10.1002/chem.201002076
The study presents the development of a series of eight new [2]rotaxane molecules, with a focus on the first sulfonamide interlocked system, designed to selectively recognize chloride anions in aqueous media. The research leverages a chloride-anion-templating synthetic pathway to create these [2]rotaxanes, whose three-dimensional interlocked-binding domains exhibit high chloride selectivity. The study utilizes 1H NMR spectroscopic titration to demonstrate the rotaxanes' chloride recognition capabilities and employs X-ray structural analysis and computational molecular dynamics simulations to elucidate the formation yields, anion binding affinities, and selectivity trends. The findings reveal that the rotaxanes can selectively bind chloride even in competitive aqueous solvent mixtures, with the binding affinity tunable through modifications such as electron-withdrawing substituents and charge increase. The research contributes to the advancement of anion recognition in supramolecular chemistry and has implications for nanotechnological applications.
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.tet.2008.03.027
The study presents an investigation into the selective synthesis of functionalized cycloheptadienes through tandem enyne metathesis, utilizing Grubbs' catalyst to achieve regio- and site-selective ring expansion of dienes and substituted cyclopentenes. The research focuses on the influence of ring strain on the reactivity and selectivity of the metathesis process, elucidating the mechanistic aspects that contribute to the formation of 1,3-cycloheptadienes. The study also explores the reaction's scope and limitations, including the impact of different substituents and the potential for further functionalization of the synthesized cycloheptadienes. The findings provide valuable insights into the control of alkene stereoselectivity in enyne metathesis and the development of efficient synthetic strategies for complex molecule synthesis.
10.1039/c0cc02986f
The study presents the synthesis and characterization of novel, highly colored benzopentalenonaphthalenones derived from the intramolecular capture of a merocyanine moiety from diarylmethanol-substituted 2H-naphtho[1,2-b]pyrans under acidic conditions. These compounds exhibit interesting photochromic properties, changing color upon irradiation with ultraviolet light and reverting to colorless upon cessation of irradiation. The researchers also observed that the coloration was influenced by the electronic and steric properties of the substituents. Further, they explored the cascade process that leads to the formation of these compounds, involving initial intramolecular trapping of a cation and subsequent cyclization, tautomerization, and oxidation steps. The study provides insights into the design of new functional dyes with potential applications in areas such as dye-sensitized solar cells, photodynamic therapy, and sensor systems.
10.1055/s-0031-1291135
The study focuses on the copper-catalyzed 1,3-dipolar cycloaddition of (arylselanyl)alkynes with benzyl azides, producing a series of novel [(arylselanyl)alkyl]-1,2,3-triazoles. This reaction, known as click chemistry, was performed under mild conditions using copper(II) acetate monohydrate and sodium ascorbate as catalysts. Various substituted benzyl azides, both electron-withdrawing and electron-donating, were reacted with different (arylselanyl)alkynes, yielding high amounts of selenium-containing triazoles. The synthesized compounds show potential for biological applications, expanding the utility of selenium-containing heterocycles in organic chemistry.
10.1021/jo402853v
The research focuses on the enantioselective desymmetrization of prochiral diesters to produce lactones with high enantiomeric purity, utilizing a chiral phosphoric acid catalyst. The study is significant for its potential in asymmetric synthesis, particularly for creating biologically active molecules with all-carbon quaternary centers. The experiments involved the preparation of various prochiral diesters through alkylation of di-tert-butyl malonate with different alkyl halides and subsequent reactions to form hydroxy diesters. These diesters were then subjected to desymmetrization using the chiral catalyst in dichloromethane, yielding lactones with high yields and enantioselectivity. The scalability of the process was demonstrated, and the utility of the lactone products was showcased through their conversion into functionalized building blocks. Analyses included NMR for structural confirmation, IR for functional group identification, HRMS for molecular weight determination, and GC and HPLC for assessing enantiomeric excess, providing comprehensive characterization of the synthesized compounds.
