Sulfonyl vs. carbonyl group: which is the more electron-withdrawing?

Unusual Regio- and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate

A dearomative oxidation of pyrroles to Δ3-pyrrol-2-ones is described, which employs a sulfoxide as oxidant, in conjunction with a carboxylic acid anhydride and a Brønsted acid additive. 3-substituted pyrroles undergo regioselective oxidation to give the product isomer in which oxygen has been introduced at the more hindered position. Regioselectivity is rationalized by a proposed mechanism that proceeds by initial thianthrenium introduction at the less-hindered pyrrole α-position, followed by distal attack of an oxygen nucleophile and subsequent elimination of thianthrene. The same reaction conditions are also able to effect a chemoselective oxidation of indoles to indolin-3-ones and additionally of indolin-3-ones to 2-hydroxyindolin-3-ones. Here again, the regio- and chemoselectivities are rationalized through the intermediacy of a thianthrenium salt.

Synthesis of 1-Azatriene Complexes of Tungsten: Metal-Promoted Ring-Opening of Dihydropyridine

For nearly a century, chemists have explored how transition-metal complexes can affect the physical and chemical properties of linear conjugated polyenes and heteropolyenes. While much has been written about higher hapticity complexes (η4-η6), less is known about the chemistry of their η2 analogues. Herein, we describe a general method for synthesizing 5,6-η2-(1-azatriene) tungsten complexes via a 6π-azaelectrocyclic dihydropyridine ring-opening that is promoted by the π-basic nature of {WTp(NO)(PMe3)}. This study includes detailed spectroscopic and crystallographic data for the η2-dihydropyridine and η2-1-azatriene complexes, both of which were prepared as single regio- and stereoisomers.

Annulation reactions of electrophilic benzannulated heterocycles towards heteroacenes

The current review describes different annulation strategies reported with electrophilic benzannulated heterocycles for accessing heteroacenes. For the past two decades, the chemistry of electrophilic benzannulated heterocycles was extensively investigated, and several dipolar cycloadditions, metal and organo-catalyzed transformations were introduced for the generation of fused heterocycles. In this review, we have collected all the reports where the annulation of electrophilic benzannulated heterocycles results in a fully aromatic system, viz. heteroacenes with tri-, tetra-, and pentacyclic rings. We reviewed every paper on the synthesis of fused heterocycles that was accessible and categorized the review into several parts based on the electrophilic benzannulated heterocycle used in the heteroacene synthesis such as electrophilic indole, electrophilic benzothiophene, and so forth. The generality and mechanistic postulates of each methodology are highlighted. In addition, we have also tried to feature the advantages or shortcomings of each method and have mentioned the possible applications of these methodologies for accessing heteroacenes for material applications.

N-Sulfonyl-1,2,3,4-tetrahydroisoquinoline Derivatives: Synthesis, Antimicrobial Evaluations, and Theoretical Insights

Microbial contamination remains a significant economic challenge in the food industry, emphasizing the need for innovative antimicrobial solutions. In this study, we synthesized N-sulfonyl-1,2,3,4-tetrahydroisoquinolines (NSTHIQ) derivatives using an environmentally friendly Preyssler heteropolyacid catalyst, obtaining moderate to high yields (35-91 %) under mild conditions. Two derivatives (5 and 6) exhibited significant antifungal properties against various fungal species, including Aspergillus spp, Penicillium spp, and Botrytis cinerea. ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) analysis revealed the absence of hepatic toxicity in all compounds, making derivatives 2, 3, 4, and 5 potential candidates for further development. However, derivatives 6 and 7 exhibited immunotoxicity. In support of our experimental findings, reactivity indices were computed using Density Functional Theory principles, deriving valuable insights into the chemical properties of these derivatives. This study underscores the potential of NSTHIQ compounds as potent antifungal agents, coupled with the importance of employing environmentally friendly catalysts in drug discovery.

