Substituent Functional Groups Research Articles

Visible‐Light‐Mediated Amide Synthesis in Deep Eutectic Solvents

AbstractIn the present study, for the first time environmentally friendly deep eutectic solvents (DESs) are used as reaction media to perform an efficient, simple and straightforward photocatalytic amide synthesis at room temperature using thioacids and amines. This method features mild conditions, a broad substrate scope, high yields (≤99%) under ambient conditions with air and moisture tolerance. Moreover, the applied operationally mild reaction conditions tolerate the presence of several different functional group substituents on the amine counterpart. Finally, the developed approach allows the recycling of the reaction medium and catalyst for at least three consecutive cycles without a significant decrease in the reaction yield.

Effect of Substituents on Molecular Reactivity during Lignin Oxidation by Chlorine Dioxide: A Density Functional Theory Study.

Lignin is a polymer with a complex structure. It is widely present in lignocellulosic biomass, and it has a variety of functional group substituents and linkage forms. Especially during the oxidation reaction, the positioning effect of the different substituents of the benzene ring leads to differences in lignin reactivity. The position of the benzene ring branched chain with respect to methoxy is important. The study of the effect of benzene substituents on the oxidation reaction's activity is still an unfinished task. In this study, density functional theory (DFT) and the m062x/6-311+g (d) basis set were used. Differences in the processes of phenolic oxygen intermediates formed by phenolic lignin structures (with different substituents) with chlorine dioxide during the chlorine dioxide reaction were investigated. Six phenolic lignin model species with different structures were selected. Bond energies, electrostatic potentials, atomic charges, Fukui functions and double descriptors of lignin model substances and reaction energy barriers are compared. The effects of benzene ring branched chains and methoxy on the mechanism of chlorine dioxide oxidation of lignin were revealed systematically. The results showed that the substituents with shorter branched chains and strong electron-absorbing ability were more stable. Lignin is not easily susceptible to the effects of chlorine dioxide. The substituents with longer branched chains have a significant effect on the flow of electron clouds. The results demonstrate that chlorine dioxide can affect the electron arrangement around the molecule, which directly affects the electrophilic activity of the molecule. The electron-absorbing effect of methoxy leads to a low dissociation energy of the phenolic hydroxyl group. Electrophilic reagents are more likely to attack this reaction site. In addition, the stabilizing effect of methoxy on the molecular structure of lignin was also found.

Design and electrochemical study of merocyanine dyes: Influence of substituents on the redox behaviors and fouling propensity at ubiquitous electrode surfaces

Investigations into the electrochemical behaviours of merocyanine dyes containing the N-methylbenzothiazolium (Btz) acceptor vinyl linked to phenolic (PhO) donors with electron-donating substituents (chlorine atoms), electron-withdrawing substituents (methoxy groups), or without any substituents at their ortho positions on common glassy carbon electrodes (GCEs), as well as gold and platinum surfaces were performed. It was found that the sensing signals and fouling propensities were heavily dependent on the electrode being used. The inclusion of substituent functional groups also minimized the electrochemical fouling of the dyes and further affected the electron transfer kinetics. The reaction mechanisms of the dyes were examined using electrochemical analysis and DFT computations. For both the Cl2PhOBtz and OMe2PhOBtz (Scheme 1), the radical species underwent a partial rearrangement to form radical species in the ortho position following the loss of the first electron. Following the first electron loss for the PhOBtz (Scheme 1), the formed radical species was unstable and underwent an instantaneous self-coupling reaction with a similar radical species to produce diquinone methide. This resulted in an irreversible oxidation reaction and increased the fouling propensity of the formed species on the electrodes. By understanding the influences of various substituents and taking into consideration of the fouling propensities, reversibility and sensing signals with respect to specific surfaces, novel aptamer-binding merocyanine dyes may be designed and synthesized for the development of highly robust and sensitive electrochemical sensors for medical and environmental applications.

