10.1002/anie.200801675
The study provides conclusive evidence for an SN2-Si mechanism in the B(C6F5)3-catalyzed hydrosilylation of carbonyl compounds, which has implications for the related hydrogenation reactions. The researchers used a silane with a stereogenic silicon center as a stereochemical probe to investigate the transition state in the B(C6F5)3-catalyzed hydrosilylation of prochiral acetophenone. They found that the reaction proceeds through a concerted SN2-type displacement at silicon, involving a four-centered cyclic transition state, rather than through a free silylium ion intermediate. This mechanistic understanding is significant for the development of catalytic asymmetric approaches and could guide the design of novel processes in synthetic chemistry. The study also suggests that the efficiency of such reactions may depend on the asymmetric induction of a chiral nonracemic borane catalyst.
10.1002/chem.201103411
The study focuses on the synthesis and investigation of bifunctional azo derivatives that combine push–pull fluorophores and azo photochromes to create fluorescent structures in thin films upon light-induced migration. The researchers systematically explored the photochromic and emissive properties of these bifunctional molecules and compared them to those of corresponding model compounds. They determined fluorescence lifetimes and photoisomerization and fluorescence quantum yields in toluene solution. The study utilized femtosecond transient absorption spectra to reveal that the fluorophores evolve into a distorted intramolecular charge transfer excited state, competing with energy transfer to the azo moiety. A significant finding was the effectiveness of a 10 ? long rigid and nonconjugated bridge between the photoactive units, which inhibits energy transfer and enhances free volume, favoring photoactivated molecular migration in the solid state. The research provides insights into the design of fluorescent photoswitchable molecules for tracking photomechanically-activated single systems and offers new avenues for the development of azo bulk photomigration.
10.1002/ejic.201000802
The study focuses on the synthesis and investigation of ruthenium complexes bearing N-H acidic pyrazole ligands and their application in catalytic hydrogenation reactions. The researchers treated chelate ligands containing pyrazole groups with various ruthenium precursors to form complexes with protic N-H groups near the catalytically active ruthenium center. These complexes were characterized by spectroscopic methods and DFT calculations, and their structure and reactivity were analyzed. The study aimed to understand the role of the acidic N-H groups in metal-ligand-bifunctional hydrogenation, where a hydrido ligand and a proton from a protic group are transferred simultaneously. The catalytic performance of these complexes was evaluated through the hydrogenation and transfer hydrogenation of acetophenone, and the results were connected to the ligand's electronic and structural properties. The research provides insights into the design of efficient catalysts for hydrogenation reactions by leveraging the acidic N-H groups in pyrazole ligands.
10.1016/j.tetlet.2004.09.136
The study focuses on the reactivity of substituted pyridinium N-(20-azinyl)aminides in the Suzuki–Miyaura cross-coupling reaction, a widely used method for forming sp2–sp2 carbon–carbon bonds. The researchers investigated the coupling of these compounds with various boronic acids, using Cs2CO3 as a base, which resulted in good yields and substitution on the negatively charged moiety. They optimized the reaction conditions and found that the process was efficient for a range of substrates, including those with electron-deficient diazine rings, albeit requiring longer reaction times. The study also explored a double Suzuki process with a dibromoaminide to yield diarylated ylides. The results provide a valuable strategy for the synthesis of functionalized 2-aminoazines, which are important in medicinal and heterocyclic chemistry, and the researchers are continuing their efforts to expand the application of this process to other N-aminides.
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.
10.1021/om034385g
The study investigates the reactions of 3-(pentafluorophenyl)indene and (pentafluorophenyl)cyclopentadiene with tetrakis(dimethylamido)titanium(IV), resulting in the formation of products where one or both ortho fluorines of the C6F5 group are replaced by dimethylamino groups. This suggests a titanium-mediated, intramolecular nucleophilic aromatic substitution mechanism. The research led to the isolation of organic products and the conversion of substituted cyclopentadiene to a ferrocene derivative. The study provides insights into the selective activation of polyfluorinated organic compounds, a significant challenge in synthetic chemistry, and contributes to the understanding of transition metal complex mechanisms for C-F activation.
10.1039/b801889h
The study focuses on the activation of the carbon-fluorine (C–F) bond in 1,3-difluoro-2-propanol by the nucleophilic attack of the {Pt2S2} core, a complex with significant nucleophilic properties. The reaction proceeds via an SN2 mechanism, where the sulfur atoms in the [Pt2(dppp)2(μ-S)2] complex act as nucleophiles, facilitated by the hydrogen bond from the alcohol group of the organic substrate, which is crucial for the departure of the fluoride anion. The study demonstrates that the presence of an OH group in the substrate plays a key role in the C–F bond activation, and the reaction leads to the formation of a new complex, [Pt2(dppp)2(μ-S)(μ-SCH2CH(OH)CH2F]F. The research also includes theoretical calculations using DFT methods to support the proposed mechanism and to understand the role of the OH group in the reaction. This work not only contributes to the understanding of C–F bond activation but also provides insights into the role of non-covalent interactions, such as hydrogen bonding, in facilitating chemical transformations.
10.1002/chem.201100160
The research focuses on the doping effect of fluorinated aromatic solvents (FAHs) on the rate of olefin metathesis reactions catalyzed by ruthenium complexes with N-heterocyclic carbene (NHC) ligands. The study explores how the use of FAHs as solvents can significantly enhance the yields of desired products in olefin metathesis reactions, particularly for complex and biologically active molecules. Through a series of experiments, including ring-closing metathesis (RCM), enyne reactions, and cross-metathesis (CM), the researchers observed substantial improvements in turnover numbers (TONs) and yields when using FAHs compared to traditional solvents like 1,2-dichloroethane and toluene. The experiments involved the use of standard commercially available ruthenium pre-catalysts and a variety of substrates to test the efficiency of the reactions under different conditions. Analyses such as X-ray structure analysis, 31P NMR, and computational studies were employed to understand the interactions between the FAHs and the ruthenium catalysts, which were found to improve the efficiency of the olefin metathesis transformation. The study suggests that FAHs can be an attractive alternative medium for promoting challenging olefin metathesis reactions and potentially lead to the design of new improved ruthenium catalysts.
10.1016/S0040-4020(01)00528-2
The study presented in the file involves the synthesis of various compounds through a combination of chemical reactions, such as coupling and cyclization processes, using palladium-catalyzed cross-coupling reactions. Key elements of the study include investigating reaction conditions, optimizing yield, and assessing product purity. The main reactions explored are the coupling of aryl halides with olefins, with different catalysts and solvents. Various aryl halides, olefins, and coupling agents were evaluated to determine their effectiveness in producing specific products, focusing on the yield, reaction time, and stereoselectivity of the final products. The study aims to develop efficient synthetic pathways for producing complex organic molecules.
10.1055/s-0036-1591995
The research focuses on the asymmetric synthesis of cyclopentene-fused tetrahydroquinoline derivatives using N-heterocyclic carbene (NHC) catalyzed domino reactions. The experiments involved a one-pot organocatalytic protocol utilizing readily available quinolinone and enal substrates, with Cs2CO3 as the base and toluene as the solvent. Various NHC precatalysts were screened to optimize reaction conditions, leading to high yields and excellent stereoselectivities. The study analyzed the reaction scope by testing different enals and tetrahydroquinolinone substrates, employing techniques such as HPLC for enantiomeric excess (ee) determination, NMR for product characterization, and X-ray crystallography for confirming the absolute configuration of the synthesized compounds.
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