Substituted Benzene Derivatives Research Articles

Plasmon-Mediated Organic Photoelectrochemistry Applied to Amination Reactions.

Organic electrochemistry is currently experiencing an era of renaissance, which is closely related to the possibility of carrying out organic transformations under mild conditions, with high selectivity, high yields, and without the use of toxic solvents. Combination of organic electrochemistry with alternative approaches, such as photo-chemistry was found to have great potential due to induced synergy effects. In this work, we propose for the first time utilization of plasmon triggering of enhanced and regio-controlled organic chemical transformation performed in photoelectrochemical regime. The advantages of the proposed route is demonstrated in the model amination reaction with formation of C-N bond between pyrazole and substituted benzene derivatives. Amination was performed in photo-electrochemical mode on the surface of plasmon active Au@Pt electrode with attention focused on the impact of plasmon triggering on the reaction efficiency and regio-selectivity. The ability to enhance the reaction rate significantly and to tune products regio-selectivity is demonstrated. We also performed density functional theory calculations to inquire about the reaction mechanism and potentially explain the plasmon contribution to electrochemical reaction rate and regioselectivity.

ISOLATION OF SITOSTEROL AND STIGMASTEROL FROM THE ROOTS OF CROTON PENDULIFLORUS

The primary aim of this study was to isolate Sitosterol from the root of Croton Penduliflorus. Croton Penduliflorus Hutch (Euphorbiaceae) commonly known as Turk’s Cap though to originate from Malaysia, is a tropical evergreen plant widely distributed in the southern part of Nigeria. It is employed in folklore medicine both as drastic and fugitive, as well as a psychotropic medicinal plant. It is also credited with antimicrobial, antivenom, antiparalytical, rubefacient and anti-tumor potencies Extraction of the roots of Croton Penduliflorus with ethanol and partitioning of the extract with hexane, chloroform and ethyl acetate followed by column chromatography of the chloroform extract has led to the isolation of sitosterol, stigmasterol and a substituted benzene derivative. Their structures were established using 1D and 2D NMR, LCMS, and FTIR spectral analysis and a comparison of their spectral data with literature reports.

Modular Access tometa-Substituted Benzenes via Mo-Catalyzed Intermolecular Deoxygenative Benzene Formation

The substituted benzene derivatives are essential to organic synthesis, medicinal chemistry, and material science. However, the 1,3-di- and 1,3,5-trisubstituted benzenes are far less prevalent in small-molecule drugs than other substitution patterns, likely due to the lack of robust, efficient, and convenient synthetic methods. Here, we report a Mo-catalyzed intermolecular deoxygenative benzene-forming reaction of readily available ynones and allylic amines. A wide range of unsymmetric and unfunctionalized 1,3-di- and 1,3,5-trisubstituted benzenes were obtained in up to 88% yield by using a commercially available molybdenum catalyst. The synthetic potential of the method was further illustrated by synthetic transformations, a scale-up synthesis, and derivatization of bioactive molecules. Preliminary mechanistic studies suggested that this benzene-forming process might proceed through a Mo-catalyzed aza-Michael addition/[1,5]-hydride shift/cyclization/aromatization cascade. This strategy not only provided a facile, robust, and modular approach to various meta-substituted benzene derivatives but also demonstrated the potential of molybdenum catalysis in the challenging intermolecular deoxygenative cross-coupling reactions.

Ferroelectricity and Phase Change Memory of Bis(tetradecylamide)-Substituted Benzene Derivatives