Effect of Nature of Substituents on Coordination Properties of Mono- and Disubstituted Derivatives of Boron Cluster Anions [BnHn]2– (n = 10, 12) and Carboranes with exo-Polyhedral B–X Bonds (X = N, O, S, Hal)

This review systematizes data on the coordination ability of mono- and disubstituted derivatives of boron cluster anions and carboranes in complexation with transition metals. Boron clusters anions [BnHn]2–, monocarborane anions [CBnHn–1]–, and dicarboranes [C2BnHn–2] (with non-functionalized carbon atoms) (n = 10, 12) containing the B–X exo-polyhedral bonds (X = N, O, S, Hal) are discussed. Synthesis and structural features of complexes known to date are described. The effect of complexing metal and substituent attached to the boron cage on the composition and structures of the final complexes is analyzed. It has been established that substituted derivatives of boron cluster anions and carboranes can act as both ligands and counterions. A complexing agent can coordinate substituted derivatives of the boron cluster anions due to three-center two-electron 3c2e MHB bonds, by the substituent functional groups, or a mixed type of coordination can be realized, through the BH groups of the boron cage and the substituent. As for B-substituted carboranes, complexes with coordinated substituents or salts with non-coordinated carborane derivatives have been isolated; compounds with MHB bonding are not characteristic of carboranes.

Directing excited state dynamics via chemical substitution: A systematic study of π-donors and π-acceptors at a carbon-carbon double bond.

Functional group substituents are a ubiquitous tool in ground-state organic chemistry often employed to fine-tune chemical properties and obtain desired chemical reaction outcomes. Their effect on photoexcited electronic states, however, remains poorly understood. To help build an intuition for these effects, we have studied ethylene, substituted with electron acceptor (cyano) and/or electron donor (methoxy) substituents, both theoretically and experimentally: using ab initio quantum molecular dynamics and time-resolved photoelectron spectroscopy. Our results show the consistent trend that photo-induced ethylenic dynamics is primarily localized to the carbon with the greater electron density. For doubly substituted ethylenes, the trend is additive when both substituents are located on opposite carbons, whereas the methoxy group (in concert with steric effects) dominates when both substituents are located on a single carbon atom. These results point to the development of rules for structure-dynamics correlations; in this case, a novel mechanistic ultrafast photochemistry for conjugated carbon chains employing long-established chemical concepts.

Copper-Catalyzed Direct C(sp3)-H Alkoxylation to Access Quaternary α-Alkoxylated Amino Acid Derivatives.

A copper-catalyzed C(sp3)-H alkoxylation was developed to prepare quaternary α-alkoxylated amino acid derivatives in good yields. This protocol can be applied to a series of α-amino acids bearing a variety of functional group substituents. Facile removal of the auxiliary directing group and tolerance of condensation conditions for amide bond formation enable the potential application of this method in the discovery of new peptide drugs in the future.

The 1α-hydroxy-A-rings of norditerpenoid alkaloids are twisted-boat conformers

The skeletal conformations of naturally occurring norditerpenoid alkaloids fix their substituent functional groups in space, thereby directing their bioactivities. Solution conformations of the A-rings of 4 selected norditerpenoid alkaloid free bases: mesaconitine, karacoline (karakoline), condelphine, and neoline (bullatine B), were analysed by NMR spectroscopy and single-crystal X-ray crystallography. They adopt twisted-chair, twisted-boat, twisted-boat, twisted-boat conformations, respectively. That the A-ring is stabilised in a boat conformer by an intramolecular H-bond from 1α-OH to the N-ethyl tertiary amine is also confirmed in the condelphine single crystal data. The conformations are a result of through-space repulsion between 12-He′ and atoms attached to C1 (in the equatorial positions). This causes the A-rings with 1α-OR always to be twisted whether in a chair or a boat conformation. The impact of these studies is in providing a detailed understanding of the shape of the A-ring of these important biologically active natural product alkaloids.

