Refernces
10.1002/anie.202007030
The study presents a novel light-driven approach to Grubbs metathesis, facilitated by the gem-hydrogenation of internal alkynes using [(NHC)(cymene)RuCl2] (NHC = N-heterocyclic carbene) complexes. This method results in the formation of discrete Grubbs-type ruthenium carbene species, which can be harnessed for a "hydrogenative metathesis" reaction that converts enyne substrates into cyclic alkenes. The research explores the unique reactivity of these complexes under UV irradiation, leading to the efficient formation of various cycloalkene products. The study also discusses the potential and limitations of this new catalyst system, as well as providing experimental evidence for the formation of Grubbs-type carbenes through alkyne gem-hydrogenation. This innovative method offers a non-canonical entry into the field of metathesis chemistry, expanding the scope of catalytic hydrogenation and Grubbs catalysis.
10.1021/ic1020548
The study focuses on the synthesis and characterization of pentacoordinate silicon fluorides featuring amidinate, guanidinate, and triazapentadienate ligands. These compounds were prepared through the fluorination of corresponding chlorosilanes with Me3SnF at ambient temperature. The resulting compounds were characterized using NMR spectroscopy and single-crystal X-ray structural analysis, revealing their molecular structures and confirming the pentacoordinate geometry of the silicon atoms. The study also discusses a one-pot method for preparing base-stabilized silylenes from Si2Cl6, which involves the disproportionation of Si2Cl6 induced by a base, leading to the formation of stable silylenes. This method could be significant for generating and trapping silylene intermediates with various bases, potentially expanding the synthesis of novel silicon compounds. Additionally, the research employed Invariom refinement for a more accurate structural model of one of the compounds, showcasing the application of advanced techniques in structural chemistry.
10.1055/s-0031-1290976
The research focuses on the N-heterocyclic carbene (NHC) catalyzed intramolecular hydroacylation of alkynylphosphonates, leading to the formation of exocyclic and endocyclic olefin tautomers of chromone phosphonates. The study explores the reaction conditions using various NHC catalysts, bases, and solvents to optimize the yields of these tautomers, which are obtained at different temperatures. The experiments utilized reactants such as alkynylphosphonates, NHC catalysts, and potassium carbonate, among others. The analysis of the products involved techniques like thin-layer chromatography (TLC), nuclear magnetic resonance (NMR) spectroscopy (including 1H, 13C, and 31P NMR), mass spectrometry (ESI-MS), and elemental analysis. These methods were employed to characterize the synthesized compounds and confirm their structures, as well as to determine the yields and purities of the products obtained from the reactions.
10.1021/acs.organomet.9b00770
The research focuses on the synthesis and characterization of chiral N-heterocyclic carbene (NHC) iridium complexes, which are investigated for their performance in enantioselective intramolecular hydroamination and ring-opening amination reactions. The study involves the preparation of a series of chiral NHC-iridium complexes with different diene ligands, such as TFB, TCB, BB, and COD. These complexes were synthesized and fully characterized using techniques like X-ray crystallography and NMR spectroscopy. The reactivity and enantioselectivity of these complexes were evaluated in the enantioselective intramolecular hydroamination of N-benzyl-2,2-diphenylpent-4-en-1-amine and the enantioselective ring-opening amination of oxabicycles. The experiments utilized various reactants, including different NHC salts and iridium precursors, and analyses were conducted using 1H and 13C NMR spectroscopy, elemental analysis, and HPLC to determine the yields and enantioselectivities of the reactions. The research also explored the impact of electronic and steric variations on the catalyst platform and identified a highly enantioselective catalyst system for the ring-opening amination of oxabicycles.
10.1002/zaac.201500625
The study investigates the catalytic activity of two palladium(II) complexes, [PdCl(ppy)(IMes)] (4) and [PdCl(ppy){(CN)2IMes}] (6), in the Mizoroki-Heck reaction, a crucial cross-coupling reaction in the synthesis of pharmaceuticals and natural products. These complexes feature different N-heterocyclic carbene (NHC) ligands, IMes and (CN)2IMes, with the latter having a higher π-acceptor strength. The purpose of the study is to evaluate how the π-acceptor strength of the NHC ligands affects the catalytic performance of the complexes. The chemicals used include palladium(II) chloride, 2-phenylpyridine, 1,3-bis(mesityl)imidazol-2-ylidene (IMes), 4,5-dicyano-1,3-bis(mesityl)imidazol-2-ylidene ((CN)2IMes), and aryl halides, which serve as substrates in the Mizoroki-Heck reaction. The study aims to develop more effective precatalysts for this reaction by understanding the influence of the NHC ligands' electronic properties on the reaction's efficiency.
10.1021/om1003607
The research aims to develop a modular synthetic route for a new type of anionic N-heterocyclic carbene (NHC) ligand incorporating an enolate group as a reactive backbone component. This design allows for further tailoring of the ligand's electronic properties even after complexation with transition metals. The study uses key chemicals such as formamidines (Ar-NH-CHdNAr), chloroacetyl chloride, and various electrophiles like pivaloyl chloride, methyl triflate, and triflic anhydride. The researchers also employ transition metals like rhodium and copper in the form of [RhCl(1,5-COD)]2 and CuCl. The purpose is to create NHC ligands with tunable electronic properties through post-functionalization, which can be applied in catalysis. The conclusions show that the electronic properties of the NHC ligands can be effectively modulated over a relatively broad range by adding various electrophiles to the enolate backbone, either at the oxygen or carbon. This provides a versatile method for optimizing catalyst performance in transition metal complex catalyzed reactions.
10.1002/cctc.201800558
This study investigates the synthesis, characterization, and catalytic activity of seven new IrIII complexes containing o-phenoxide or o-naphthoxide chelated N-heterocyclic carbene (NHC) ligands. These complexes efficiently catalyze the transfer hydrogenative reductive amination (RA) of carbonyls and amines in water. The introduction of o-naphthoxide on a nitrogen atom of imidazole-based NHC ligand significantly increases catalytic activity. The study explores the catalytic activity of these complexes in aqueous RA reactions using formic acid/sodium formate as a reducing agent. The mechanism of the reaction is investigated through NMR spectroscopy and kinetic measurements, revealing that the transfer hydrogenation step, specifically the formation of an iridium hydride intermediate, is the turnover-limiting step. The study demonstrates high turnover numbers (TONs) of up to 490 for ketones and 14800 for aldehydes, showcasing the efficiency and versatility of these catalysts in aqueous conditions.
10.1139/cjc-2013-0132
The research explores the utility of palladium complexes supported by morpholine-functionalized N-heterocyclic carbene (NHC) ligands in Buchwald–Hartwig amination. The purpose is to develop new ligands that combine the beneficial features of both SIPr and Mor-DalPhos (MDP) ligands, aiming to achieve high chemoselectivity and activity in palladium-catalyzed cross-coupling reactions. The study synthesizes two new morpholine-substituted NHC ligands, 1-Ar-3-{2-(4-morpholinyl)phenyl}imidazolidin-2-ylidene (Ar = Dipp, Mes), and investigates their coordination behavior and catalytic activity. The key chemicals include the morpholine-functionalized NHC ligands, palladium complexes, and various amines used in the amination reactions. The study finds that while the new ligands can adopt both monodentate and bidentate coordination modes, they perform poorly in Buchwald–Hartwig amination compared to SIPr and MDP ligands. The research concludes that despite the structural similarities, the new ligands do not exhibit the desired catalytic efficiency, suggesting that further modifications or different approaches may be needed to achieve the desired reactivity.