Linking Redox Characteristics to Dissolved Organic Matter Derived from Different Biowaste Composts: A Theoretical Modeling Approach Based on FT-ICR MS Analysis

Compost dissolved organic matter (DOM) is a complex mixture of redox-active organic molecules that impact various biogeochemical processes in soil environments. However, the impact of chemical complexity (heterogeneity and chemodiversity) on the electron accepting capacity (EAC) and electron donating capacity (EDC) of DOM molecules remains unclear, which hinders our ability to predict their environmental behavior and redox properties. In this study, the applicability of Vienna Soil Organic Matter Modeler 2 (VSOMM2) to the composting system based on the FT-ICR MS data has been validated. A molecular modeling approach using VSOMM2 and Schrödinger software was developed to quantitatively assess the redox sites and molecular interactions of compost DOM. Compost DOM molecules are categorized into three distinct groups based on their heterogeneous origins. In addition, we have developed 18 molecular models of compost DOM based on the links of molecules to EAC/EDC. Finally, Ar-OH, quinone, Ar-SH, and Ar-NH2 were identified as the redox sites; noncovalent contacts, H bonds, salt bridges, and aromatic-H bonds might be significant electronic transmission channels of compost DOM. Our findings contribute to the development of precise regulatory methods for functional molecules within compost DOM, providing the fine standards for composts matching specific ecosystem service requirements.

Synthesis of N-alkoxycarbonyl Pyrroles from O-Substituted Carbamates: A Synthetically Enabling Pyrrole Protection Strategy

The condensation of readily available O-substituted carbamates with 2,5-dimethoxytetrahydrofuran gives N-alkoxycarbonyl pyrroles in a single step and in good yield. By this method, several common amine protecting groups can be introduced on the pyrrole nitrogen. With the exception of N-Boc, N-alkoxycarbonyl groups have seen only minimal use for protection of the pyrrole nitrogen to date. Here, we show that N-alkoxycarbonyl protection can endow pyrrole with distinct reactivity in comparison with N-sulfonyl protection, for example, in a pyrrole acylation protocol employing carboxylic acids with a sulfonic acid anhydride activator.

Next generation multimodal chromatography resins via an iterative mapping approach: Chemical diversity, high-throughput screening, and chromatographic modelling

Multimodal chromatography resins are becoming a key tool in the purification of biomolecules. The main objective of this research was the establishment of an iterative framework for the rapid development of new multimodal resins to provide novel selectivity for the future purification challenges. A large chemically diverse virtual library of 100 multimodal Capto™ MMC ligand analogues was created, and a broad array of chemical descriptors were calculated for each ligand in silico. Principal component analysis (PCA) was used to map the chemical diversity and guide selection of ligands for synthesis and coupling to the Capto ImpRes agarose base matrix. Twelve new ligands were prepared in two groups: 'group one' consist of L00-L07 and 'group two' consist of L08-L12. These ligands are diverse in the influence of varied secondary interactions such as hydrophobic interactions, H-bonding, etc. Additional resin prototypes were also prepared to look at the chromatographic impact of ligand density variation. High-throughput plate-based studies were performed for parallel resin screening for batch-binding of six model proteins at different chromatographic binding pH and sodium chloride concentration conditions. Principal component analysis of the binding data provided a chromatographic diversity map leading to the identification of ligands with improved binding. Further, the new ligands have improved separation resolution between a monoclonal antibody (mAb1) and product related impurities, a Fab fragment and high molecular weight (HMW) aggregates, using linear salt gradient elutions. To quantify the importance of secondary interactions, analysis of the retention factor of mAb1 on the ligands at various isocratic conditions lead to estimations of (a) the total number of water molecules and counter salt ions released during adsorption, and (b) hydrophobic contact area (HCA). The iterative mapping approach of chemical and chromatography diversity maps described in the paper proves to be a promising method for identifying new chromatography ligands for biopharmaceutical purification challenges.

Computer-Aided Discovery and Redesign for Respiratory Sensitization: A Tiered Mechanistic Model to Deliver Robust Performance Across a Diverse Chemical Space

Asthma is among the most common occupational diseases with considerable public health and economic costs. Chemicals that induce hypersensitivity in the airways can cause respiratory distress and comorbidities with respiratory infections such as COVID. Robust predictive models for this end point are still elusive due to the lack of an experimental benchmark and the over-reliance of existing in silico tools on structural alerts and structural (vs chemical) similarities. The Computer-Aided Discovery and REdesign (CADRE) platform is a proven strategy for providing robust computational predictions for hazard end points using a tiered hybrid system of expert rules, molecular simulations, and quantum mechanics calculations. The recently developed CADRE model for respiratory sensitization is based on a highly curated data set of structurally diverse chemicals with high-fidelity biological data. The model evaluates absorption kinetics in lung mucosa using Monte Carlo simulations, assigns reactive centers in a molecule and possible biotransformations via expert rules, and determines subsequent reactivity with cell proteins via quantum-mechanics calculations using a multi-tiered regression. The model affords an accuracy above 0.90, with a series of external validations based on literature data in the range of 0.88-0.95. The model is applicable to all low-molecular-weight organics and can inform not only chemical substitution but also chemical redesign to advance development of safer alternatives.