Access to Bicyclo[4.2.0]octene Monomers To Explore the Scope of Alternating Ring-Opening Metathesis Polymerization.

Bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides undergo alternating ring-opening metathesis polymerization (AROMP) with cyclohexene. Herein, a general method for the preparation of bicyclo[4.2.0]oct-(8)-ene-8-carboxy derivatives is described. The central 8-cyano intermediate provides entry to five different functional group substituents on the alkene. These monomers were tested as potential substrates for AROMP with cyclohexene. In addition to the carboxamide, the carboxynitrile and carboxaldehyde are also substrates for AROMP. In the case of the carboxaldehyde, the polymer is regioregular. However, the addition of carboxynitrile is stereoirregular and slow.

Surface-modified TiO2 powders with phenol derivatives: A comparative DFT and experimental study

The charge transfer complex formation between TiO2 powder and variety of phenol derivatives (phenol, 4-nitrophenol, 4-bromophenol, 4-tert-butylphenol, hydroquinone) was achieved. The red-shift of optical absorption was observed upon surface modification of TiO2 powders with phenol derivatives. The influence of substituent functional groups in para position on the optical band gap and conduction band edge of inorganic/organic hybrids was studied using reflection spectroscopy and cyclic voltammetry. The experimental findings were supported by density functional theory calculations. The measured reflection spectra of surface-modified TiO2 powders with phenol derivatives were compared with calculated electronic excitation spectra of corresponding model systems.

Evaluation of ecotoxicological effects of benzophenone UV filters: Luminescent bacteria toxicity, genotoxicity and hormonal activity

The widespread use of organic ultraviolet (UV) filters in personal care products raises concerns about their potentially hazardous effects on human and ecosystem health. In this study, the toxicities of four commonly used benzophenones (BPs) UV filters including benzophenone (BP), 2-Hydroxybenzophenone (2HB), 2-Hydroxy-4-methoxybenzophenone (BP3), and 2-Hydroxy-4-methoxybenzophenone-5-sulfonicacid (BP4) in water were assayed in vitro using Vibrio fischeri, SOS/umu assay, and yeast estrogen screen (YES) assay, as well as in vivo using zebrafish larvae. The results showed that the luminescent bacteria toxicity, expressed as logEC50, increased with the lipophilicity (logKow) of BPs UV filters. Especially, since 2HB, BP3 and BP4 had different substituent groups, namely -OH, -OCH3 and -SO3H, respectively, these substituent functional groups had a major contribution to the lipophilicity and acute toxicity of these BPs. Similar tendency was observed for the genotoxicity, expressed as the value of induction ratio=1.5. Moreover, all the target BPs UV filters showed estrogenic activity, but no significant influences of lipophilicity on the estrogenicity were observed, with BP3 having the weakest estrogenic efficiency in vitro. Although BP3 displayed no noticeable adverse effects in any in vitro assays, multiple hormonal activities were observed in zebrafish larvae including estrogenicity, anti-estrogenicity and anti-androgenicity by regulating the expression of target genes. The results indicated potential hazardous effects of BPs UV filters and the importance of the combination of toxicological evaluation methods including in vitro and in vivo assays.

Antitumor Exopolysaccharides Derived from Novel Marine Bacillus: Isolation, Characterization Aspect and Biological Activity

