of the 5-acyl-3,4-dihydropyran compound to the catalyst HCP-NHC-Cu is 1:(0.01 to 0.1); the catalyst HCP-NHC-Cu is carbene-based micropore organic polymer-supported CuCl; the reaction temperature is 80 to 120 DEG C, and the reaction time is 6.0 to 10.0 hours. Afterthe reaction is finished, the 2-pyridone is obtained after filtration and column chromatography. The synthesis method provided by the invention has the advantages of mild reaction condition, simple process, high yield and environment friendliness.
A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki-Heck Reaction
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)
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.
Highly efficient carbene and polycarbene catalysis of the transesterification reaction
Marichev, Konstantin A.,Korotkikh, Nikolai I.,Cowley, Alan H.,Saberov, Vagiz Sh,Glinyanaya, Nataliya V.,Rayenko, Gennady F.,Shvaika, Oles P.
, p. 365 - 376 (2018/05/07)
Highly efficient carbene and polycarbene catalysis of the transesterification reaction of ethyl benzoate in methanol has been observed and results in values of TON as high as 4000–6150 at a molar ratio of ester to methanol of 1:18 at room temperature. The most effective catalysts were found to be the individual carbenes or in situ generated carbenes, namely adamantyl and aromatic substituted cyclic compounds and polymeric carbenes. None of the reactions requires the use of molecular sieves. The polymeric imidazol-2-ylidene catalyst was used for the efficient production of biodiesel fuel from sunflower oil.
N-heterocyclic carbene-catalyzed α-alkylation of ketones with primary alcohols
Zhu, Yanfang,Cai, Chun,Lu, Guoping
, p. 1666 - 1671 (2015/01/09)
Several N-heterocyclic carbene precursors are synthesized and used in the α-alkylations of ketones with primary alcohols. With the assistance of a base, these N-heterocyclic carbenes can catalyze the reaction smoothly to furnish dialkylated ketones in good-to-excellent yields.