An Overview of NRF2-Activating Compounds Bearing α,β-Unsaturated Moiety and Their Antioxidant Effects

The surge of scientific interest in the discovery of Nuclear Factor Erythroid 2 (NFE2)-Related Factor 2 (NRF2)-activating molecules underscores the importance of NRF2 as a therapeutic target especially for oxidative stress. The chemical reactivity and biological activities of several bioactive compounds have been linked to the presence of α,β-unsaturated structural systems. The α,β-unsaturated carbonyl, sulfonyl and sulfinyl functional groups are reportedly the major α,β-unsaturated moieties involved in the activation of the NRF2 signaling pathway. The carbonyl, sulfonyl and sulfinyl groups are generally electron-withdrawing groups, and the presence of the α,β-unsaturated structure qualifies them as suitable electrophiles for Michael addition reaction with nucleophilic thiols of cysteine residues within the proximal negative regulator of NRF2, Kelch-like ECH-associated protein 1 (KEAP1). The physicochemical property such as good lipophilicity of these moieties is also an advantage because it ensures solubility and membrane permeability required for the activation of the cytosolic NRF2/KEAP1 system. This review provides an overview of the reaction mechanism of α,β-unsaturated moiety-bearing compounds with the NRF2/KEAP1 complex, their pharmacological properties, structural activity-relationship and their effect on antioxidant and anti-inflammatory responses. As the first of its kind, this review article offers collective and comprehensive information on NRF2-activators containing α,β-unsaturated moiety with the aim of broadening their therapeutic prospects in a wide range of oxidative stress-related diseases.

Chlorination of para-substituted phenols: Formation of α, β-unsaturated C4-dialdehydes and C4-dicarboxylic acids

Despite the widespread occurrence of phenols in anthropogenic and natural compounds, their fate in reactions with hypochlorous acid (HOCl), one of the most common water treatment disinfectants, remains incompletely understood. To close this knowledge gap, this study investigated the formation of disinfection by-products (DBPs) in the reaction of free chlorine with seven para-substituted phenols. Based on the chemical structures of the DBPs and the reaction mechanisms leading to their formation, the DBPs were categorized into four groups: chlorophenols, coupling products, substituent reaction products, and ring cleavage products. In contrast to previous studies that investigated the formation of early-stage chlorophenols, the primary focus of this study was on the elucidation of novel ring cleavage products, in particular α, β-unsaturated C₄-dialdehydes, and C₄-dicarboxylic acids, which, for the first time, were identified and quantified in this study. The molar yields of 2-butene-1,4-dial (BDA), one of the identified α, β-unsaturated C₄-dialdehydes, varied among the different phenolic compounds, reaching a maximum value of 10.4% for bisphenol S. Molar yields of 2-chloromaleic acid (Cl-MA), one of the identified C₄-dicarboxylic acids, reached a maximum value of 30.5% for 4-hydroxy-phenylacetic acid under given conditions. 2,4,6-trichlorophenol (TCP) was shown to be an important intermediate of the parent phenols and the C₄-ring cleavage products. Based on the temporal trends of α, β-unsaturated C₄-dialdehydes and C₄-dicarboxylic acids, their formation is likely attributable to two separate ring cleavage pathways. Based on the obtained results, an overall transformation pathway for the reaction of para-substituted phenols with free chlorine leading to the formation of novel C₄ ring cleavage products was proposed.

The effect of various compounds on the COVID mechanisms, from chemical to molecular aspects

The novel coronavirus that caused COVID-19 pandemic is SARS-CoV-2. Although various vaccines are currently being used to prevent the disease's severe consequences, there is still a need for medications for those who become infected. The SARS-CoV-2 has a variety of proteins that have been studied extensively since the virus's advent. In this review article, we looked at chemical to molecular aspects of the various structures studied that have pharmaceutical activity and attempted to find a link between drug activity and compound structure. For example, designing of the compounds which bind to the allosteric site and modify hydrogen bonds or the salt bridges can disrupt SARS-CoV2 RBD–ACE2 complex. It seems that quaternary ammonium moiety and quinolin-1-ium structure could act as a negative allosteric modulator to reduce the tendency between spike-ACE2. Pharmaceutical structures with amino heads and hydrophobic tails can block envelope protein to prevent making mature SARS-CoV-2. Also, structures based on naphthalene pharmacophores or isosteres can form a strong bond with the PLpro and form a π-π and the Mpro's active site can be occupied by octapeptide compounds or linear compounds with a similar fitting ability to octapeptide compounds. And for protein RdRp, it is critical to consider pH and pKa so that pKa regulation of compounds to comply with patients is very effective, thus, the presence of tetrazole, phenylpyrazole groups, and analogs of pyrophosphate in the designed drugs increase the likelihood of the RdRp active site inhibition. Finally, it can be deduced that designing hybrid drug molecules along with considering the aforementioned characteristics would be a suitable approach for developing medicines in order to accurate targeting and complete inhibition this virus.