10.1016/j.jorganchem.2011.12.014
The research focuses on the synthesis and characterization of novel platinum(II) complexes with pyrimidine-functionalized N-heterocyclic carbene (NHC) ligands, aiming to merge successful systems for the activation and functionalization of methane. The study involves the preparation of platinum(II) complexes with aryl and alkyl substituents through transmetalation using corresponding silver complexes. The reactants include imidazolium salts, Ag2O, and [(COD)PtCl2], with the synthesis carried out in dichloromethane or DMSO under specific conditions. The characterization of the complexes was performed using 1H and 13C-NMR spectroscopy, elemental analysis, and X-ray single crystal structures for five compounds. The complexes were tested for catalytic activity in methane activation but showed no significant catalytic activity under the tested conditions. The detailed analyses include melting points determination, NMR spectroscopy, and X-ray crystallography, with results indicating stable complexes under strong acidic conditions but without catalytic activity in methane oxidation.
10.1021/ol006146k
The research focuses on the asymmetric Wolff rearrangement reactions using α-amino-α'-methyl-α'-diazoketones to synthesize α-methyl-β-amino acid esters with good stereoselectivity. The study examines factors influencing the stereochemistry, such as steric effects and temperature dependence. The reactants include α-alkylated-α-diazoketones prepared from α-amino acids through a two-step process involving diazomethane coupling and anionic alkylation reactions. The Wolff rearrangement reactions are initiated using UV light at -78 °C in dichloromethane to generate intermediate ketenes, which are then trapped with nucleophiles like alcohols to yield α-methyl-β-amino acid derivatives. The stereochemistry of the major diastereoisomer was determined to be anti through single-crystal X-ray crystallographic analysis and chemical correlations. The experiments also revealed that the steric size of substituents and the nitrogen protecting group significantly affected the diastereomeric ratios, with Boc protecting group showing higher stereoselectivity than Fmoc. Temperature was found to be a crucial factor, with better diastereoselectivity at lower temperatures. The analysis included 1H NMR, HPLC, and X-ray crystallography to determine the ratios and stereochemistry of the products.
10.14233/ajchem.2014.16893
The research primarily focuses on the synthesis, characterization, and in vitro antitumor activity evaluation of novel Schiff base compounds containing a pyrazole group. The synthesis involved the condensation reaction of 1-arylpyrazol-4-carbaldehyde with benzene hydrazine or phenylhydrazine hydrochloride, using methanol as a solvent and refluxing at 80°C for 2 hours. The reaction was optimized to avoid the use of additional catalysts to prevent complex post-processing. The synthesized compounds were purified through crystallization using a mixture of ethanol and dichloromethane. Characterization of the compounds was achieved using nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, mass spectrometry (MS), and elemental analysis. The in vitro antitumor activity was assessed by testing the compounds B2 and B4 against the K562 human leukemia cell line using the MTT assay method, with aminonide as a reference substance. The study found that these compounds exhibited antiproliferative activity against K562 cells, inhibiting their growth.
10.1021/jo0015974
The research focuses on the synthesis of R-keto esters and amides, which are crucial functional groups for inhibitors of hydrolytic enzymes such as serine and cysteine proteases. The study extends the method of oxidative cleavage of cyanoketophosphoranes using dimethyldioxirane as a mild and selective oxidant, followed by trapping with nucleophiles to yield the desired R-keto compounds. The experiments involved the preparation of cyanoketophosphoranes by coupling corresponding carboxylic acids with (cyanomethylene)phosphorane in the presence of EDCI. The oxidative cleavage was performed by adding dimethyldioxirane to solutions of cyanoketophosphoranes in MeOH for esters or in CH2Cl2 at -78 °C for amides, followed by the addition of the appropriate amine or alcohol nucleophile. The analyses used to characterize the products included flash column chromatography, analytical TLC, NMR spectroscopy (1H and 13C), infrared spectroscopy (IR), electron impact mass spectrometry (EIMS), and high-resolution mass spectrometry (HRMS). The study successfully demonstrated a mild and efficient method for synthesizing R-keto esters and amides with short reaction times and simple workup procedures.
10.1002/adsc.200700333
The research focuses on the copper-catalyzed multicomponent reactions (MCRs) of terminal alkynes, acid chlorides, and carbodiimides to synthesize functionalized propiolamidine derivatives. The study explores the efficiency of various bases and solvents to optimize the reaction conditions. The optimal catalytic system was found to be a combination of CuI, triethylamine (TEA), and acetonitrile (CH3CN), yielding the desired products in good to excellent yields. The experiments involved a suspension of carbodiimide and acid chloride, followed by the addition of anhydrous acetonitrile, TEA, CuI, and alkyne at room temperature under a nitrogen atmosphere. The reaction mixture was stirred, then extracted with CH2Cl2, washed with saturated NaHCO3 solution and water, dried over anhydrous MgSO4, and evaporated under vacuum. The residue was purified using silica gel column chromatography with petroleum ether/ethyl acetate as the eluent. The analysis of the reaction products was based on isolated yields, which were calculated based on the amount of N,N’-dialkylcarbodiimides used.