Interplay between intermolecular interactions including hydrogen bonding, halogen–halogen, and van der Waals interactions in molecular crystals leads to diverse phase transition behaviors and physical properties. Bis(tetradecylamide)-substituted benzene derivatives, terephthalamide (C14-TPA), isophthalamide (C14-IPA), and phthalamide (C14-PA), were examined, and the electric field–polarization curves of the former two crystals indicated ferroelectric hysteresis behavior in high-temperature solid phases. C14-XIPA derivatives where X = CH3, Cl, Br, or I at the 5-position of the IPA molecule were synthesized, and the effects of substituent X on the molecular assembly structure and physical properties were investigated. H- and CH3-substituted C14-IPA and C14-MeIPA formed a crystalline phase in which intermolecular amide-type N–H···O═ hydrogen-bonding interactions were dominant, whereas halogen-substituted C14-XIPAs formed a metastable glass phase upon cooling from the isotropic liquid. The formation of the glass phase is associated with energy competition between hydrogen bonding, halogen–halogen, and van der Waals interactions among the −CONH–, −X, and −CnH2n+1 units. The glass-crystal phase transition of C14-XIPAs (X = Cl, Br, or I) changes the refractive index under polarized optical microscopic observation, which can be utilized for phase-change memory.

A Novel Antibacterial Component and the Mechanisms of an Amaranthus tricolor Leaf Ethyl Acetate Extract against Acidovorax avenae subsp. citrulli.

The aim of the present investigation was to determine the active ingredients in Amaranthus tricolor L. leaves and develop a biological pesticide. Organic solvent extraction, column chromatography, liquid chromatography, ODS-C18 reverse elution, Sephadex LH-20 gel filtration, H spectrum, and C spectrum were used to isolate the pure product for an assessment of the agricultural activity and bacteriostatic mechanisms. The results showed that the activity of the crude extract following carbon powder filtration was 1.63-fold that of the non-filtered extract. Further isolation was performed to obtain two pure products, namely, hydroxybenzoic acid (HBA) and benzo[b]furan-2-carboxaldehyde (BFC), and their molecular formulas and molecular weights were C7H6O3 and 138.12, and C9H6O2 and 146.12, respectively. Our study is the first to determine that HBA has bacteriostatic activity (MIC 125 μg/mL) and is also the first to isolate BFC from A. tricolor. The ultrastructure observation results showed that HBA caused the bacteria to become shriveled, distorted, and deformed, as well as exhibit uneven surfaces. After HBA treatment, 70 differentially expressed metabolites were detected in the bacteria, of which 9 were downregulated and 61 were upregulated. The differentially expressed metabolites were mainly strigolactones, organic acids and derivatives, fatty acids, benzene and substituted benzene derivatives, amino acids and associated metabolites, and alcohols and amines. Among all of the downregulated differentially expressed metabolites, MEDP1280 was the most critical, as it participates in many physiological and biochemical processes. The enrichment analysis showed that the differentially expressed metabolites mainly participate in tyrosine metabolism, biosynthesis of amino acids, cysteine and methionine metabolism, and arginine and proline metabolism. Additionally, HBA was found to disrupt cell membrane permeability and integrity, causing the leakage of substances and apoptosis. The physiological and biochemical test results showed that HBA could increase the pyruvate levels in bacteria but could decrease the activities of respiratory enzymes (malate dehydrogenase (MDH) and NADH oxidase) and antioxidant enzymes (superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX)). Inverse molecular docking was used to study the binding between HBA and respiratory and antioxidant enzymes. The results showed that HBA could bind to MDH, NADH oxidase, SOD, and GSH-PX, suggesting that these enzymes may be the effector targets of HBA. Conclusion: The optimal active ingredient in A. tricolor that can inhibit Acidovorax avenae subsp. citrulli was identified as HBA. HBA mainly disrupts the cell membrane, damages the metabolic system, and inhibits respiration and antioxidant enzyme activity to control bacterial growth. These results provide a reference for the further development of biological pesticides.

Construction of N-Heterocycles Fused with a Highly Substituted Benzene Ring by a Benzyne-Mediated Cyclization/Functionalization Cascade Reaction and Its Application to the Total Synthesis of Marine Natural Products.