Objective:Exopolysaccharides gained attention as new source for cancer treatment as recent treatments cause side effects and multidrug resistance. Polysaccharides containing sulfur and uronic acids exhibited antioxidant activity, by restoring cell redox regulation, thus inhibiting cell proliferation and cancer formation. Following this context, our study was performed to assess the cytotoxic activity of exopolysaccharides produced by novel Egyptian marine bacterial strains on HepG2 cells.Methods:Bacteria were isolated, purified and cultured through routine microbiological techniques. 16S rRNA gene amplification and sequence analyses, Fourier Transform Infra-red (FTIR), Identification of monosugars by HPLC molecular weight estimation, sulfur content determination and neutral red uptake assay were utilized.Results:BLAST showed that the isolates were related to the Bacillus sp. FTIR analysis indicated that the four EPSs under study contained sulfur as substituent functional group but with different percentage in each EPS. The highest sulfur percentage (46%) appeared in the EPS-6 that was produced by Bacillus flexus isolated from the Mediterranean Sea. HPLC showed that EPSs contained uronic acids which appeared as glucuronic and galacturonic acid in the low molecular weight EPS-6 (4.296×104 g mol-1). Arabinose appeared besides the glucuronic and galacturonic acid residues. EPS-6 showed the highest cytotoxicity, IC50 (218 µg ml-1) which could be correlated to the presence of sulfure and uronic acids in its structure.Conclusion:The novel Firmicutes from the Egyptian saline habitat produced EPSs of cytotoxic activity on hepatocellular carcinoma.

ВПЛИВ Eu(fod)3 НА СПЕКТРИ 1Н ЯМР 3-АРИЛІЗОКУМАРИНІВ ТА 3-АРИЛ-3,4 ДИГІДРОІЗОКУМАРИНІВ З АЛКОКСИЛЬНИМИ, ЕСТЕРНИМИ ТА АМІДНИМИ ГРУПАМИ

The effect of the lanthanide shift reagent (LSR) – tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octa-dionate) of Europium – Eu(fod)3 – on 1H NMR spectra of functionalized 3-arylisocoumarins and 3-aryl-3,4-dihydroisocoumarins was investigated. Based on previous studies of LSR interactions with benzopyrones, it was expected that the main coordination centre for the Eu3+ would be the exocyclic Oxygen atom of the heterocycle, but the possibility of competition from aromatic substituent functional groups was also considered. By measuring lanthanide-induced shifts (LIS) of the proton signals of the molecules at different ratios of substrate and Eu(fod)3, specific LIS values were determined. Based on those, it was concluded that the main direction of LSR coordination with 3-(2-hydroxy-5-methylphenyl)-1Hisochromen-1-one, 3-(2-methoxy-5-methylphenyl)-1H-isochromen-1-one and 3-(2-methoxy-5-methylphenyl)isochroman-1-one is the exocyclic Oxygen atom of the heterocycle, because the maximum LIS were recorded for the H-8 atom of isochromone system of these derivatives. In the case of ethyl ester of [2-(4-(1-oxo-1H-isochromen-3-yl)phenoxy] acetic acid and methyl ester of [2-(4-(1-oxoisochroman-3-yl)phenoxy]acetic acid comparable LIS values were observed both for H-8 and for the methylene group of the hydroxyacetic acid fragment, therefore, in such molecules the coordination of the Eu3+ to the heterocycle or to the aliphatic ester group is almost equally probable. In spectrum of methyl ester of N-{[4-(1-oxo-1H-isochromen-3-yl)phenoxy]acetyl}valine and N-{[4-(1-oxoisochroman-3-yl)-phenoxy]acetyl}valine there are insignificant LIS of H-8; and the maximum LIS were observed for the signals of the protons neighboring the two carbonyl groups of hydroxyacetic acid and valine fragments. Thus, these compounds interact w

Correlating photoacidity to hydrogen-bond structure by using the local O-H stretching probe in hydrogen-bonded complexes of aromatic alcohols.

