Refernces
10.1021/ja1084749
The study conducted by Roland Appel, Nicolai Hartmann, and Herbert Mayr from the Department of Chemistry at Ludwig-Maximilians-Universit?t München, investigates the cyclopropanation reactions using sulfur ylides. It focuses on the rates of reactions between stabilized and semistabilized sulfur ylides with benzhydrylium ions and Michael acceptors, measured using UV-vis spectroscopy in DMSO at 20°C. The research establishes a correlation between the second-order rate constants (log k2) and the electrophilicity parameters (E) of the electrophiles, which aids in calculating the nucleophile-specific parameters (N and s) for the sulfur ylides. The findings indicate that the rate constants for cyclopropanation reactions with Michael acceptors align with those for carbocations, suggesting a stepwise mechanism with the initial nucleophilic attack being rate-determining. This study provides a quantitative approach to understanding sulfur ylide reactivity, which is crucial for predicting the scope and limitations of cyclopropanation reactions in organic synthesis.
10.1021/jo8010057
The study focuses on the synthesis and characterization of ethynylhelicene oligomers with perfluorooctyl side chains, ranging from monomers to pentamers. Utilizing circular dichroism (CD) and vapor pressure osmometry (VPO), the research demonstrates the formation of a helix-dimer, particularly in the case of the pentamer within trifluoromethylbenzene at low temperatures and specific concentrations. A comparison between the perfluorooctyl and decyloxycarbonyl side-chained pentamers reveals that the former exhibits lower solubility in organic solvents, forms a more thermodynamically stable helix-dimer, and shows an inverted mirror image CD spectrum. Additionally, the perfluorooctyl pentamer is found to form a hetero-helix dimer with a decyloxycarbonyl pentamer, indicating a higher stability for the hetero-helix dimer over the homo-helix dimers. This work contributes to the understanding of double-helix structures in synthetic oligomers and their potential applications in supramolecular chemistry.
10.1021/ol802336m
The research focuses on the development and application of stable preformed chiral palladium catalysts for the one-pot asymmetric reductive amination of ketones to synthesize chiral amines, which are crucial in pharmaceutical, agrochemical, and materials industries. The study experimented with various carbonyl compounds and aniline derivatives using air-stable preformed complexes such as [(R)-BINAP]PdBr2, [(S)-BINAP]PdBr2, [(R)-Tol-BINAP]PdBr2, and [(S,S)-CHIRAPHOS]PdBr2 as catalysts. The reactions were conducted in chloroform under hydrogen pressure with molecular sieves to absorb water, yielding chiral amines with high enantioselectivities (up to 99% ee). The analyses used to determine the success of the reactions included isolated yields, enantioselectivities determined by HPLC, and in some cases, chiral GC-MS (EI). The study also reported the X-ray structures of two of the catalysts, providing insights into their geometry and potential influence on reactivity and stereocontrol.
10.1016/j.molstruc.2010.10.025
The study focuses on the spectrophotometric determination of formation constants for complexes formed between a newly synthesized Schiff base and transition metal cations (Ni2+, Co2+, Cu2+, Zn2+) in dichloromethane (DCM) and chloroform solutions, using rank annihilation factor analysis (RAFA). The Schiff base, synthesized in the laboratory, served as the ligand for the metal ions. The purpose of these chemicals was to investigate the complexation reactions and determine the stoichiometry and stability constants of the resulting complexes, which have potential applications in various fields such as industrial chemistry, environmental studies, medicinal chemistry, and analytical chemistry. The study aimed to overcome the challenges posed by spectral overlapping in complexation reactions and provide a method for accurately determining stability constants, which are crucial for understanding equilibria in solution.
10.1021/ja00298a040
The research focuses on the synthesis and binding properties of spherands, which are preorganized ligand systems designed to selectively complex with Li+ and Na+ ions. The purpose of this study was to demonstrate the principles of complementarity and preorganization in host-guest chemistry, where the host structures are rigidly organized to specifically accommodate certain guest ions. The conclusions drawn from the research highlight the ability of these spherands to form stable complexes with lithium and sodium ions, while effectively rejecting larger ions such as K+, Ca2+, and Mg2+. This selectivity is attributed to the spherands' preorganized cavities that match the size and electronic properties of Li+ and Na+. The chemicals used in the process include various aryloxy and aryl units, lithium and sodium salts, and solvents like pyridine, chloroform, and benzene, among others, to facilitate the synthesis and complexation reactions. The study also involved the use of 'H NMR spectroscopy to monitor complexation and decomplexation processes, and mass spectrometry to analyze the products.
10.1021/ja01439a015
The study investigates methods for separating lead salts of saturated fatty acids from those of unsaturated fatty acids. The study employs various solvents, including alcohol, chloroform, and ether, to dissolve the lead salts. Chloroform and ether, being more volatile and having greater solvent action, are used to gradually precipitate the more insoluble salts of saturated fatty acids through a fractionation process. The study explores different oils and fats, such as linseed oil, cottonseed oil, olive oil, and mutton tallow, to determine the effectiveness of the separation methods. The results indicate that the fractionation method allows for sharper and more controlled separations, enabling the removal of saturated fatty acid salts with a high degree of purity, especially when the more unsaturated acids like linolenic acid are absent from the oils or fats. The study concludes that the fractionation procedure is a reliable and effective method for separating lead salts of saturated fatty acids from those of unsaturated fatty acids.