This account summarizes the development of a benzyne-mediated cyclization/functionalization protocol for the versatile construction of highly substituted benzene derivatives fused with an N-heterocyclic ring such as indolines, indoles, and related nitrogen-containing heterocycles. The protocol comprises sequential reactions initiated by generating a benzyne species and subsequent cyclization via addition of magnesium amide to the benzyne, followed by trapping of the resultant magnesium compound in situ with various electrophiles. The substituent scope was expanded by conducting a transmetalation on a copper species to introduce alkyl, aryl, and alkenyl substituents. The utility of the sequential reaction was demonstrated in the synthesis of a carbazole natural product (heptaphylline), pyrrolo[4,3,2-de]quinoline alkaloids (batzellines), and pyrrolo[2,3-c]carbazole alkaloids (dictyodendrines).

Two-Color Resonant Two-Photon Mass-Analyzed Threshold Ionization of 2,4-Difluoroanisole and the Additivity Relation of Ionization Energy.

We used the two-color resonant two-photon ionization and mass-analyzed threshold ionization spectroscopic techniques to record the vibronic, photoionization efficiency, and cation spectra of 2,4-difluoroanisole. The cation spectra were obtained through ionization via seven intermediate vibronic states, which involved out-of-plane ring-F, in-plane ring-F, and ring-OCH3 bending vibrations as well as in-plane ring deformation vibrations. The band origin of the S1 ← S0 electronic transition of 2,4-difluoroanisole appeared at 35 556 ± 2 cm-1, and the adiabatic ionization energy was determined to be 67 568 ± 5 cm-1. The experimental data provided information on the active vibrations of aforementioned compound in the electronically excited state S1 and ground cationic state D0. A comparison of the experimental data obtained for 2,4-difluoroanisole in this study with the data obtained for other fluorine-substituted benzenes in previous studies indicated that the nature, location, and number of substituents influence electronic transition energy, ionization energy, and molecular vibration. In addition, a simple additivity relation might exist for predicting the ionization energy of multiply substituted benzene derivatives.

C–O/C–S difunctionalized benzene derivatives via multicomponent coupling of tetraynes

C–O/C–S difunctionalization of fused highly substituted benzene derivatives was conducted via the multicomponent coupling reaction of tetraynes, sulfoxides, and cyclopropenones.

Qualitative as well as quantitative analysis of interactions present in chlorine and bromine substituted aromatic organic crystals: A DFT linked Crystal Explorer study

The effect of noncovalent interactions in shaping a crystal structure is explored qualitatively as well as quantitatively in a DFT linked Crystal Explorer (CE) study of nine different Chlorine and Bromine substituted benzene derivatives. The qualitative approach to analyze interactions is based on Hirshfeld surface that locates electronic charge distribution on the surface, quantitative estimation is obtained by linking DFT computations withCE.In the halogen substituted benzene derivatives considered here, in addition to conventional hydrogen and halogen bonding other interactions such as those between Chlorine–Hydrogen, Bromine–Hydrogen, Bromine-Oxygen have been deciphered. The molecular crystal structure of a variety of halogen substituted aromatic molecules has been rationalized and attributed to specific interactions.

The use of Mixed Bacterial Culture to improve the Biodegradation of Diesel Pollution

This study was conducted to evaluate the hydrocarbon biodegradation abilities of Enterobacter cloacae, Staphylococcus aureus, Sphingomonas paucimobilis, and Pentoae species which were isolated from different diesel-contaminated soil samples. The isolates were identified by the Vitek 2 system. Fourier-transform spectroscopy (FT-IR) tested the potential of these isolates to biodegrade the diesel according to the peak areas, a significant decrease in the area of the peaks at 2856-2928 cm−1 corresponds to aliphatic hydrocarbons. The appearance of small peaks at 900-1032 cm−1 refers to substituted benzene derivative compounds. An appearance of some new peaks at 3010- 3030 cm−1 which indicate the presence of alcohol (-OH) and ketones (RC=O). A sharp peak appeared at 1712 cm−1 refers to the carbonyl group (C=O). The potential of biological surfactant production was tested using the Sigma 703D stand-alone tensiometer showed that these isolates were biological surfactant producers. The better results of the surface tension reduction test were obtained when using the mixed bacterial culture which reduced the surface tension of the medium from 66 mN/m to 35.15 mN/m. Single isolates and mixed bacterial culture have investigated their ability to degrade 3.0 % (v/v) of diesel as sole source of carbon and energy in Bushnell- Haas medium. The results demonstrated that the bacterial isolates could be effective in biodegradation of diesel spills individually and showed good biodegradation abilities when they are used together in the mixed bacterial culture.