10.1080/00397910802419680
The research focuses on the efficient synthesis of 7-amino-3-hydroxyindan-1-one, a three-dimensional, three-point scaffold with potential applications in constructing focused compound libraries for biological interactions. The synthesis is achieved through a three-step process: first, reacting 4-nitrophthalic anhydride with ethyl acetoacetate, acetic anhydride, and triethylamine in methylene chloride to produce compound 10; second, hydrolyzing and decarboxylating compound 10 with trifluoroacetic acid in acetonitrile to yield 4-nitroindan-1,3-dione (11); and third, reducing compound 11 using catalytic hydrogenation with 10% Pd/C in methanol to obtain the final product, 7-amino-3-hydroxyindan-1-one (7). The structure of compound 7 was confirmed using heteronuclear multiple bond correlation (HMBC) spectral studies. The article also details the preparation of N-substituted derivatives of compound 7 and provides their physical constants, spectral data, and yields. Analytical techniques used include NMR spectroscopy, LC/MS, and melting point determination, ensuring the purity and structure of the synthesized compounds.
10.1002/anie.200500689
The research focuses on the synthesis and modification of heteroligated monometallic RhI tweezer-type complexes, aiming to develop functional metallosupramolecular entities with preprogrammed catalytic and molecular-sensing properties. The study introduces a high-yielding methodology for preparing these complexes using hemilabile ligands like Ph2P(CH2)2SAr and Ph2P(CH2)2XC6H5 (X = O, CH2), along with [{RhCl(nbd)}2] in CH2Cl2. The researchers discovered that the reaction rates of the ligand rearrangement to form semiopen complexes 3a–f are inversely proportional to the electron density of the aryl groups. They also demonstrated the reversible abstraction of Cl- ions and the subsequent formation of various geometries through reactions with NaBArF and CO. The study concludes that this synthetic approach allows for the systematic control of spatial separation and flexibility between the aryl groups, enabling the design of catalytic intramolecular systems with precise control over these properties, which is significant for the development of allosteric catalysts and sensors.
10.1016/0022-328X(83)80229-0
The research explores the potential of a "mono-P-donor crown ether" hybrid ligand, specifically derivatives of 1,10-dioxa-4,7-diaza-11-phosphacycloundecane, to activate coordinated carbon monoxide (CO) via selective cation binding. The purpose is to enhance nucleophilic addition to coordinated CO in metal carbonyl complexes by stabilizing acylate/benzoylate products through selective cation binding effects. Dichloromethane was used as a solvent for storing the complexes 6. It helps in maintaining the stability of the complexes under low-temperature conditions (-20°C). The study demonstrates that these ligands can stabilize benzoylate/acylate products by selectively binding Li+ ions, as shown in the formation of lithium benzoylate/acylate complexes (complexes 6). The structure of one such product was determined by X-ray crystallography, revealing a dimeric arrangement with a distorted tetrahedral environment around the Li+ ion. The research concludes that while these mono-P-donor crown ether systems can stabilize benzoylate/acylate intermediates, the presence of N-donor functions in the ligand may not be ideal for catalytic systems due to their coordination to the metal carbonyl center. Efforts are ongoing to design "all oxygen" mono-P-donor crown ether systems to overcome this limitation.
10.1021/acs.organomet.7b00603
The study investigates the impact of ligands on the reactivity of iron complexes in the reductive radical cyclization of unsaturated organic halides. It focuses on the role of ligands in the structure and reactivity of active anionic iron(I) hydride and borohydride species. The researchers synthesized an iron(II) borohydride complex, [(η1-H3BH)FeCl(NCCH3)4], and compared its catalytic properties with those of the iron(II) hydride complex, [HFeCl(dppe)2]. The study found that the ligand environment significantly influences the catalyst's ability to activate substrates, with the borohydride complex being more effective in activating both iodo- and bromoacetals compared to the hydride complex. The research provides new insights into the design of radical mediators, emphasizing the importance of ligand tailoring on the metal center for successful catalysis.