10.1021/cm903555s
This study presents the synthesis, physical properties, and self-assembly of a novel type of discotic mesogens based on triphenylene-fused triazatruxenes. These disc-shaped molecules were prepared through microwave-assisted Suzuki coupling reactions and FeCl3-mediated oxidative cyclodehydrogenation. They exhibit extended π-conjugation and possess favorable HOMO energy levels for efficient charge injection from electrodes like gold. The thermal behavior and self-assembly of these mesogens were investigated using techniques such as thermogravimetric analysis, differential scanning calorimetry, polarizing optical microscopy, and variable-temperature X-ray diffraction, revealing good thermal stability and thermotropic liquid crystalline behavior. The charge carrier mobilities of these compounds were determined using the space-charge limited-current (SCLC) technique, with high hole mobilities obtained for TP-TATC6 and TP-TATC12.
10.1039/c5nj02378e
The study presents a novel one-pot method for the catalytic cyclopropanation of various alkenes with unsubstituted hydrazones. The process utilizes iodosobenzene as an oxidant to convert hydrazones into diazo compounds, which are then cyclopropanated in the presence of a nickel(II) catalyst, Ni(OH)2. This method allows for the efficient generation of cyclopropane products under mild conditions (80°C) within a short time frame (5 minutes to 4 hours) and with moderate to good yields (42–91%). The protocol is applicable to a wide range of substrates, including aryl alkenes with different electronic effects, aliphatic alkenes with halogen functional groups, and alkyl acrylates. The study also explores the reaction mechanism and provides a promising approach to synthesizing cyclopropane compounds, which are prevalent in natural products and have significant value in pharmaceutical chemistry.
10.1080/00397910802241407
The research presents the synthesis and characterization of a new series of hydroxy pyrazolines, which are nitrogen-containing heterocyclic compounds known for their broad spectrum of biological activities such as antitumor, immunosuppressive, antibacterial, anti-inflammatory, anticancer, antidiabetic, and antidepressant properties. The study begins with the preparation of 3-phenyl-1-(thiophen-2-yl)prop-2-en-1-one (chalcone 1) through the Claisen-Schmidt condensation of 2-acetyl thiophene with benzaldehyde. This chalcone 1 is then converted into 2,3-dibromo-3-phenyl-1-(thiophen-2-yl)propan-1-one (chalcone dibromide 2) by reacting with bromine in chloroform. Further reaction of chalcone dibromide 2 with various thiosemicarbazides in the presence of triethylamine in absolute ethanol yields hydroxy pyrazolines 3a–h. The synthesized compounds are characterized using IR, 1H NMR, and 13C NMR spectroscopy, with their purity confirmed by elemental analysis. The research also includes the preparation of substituted thiosemicarbazides used in the reaction, and the detailed experimental procedures for the synthesis of each compound are provided in the article.
10.1002/poc.435
The research focuses on the tautomeric preferences of 2-phenylhydrazones of 1,3-diphenyl-1,2,3-trione in chloroform solution, as detected by 15N NMR chemical shifts. The study aims to understand whether the substituent in the phenylhydrazone moiety influences the tautomeric preference and the transmission of the substituent effect within the molecules. Experiments involved the synthesis of compounds through the coupling of benzenediazonium ion to 1,3-diphenyl-1,3-propanedione, followed by purification via recrystallization from ethanol. The synthesized compounds were then analyzed using 1H, 13C, and 15N NMR spectroscopy, with chemical shifts referenced to tetramethylsilane (TMS) and nitromethane. Additionally, ab initio calculations at the HF/B3LYP level of theory with GIAO-HF/DFT method were conducted to calculate the chemical shifts of carbon atoms, and X-ray crystallography was used to detect the tautomer in the crystal state. The study found that the ketohydrazone tautomer is significantly favored over its proton-transfer products, and this tautomer was also detected in the crystalline state, indicating that the additional carbonyl group or substituent does not affect the tautomeric and configurational preferences.
10.1016/j.bmc.2007.10.042
The research focuses on the synthesis and evaluation of novel bis-benzamidino imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydroimidazo[1,2-a]pyridines for their antiprotozoal activity and DNA binding affinity. The key dinitrile intermediates 4a–d were synthesized by reacting phenacyl bromide 1 with appropriate 2-amino-5-bromopyridines to yield 3a–d, followed by Suzuki coupling with 4-cyanophenylboronic acid. The bis-amidoximes 5a–d were then converted to the bis-O-acetoxyamidoximes and further catalytically hydrogenated to yield the acetate salts of 2,6-bis[4-(amidinophenyl)]-imidazo[1,2-a]pyridines 7a–d and the saturated analogue 2,6-bis[4-(amidinophenyl)]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine 8. The N-methoxyamidines 6a–d were prepared as potential prodrugs. These compounds exhibited strong DNA binding affinity and were very active in vitro against Trypanosoma brucei rhodesiense (T. b. r.), with IC50 values between 7 and 38 nM, but less effective against Plasmodium falciparum (P. f.), with IC50 values between 23 and 92 nM. In the T. b. r. STIB900 mouse model, compounds 7c and 7d showed slightly higher activity than furamidine, while only one prodrug 6b exhibited moderate activity. The research highlights the potential of these compounds as antiprotozoal agents and demonstrates the importance of the choice of linker and solvent in the synthesis and activity of these compounds.
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