Influence of aromatic hydrocarbons on growth, plant growth promoting activities and survival in soil of Azotobacter chroococcum strain JL104

This study was undertaken to determine the effect of aromatic hydrocarbons on growth and plant growth promoting activities of Azotobacter chroococcum strain JL104. The organism was grown on Jensen’s media without sucrose, supplemented with different concentrations of aromatic hydrocarbons. Azotobacter chroococcum strain JL104 was able to grow in the presence of benzene, toluene, aniline and benzoic acid and was able to utilize these as sole carbon source as well. The culture showed the highest growth in presence of 0.5% concentrations of aniline and benzoic acid and 0.01% concentrations of benzene and toluene. Maximum indole acetic acid (IAA) production and acetylene reduction activity (ARA) were recorded with benzene and benzoic acid, respectively. Among other substituted benzene derivatives such as xylene, p-hydroxybenzoic acid, di-nitrophenol and di-chlorophenol, xylene was observed to be the least toxic and di-nitrophenol the most toxic hydrocarbon. The highest soil survival was found in soil amended with 1% sucrose however, the population of A. chroococccum strain JL104 declined continuously in unamended soil. Amongst various hydrocarbons, 0.1% toluene amended soil supported the maximum survival, indicating it to be least toxic aromatic hydrocarbon carbon in soil.

Hydrophobicity versus electrophilicity: A new protocol toward quantitative structure-toxicity relationship.

QSAR/QSPR/QSTR modeling and chemical grouping approach are presented to provide information on the biological properties of various substituted benzene derivatives. A novel descriptor, viz., the square of electrophilicity index (ω2 ) is proposed to provide a compact correlation between the structure of the compounds and their biological properties which is marginally superior to electrophilicity index (ω) or ω3 in most of the cases, and more or less similar to that obtained from hydrophobicity (or lipophilicity). Besides the straightforward case study, neural networks (NN) are employed to ascertain the robustness of the QSAR model obtained by implementing multiple linear regression (MLR).

Synthesis of Benzofused N-Heterocycles via Rh(III)-Catalyzed Direct Benzannulation with 1,3-Dienes

Benzofused nitrogen heterocycles are prevalent as key core structural motifs in functional molecules. Major syntheses of benzofused nitrogen heterocycles focus on construction of the heterocyclic ring starting from (poly)substituted benzene derivatives. Given that polysubstituted benzene derivatives are not always easily available, the flexibility of these methods may be problematic. The direct benzannulation reactions of simple N-heterocycles thus provide a complementary and valuable strategy. However, this approach has been far less explored, especially when nonprefunctionalized N-heterocycles are used as starting materials. In recent years, the metal-catalyzed direct functionalization of an inert C–H bond has become a powerful tool to construct (hetero)aromatics. In the C–H benzannulation reactions, alkynes, activated alkenes, enaldiazo compounds, and biaryl compounds were previously utilized as efficient coupling partners. Reported herein is a de novo synthesis of a benzene ring through the rhodium-ca...

Design of Protein-Based Biosensors for Selective Detection of Benzene Groups of Pollutants.

Benzene and its derivatives form a class of priority pollutants whose exposure poses grave risk to human health. Since benzene lacks active functional groups, devising specific sensors for its direct detection from a milieu of aromatics has remained a daunting task. Here, we report three engineered protein-based biosensors that exclusively and specifically detect benzene and its derivatives up to a detection limit of 0.3 ppm. Further, the biosensor design has been engineered to create templates that possess the ability to specifically discriminate between alkyl substituted benzene derivatives; such as toluene, m-xylene, and mesitylene. Interference tests with simulated wastewater samples reveal that the engineered biosensors can selectively detect a specific benzene compound in water samples containing a milieu of high concentrations of commonly occurring pollutants. This work demonstrates the potential of structure guided protein engineering as a competent strategy toward design of selective biosensors for direct detection of benzene group of pollutants from real time environmental samples.