To assess the potential use of O-H stretching modes of aromatic alcohols as ultrafast local probes of transient structures and photoacidity, we analyze the response of the O-H stretching mode in the 2-naphthol-acetonitrile (2N-CH3CN) 1:1 complex after UV photoexcitation. We combine femtosecond UV-infrared pump-probe spectroscopy and a theoretical treatment of vibrational solvatochromic effects based on the Pullin perturbative approach, parametrized at the density functional theory (DFT) level. We analyze the effect of hydrogen bonding on the vibrational properties of the photoacid-base complex in the S0 state, as compared to O-H stretching vibrations in a wide range of substituted phenols and naphthols covering the 3000-3650 cm(-1) frequency range. Ground state vibrational properties of these phenols and naphthols with various substituent functional groups are analyzed in solvents of different polarity and compared to the vibrational frequency shift of 2N induced by UV photoexcitation to the (1)Lb electronic excited state. We find that the O-H stretching frequency shifts follow a linear relationship with the solvent polarity function F0 = (2ε0 - 2)/(2ε0 + 1), where ε0 is the static dielectric constant of the solvent. These changes are directly correlated with photoacidity trends determined by reported pKa values and with structural changes in the O···N and O-H hydrogen-bond distances induced by solvation or photoexcitation of the hydrogen-bonded complexes.

A New Bifunctional Electrochemical Sensor for Hydrogen Peroxide and Nitrite Based on Bimetallic Porphyrin MOF

Metalloporphyrin molecules are excellent candidates to act as molecular building blocks for the construction of MOFs, because of various functional group substituents in the periphery of the molecule and the huge variety of available derivatives incorporating different centre-coordinated metals.[1] in this work, a new bimetallic porphyrin MOF, [Cu2(Co-TCPP)(H2O)2]·0.5DMF·5H2O (Cu-CoTCPP), consisting of [5,10,15,20-(4-carboxy-phenyl)porphyrin]Co(II) (CoTCPP) struts which were bound by Cu(II)-carboxylate clusters (Cu2(COO)4), was prepared solvothermally and characterized by various techniques, including XRD, IR, elemental analysis, TG, and TEM. Cu-CoTCPP showed novel bifunctional electrocatalytic ability toward both the reduction of H2O2 and the oxidation of NaNO2 which might be due to Cu and Co, respectively. With the assistance of multi-walled carbon nanotubes (MWNTs), Cu-CoTCPP showed greatly improved sensing performance in the determination of H2O2 and NaNO2. Cu-CoTCPP/MWNTs/GCE also showed fast response, and high selectivity, steadiness and reproducibility. Excellent determination performance and high biocompatibility make the metalloporphyrin functionalized MOFs promising in electrochemical biosensing. Keywords: porphyrin MOF , bimetallic, electrochemical sensing [1] LI, Q. W., ZHANG, W. Y., MILJANIC, O. S., SUE, C. H., ZHAO, Y. L., LIU, L. H., KNOBLER, C. B., STODDART, J. F. & YAGHI, O. M. 2009. Docking in Metal-Organic Frameworks. Science, 325, 855-859. The authors thank National Natural Science Foundation of China (Grant No. 21175068) for the financial support.

ChemInform Abstract: Iron(III)‐Catalyzed Aerobic Oxidation and Cleavage/Formation of a C—S Bond.

A new iron(III)-catalyzed synthesis of beta-oxo sulfones is described that employs vinylarenes and readily available dimethyl sulfoxide (DMSO) with hydrazine and oxygen as the oxidant. The reaction tolerates various functional group substituents on the vinylarene substrates to afford beta-oxo sulfones in moderate to good yields. The cleavage and formation of the C-S bond are the key steps of this transformation.

Iron(III)‐Catalyzed Aerobic Oxidation and Cleavage/Formation of a C–S Bond

AbstractA new iron(III)‐catalyzed synthesis of β‐oxo sulfones is described that employs vinylarenes and readily available dimethyl sulfoxide (DMSO) with hydrazine and oxygen as the oxidant. The reaction tolerates various functional group substituents on the vinylarene substrates to afford β‐oxo sulfones in moderate to good yields. The cleavage and formation of the C–S bond are the key steps of this transformation.

Comparative binding affinities of flavonoid phytochemicals with bovine serum albumin.