10.1021/ja00212a030
The study presented in the document investigates the biomimetic oxidation of 1,2-diols using molecular oxygen in the presence of iron-porphyrin catalysts, mimicking the function of metal-containing oxidases and oxygenases found in biological systems. The researchers utilized a catalytic system comprising an iron-porphyrin complex, 1-benzyl-3-carbamoyl-1,4-dihydropyridine (BNAH), and molecular oxygen to selectively cleave the carbon-carbon bonds of aryl-substituted ethane-1,2-diols at room temperature, producing aldehydes or ketones as the main oxidation products. The reaction rates were influenced by the steric hindrance of substituents in both the catalysts and diols, and no significant differences in reactivities were observed between the two stereoisomers (meso and dl) of the diols. The study provides insights into the mechanism of the diol cleavage reaction, which involves the initial binding of the diol to the active catalyst forming an intermediate complex, followed by a rate-determining breakdown step in the catalytic cycle. The findings have implications for understanding the activation of molecular oxygen and oxygen atom transfer to organic substrates, processes that are crucial for cytochrome P-450 in biological systems.
10.1021/jacs.6b07230
The study focuses on using ynamides as novel racemization-free coupling reagents for amide and peptide synthesis under mild conditions. It introduces a two-step, one-pot synthetic strategy where ynamides facilitate the hydroacyloxylation of carboxylic acids followed by aminolysis, enabling efficient amide bond formation without the need for protecting functional groups like -OH, -SH, and ArNH2. The methodology highlights the advantages of ynamides in avoiding racemization, especially in peptide coupling, demonstrating excellent selectivity and broad applicability for various carboxylic acids and amines. The study shows potential for scaling up peptide synthesis, with applications in pharmaceutical and industrial processes.
10.3184/030823410X12674470482572
The study presents a three-component reaction involving alkyl isocyanides, dialkyl acetylenedicarboxylates, and furan-2-carboxylic acid arylidene-hydrazides, which results in the formation of highly functionalized ketenimines. The reaction is characterized by mild conditions, high selectivity, and compatibility with various functional groups. The process is straightforward, occurring at ambient temperature in dichloromethane, and yields the desired dialkyl 2-[N′-arylidene-N-(2-furoyl)hydrazino]-3-(alkyliminomethylene)succinate derivatives in excellent yields. The structures of the products were confirmed through elemental analysis and spectroscopic techniques such as IR, 1H NMR, and 13C NMR. The study also proposes a possible reaction mechanism and discusses the synthetic potential of the ketenimine derivatives produced. This research contributes to the field of organic synthesis by providing a new method for the synthesis of complex molecules using a multicomponent reaction approach.
10.1021/ic000769c
The study presents a novel method for the generation of (imine)Pt(II) compounds by reducing the corresponding Pt(IV)-based imines using carbonyl-stabilized phosphorus ylides, Ph3PdCHCO2R, in nonaqueous media. The chemicals used in the study include Pt(IV) imine complexes, phosphorus ylides, and various solvents such as dichloromethane (CH2Cl2) and ethanol (EtOH). The Pt(IV) imine complexes serve as the starting materials that are reduced to form Pt(II) products, which are of interest due to their potential antitumor activity and their scarcity in the literature. The phosphorus ylides act as reducing agents, facilitating the conversion of Pt(IV) to Pt(II) species under mild conditions without further reduction of the platinum center. Solvents are used to dissolve the reactants and facilitate the reaction, as well as to separate and purify the products through techniques like chromatography. The purpose of these chemicals is to enable the selective synthesis of platinum(II) complexes, which are valuable for coordination chemistry and biological studies, particularly for compounds that cannot be prepared directly from Pt(II) precursors.
10.1055/s-2000-6233
The research aimed to develop a simple and efficient synthesis method for 4-arylchroman-2-ones and 1-arylbenzo[f]chroman-3-ones, which are compounds of interest due to their presence in natural molecules and their potential as intermediates in the preparation of 4-arylcoumarins. The study utilized a Michael reaction involving dihydric or trihydric phenols with p-substituted N-cinnamoylazoles in dichloromethane under reflux conditions, in the presence of a base, DBU. The method was found to be particularly effective for preparing compounds with electron-withdrawing groups and provided moderate to good yields of the desired products. The research concluded that this novel mild procedure is complementary to existing methods and offers a valuable approach for synthesizing these complex molecules. The chemicals used in the process included various phenols, N-cinnamoylazoles, and DBU as a catalyst, with dichloromethane serving as the solvent.
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