Abraham model correlations for describing the thermodynamic properties of solute transfer into pentyl acetate based on headspace chromatographic and solubility measurements

Abstract Infinite dilution activity coefficients were measured for 32 liquid organic solutes dissolved in pentyl acetate at 298.15 K. The organic solutes included both saturated (hexane through decane, cyclohexane) and unsaturated hydrocarbons (1-hexene, 1-heptene, cyclohexene, 1-octyne, 1,7-octadiene), several substituted benzene derivatives (benzene, methylbenzene, ethylbenzene, propylbenzene, 1,3-dimethylbenzene, 1-dimethylbenzene, fluorobenzene, bromobenzene), four haloalkanes (trichloromethane, 1-chlorobutane, 1,2-dichloropropane, isopropyl bromide) and three alcohols (ethanol, 1-propanol, 2-propanol), as well six miscellaneous organic compounds (acetonitrile, ethyl acetate, tetrahydrofuran, 1,4-dioxane, propanone, nitromethane). Mole fraction solubilities were also determined for 10 crystalline nonelectrolyte organic solutes dissolved in pentyl acetate. Results of the experimental measurements were used to derive Abraham model correlations for describing thermodynamic properties of solute transfer into pentyl acetate. The derived Abraham model correlations mathematically described the observed data to within 0.12 log units (or less).

Aromaticity of benzene derivatives: an exploration of the Cambridge Structural Database.

The harmonic oscillator model of aromaticity (HOMA) index, one of the most popular aromaticity indices for solid-state benzene rings in the Cambridge Structural Database (CSD), has been analyzed. The histograms of HOMA for benzene, for benzene derivatives with one formyl, nitro, amino or hydroxy group as well as the histograms for the derivatives with two formyl, nitro, amino or hydroxy groups in ortho, meta and para positions were investigated. The majority of the substituted benzene derivatives in the CSD are characterized by a high value of HOMA, indicating fully aromatic character; however, the distribution of the HOMA value from 1 to about 0 indicates decreasing aromaticity down to non-aromatic character. Among the benzene derivatives investigated, a significant decrease in aromaticity can be related to compounds with diamino and dinitro groups in the meta position.

Tuning Aromaticity of para-Substituted Benzene Derivatives with an External Electric Field.

Substituent effects are phenomena which play an important role in organic chemistry, especially when aromatic species are considered. For this class of systems, the question of the interrelation between substituent effect and aromaticity arises. The relationship between aromaticity and substituent effects appears to be of a competitive nature. This work examines changes in aromaticity in para-substituted benzene derivatives exposed to external electric fields of various intensities. Three systems with different substituent electron-accepting/donating properties are studied, namely p-aminophenol, p-nitrobenzonitrile and p-nitrophenol. In these cases, the competitive character between substituent effects and aromaticity is emphasised. It is also shown that aromaticity (and the substituent effect) can be tuned using an external electric field applied to the system.

Excited state dynamics of molecules studied with femtosecond time-resolved mass spectrometry and photoelectron imaging