Dietary flavonoids show beneficial effects in the prevention of chronic diseases. However, flavonoid bioavailability is poor, probably due to their interaction with serum albumins. In the current work, the binding interactions of eight related flavonoids, sharing a similar core structure, with bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. The binding affinities of the flavonoids with BSA were in the order hesperetin (KA=5.59 × 10(5))> quercetin (4.94 × 10(5)) > naringenin (3.04 × 10(5)) > isoquercitrin (4.66 × 10(4)) > icariin (3.60 × 10(4)) > rutin (1.65 × 10(4)) > hesperidin (2.50 × 10(3)) > naringin (8.70 × 10(2)). The associations of specific structural components of the flavonoids with their binding properties to BSA were also explored and hydrophobicity, functional group substituents, steric hindrance effects and the spatial arrangements of substituents seem to be the key factors for the affinities of flavonoids towards BSA. The results from the current work contribute to a better understanding of the transport of flavonoids in plasma and helping predict their physiological functions based on their intrinsic structures.

MICROCHEMICAL DIFFERENTIATION OF CONODONT AND SCOLECODONT MICROFOSSILS

Conodonts and scolecodonts are common Paleozoic microfossils that are often used to determine the geothermometry of Paleozoic sequences. The two fossils, which can be difficult morphologically to distinguish one from the other, undergo a different thermal alteration pathway. In this study, Fourier transform infrared (FTIR) spectroscopy of scolecodont and conodont microfossils from the Woodford Shale of southern Oklahoma, United States, confirmed they have different chemical compositions. Infrared (IR) spectra acquired from conodonts show a predominance of an inorganic carbonated hydroxylapatite (CO3OHAp) with a minor organic composition of aliphatic hydrocarbon, containing carbonyl substituent functional groups. In contrast, IR spectra acquired from scolecodonts show no inorganic mineralogy but instead confirm that these microfossils are composed of organic material consisting of an aliphatic and aromatic hydrocarbon network with ether linkages and carbonyl substituent functional groups. These data reveal that scolecodont elements can easily be distinguished from conodont elements with FTIR microspectroscopy due to their different chemical compositions. This study provides future fossil workers with a viable method to independently identify enigmatic toothlike microfossils that cannot confidently be assigned to either scolecodont or conodont groups by morphology alone.

High-Resolution Zero-Field NMR J-Spectroscopy of Aromatic Compounds

We report the acquisition and interpretation of nuclear magnetic resonance (NMR) J-spectra at zero magnetic field for a series of benzene derivatives, demonstrating the analytical capabilities of zero-field NMR. The zeroth-order spectral patterns do not overlap, which allows for straightforward determination of the spin interactions of substituent functional groups. Higher-order effects cause additional line splittings, revealing additional molecular information. We demonstrate resonance linewidths as narrow as 11 mHz, permitting resolution of minute frequency differences and precise determination of long-range J-couplings. The measurement of J-couplings with the high precision offered by zero-field NMR may allow further refinements in the determination of molecular structure and conformation.

Structure-Activity Relationship Analysis of the Thermal Stabilities of Nitroaromatic Compounds Following Different Decomposition Mechanisms.

The decomposition behavior of energetic materials is very important for the safety problems concerning their production, transportation, use and storage, because molecular decomposition is intimately connected to their explosive properties. Nitroaromatic compounds, particularly nitrobenzene derivatives, are often considered as prototypical energetic molecules, and some of them are commonly used as high explosives. Quantitative structure-activity relationship (QSAR) represents a potential tool for predicting the thermal stability properties of energetic materials. But it is reported that constructing general reliable models to predict their stability and their potential explosive properties is a very difficult task. In this work, we make our efforts to investigate the relationship between the molecular structures and corresponding thermal stabilities of 77 nitrobenzene derivatives with various substituent functional groups (in ortho, meta and/or para positions). The proposed best MLR model, developed by the new software QSARINS, based on Genetic Algorithm for variable selection and with various validation tools, is robust, stable and predictive with R(2) of 0.86, QLOO (2) of 0.79 and CCC of 0.90. The results indicated that, though difficult, it is possible to build predictive, externally validated QSAR models to estimate the thermal stability of nitroaromatic compounds.