Study of quantum states of molecules, especially the evolution of excited states can help to understand their basic features and the interactions among different states. Furthermore, the information about the chemical reaction process and the interactions among several reaction channels can be obtained. Femtosecond time-resolved mass spectrometry (TRMS) and time-resolved photoelectron imaging (TRPEI), which combine pump-probe technique with time of flight mass spectrometry and photoelectron imaging, are powerful tools for detecting the molecular quantum state and for studying the molecular quantum state interaction and molecular ultrafast dynamics. With these methods, the photochemistry and photophysics mechanism of isolated molecule reaction process can be investigated on a femtosecond time scale. The principles of TRMS and TRPEI are introduced here in detail. On the basis of substantial research achievements in our group, the applications of TRMS and TRPEI are presented in the study of ultrafast internal conversion and intersystem crossing, wavepacket evolution dynamics at excited states of polyatomic molecules, energy transfer process of polyatomic molecules, ultrafast photodissociation dynamics and structural evolution dynamics of molecular excited states. In the study of ultrafast internal conversion and intersystem crossing, the methyl substituted benzene derivatives and benzene halides are discussed as typical molecular systems. In the study of wavepacket evolution dynamics at excited states of polyatomic molecules, the real-time visualization of the dynamic evolution of CS2 4d and 6s Rydberg wave packet components, the vibrational wave packet dynamics in electronically excited pyrimidine, the rotational wave packet revivals and field-free alignment in excited o-dichlorobenzene are reported. In order to discuss the energy transfer process of polyatomic molecules, the intramolecular vibrational energy redisctribution between different vibrational states in p-difluorobenzene in the S1 low-energy regime and the intramolecular energy transfer between different electronic states in excited cyclopentanone are presented. For the study of ultrafast photodissociation dynamics, the dissociation constants and dynamics of the A band and even higher Rydberg states are investigated for the iodine alkanes and iodine cycloalkanes. Structural evolution dynamics of molecular excited states is the main focus of our recent research. The structural evolution dynamics can be extracted from the coherent superposition preparation of quantum states and the observation of quantum beat phenomenon, by taking 2, 4-difluorophenol and o-fluorophenol as examples. Time-dependent photoelectron peaks originating from the planar and nonplanar geometries in the first excited state in 2, 4-difluorophenol exhibit the clear beats with similar periodicities but a phase shift of π rad, offering an unambiguous picture of the oscillating nuclear motion between the planar geometry and the nonplanar minimum. Also, the structural evolution dynamics in o-fluorophenol via the butterfly vibration between planar geometry and nonplanar minimum is mapped directly. Finally, the potential developments and further possible research work and future directions of these techniques and researches are prospected.

Perylene‐Containing Conjugated Microporous Polymers for Photocatalytic Hydrogen Evolution

Three perylene‐containing conjugated microporous polymers (PrCMPs) are synthesized via Suzuki–Miyaura cross‐coupling reaction from perylene with four polymerizable functional groups and a range of different substituted benzene derivatives. The pore property and bandgap of the resulting PrCMPs can be tuned by changing the comonomer of benzene with different substituted groups and positions. The photocatalytic performances of the polymers are highly dependent on the surface area, geometry, and bandgap of the PrCMPs. It was found that the 1,2,4,5‐linked polymer of PrCMP‐3 shows the highest hydrogen evolution rate (HER) of 12.1 µmol h−1 under UV–vis light irradiation among the three polymers because of its high surface area, broad light absorption, and suitable bandgap. PrCMP‐3 also exhibits good photocatalytic stability for prolonged hydrogen production reaction. This result demonstrates that the crucial role of the linkage geometry offers a general principle for the rational design of conjugated microporous polymer photocatalysts. image

Sulfones in heterocyclic synthesis: advances in the chemistry of phenyl sulfonylacetophenone

The present review provides a survey on the structural features, synthetic methodologies, and reactions of phenyl sulfonylacetophenone, considered to be one of the most important synthons in the field of synthetic organic chemistry. β-Ketosulfone is an active C–H acid which has been widely used as a nucleophile in many organic transformations. It has been used for synthesis of five- and six-membered ring systems containing one or two heteroatoms. In addition, it has been used as a starting material for synthesis of fused heterocycles, cyclopropane, cyclopentene, and cyclohexanone derivatives. β-Ketosulfone has been used for synthesis of γ- and δ-ketosulfones, 1,4-diketones, amides, ethers, and substituted benzene derivatives due to its high synthetic importance. It is a reactive intermediate in electrophilic reactions such as halogenation, alkylation, arylation, heteroarylation, and coupling reactions, and is involved in other types of reaction such as Diels–Alder condensation with aldehydes and desulfonylation. The mechanistic pathways of these reactions and their important synthetic applications are discussed herein.