Hyperbaric reactions in organic synthesis. Progress from 2006 to 2020

This comprehensive review summarizes the published literature data concerning above 1 kbar reactions for the purposes of preparative organic synthesis (more then 50 mg of the initial substance) from 2006...

Straightforward Synthesis of Indenes by Gold-Catalyzed Intramolecular Hydroalkylation of Ynamides

An original and straightforward entry to polysubstituted indenes from readily available ynamides is reported. Upon reaction with a N-heterocyclic carbene-gold complex under mild conditions, activated keteniminium ions are generated whose unique electrophilicity triggers a [1,5]-hydride shift and a subsequent cyclization. The presence of an endocyclic enamide in the densely functionalized resulting indenes was shown to be especially useful and versatile, offering a range of opportunities for their further postfunctionalization.

How electrophilic are 3-nitroindoles? Mechanistic investigations and application to a reagentless (4+2) cycloaddition

The electrophilicity of 4 different 3-nitroindole derivatives has been evaluated by Mayr's linear free energy relationship (log k(20 °C) = s_N(E + N)) and reveals unexpected values for aromatic compounds, in the nitrostyrene range. 3-Nitroindoles are sufficiently electrophilic to interact with a common diene namely the Danishefsky's diene at room temperature, in the absence of any activator, to furnish smoothly the dearomatized (4+2) cycloadducts in good yields.

Highly Selective and Catalytic C-N Bond Cleavage of Tertiary Sulfonamides: Scope and Mechanistic Insight

A highly chemoselective C-N bond cleavage reaction of p-methoxybenzyl- (PMB), 3,4-dimethoxybenzyl- (DMB), or cinnamyl-substituted tertiary sulfonamides in the presence of catalytic Bi(OTf)₃ is presented. A wide range of sulfonamide substrates smoothly furnished the corresponding C-N bond cleavage products in good to excellent yields. Great efforts have been made to obtain insights into the reaction mechanism based on a series of control experiments and mass spectroscopy.

Fabrication of a Nanoporous Silica Hydrogel by Cross-Linking of SiO2-H3BO3-Hexadecyltrimethoxysilane for Excellent Adsorption of Azo Dyes from Wastewater

This study reports a novel cross-linking approach to fabricate the hydrothermally neutralized silica hydrogel of SiO₂-H₃BO₃-hexadecyltrimethoxysilane by grafting alkylsilane groups onto the nanoporous silica. The synthesized silica hydrogel possessed a large specific surface area of 51.3 m²g^-1 and showed excellent dye adsorption capability of cationic dyes in neutral (pH 7) and alkaline (pH 9) medium from wastewater. The colloidal electrokinetic potential analysis revealed that the outstanding adsorption efficiency of cationic dyes over anionic dyes strongly relies on the surface charge of the hydrogels. Moreover, the hydrophobic interactions between the dye molecules and the hydrogels were studied, and it was found that the dye adsorption performance can be tuned by altering the concentration of hydrophobic reagents of the hydrogel. The dye adsorption mechanism was established, and the kinetic study suggested that the adsorption is a pseudo-second-order reaction. Adsorption isotherms at various equilibrium conditions fitted well with the Langmuir isotherm. Therefore, this strongly supports the promising and practical application of the prepared silica hydrogel. The recyclability of the hydrogel was studied, and it showed 90% adsorption efficiency by the regenerated gel up to 6 cycles, which has a high potential in wastewater treatment.

Reactivity of 3-nitroindoles with electron-rich species

The indol(in)e building block is one of the "privileged-structures" for the pharmaceutical industry since this fragment plays a central role in drug discovery. While the electron-rich character of the indole motif has been investigated for decades, exploiting the electrophilic reactivity of 3-nitroindole derivatives has recently been put at the heart of a wide range of new, albeit challenging, chemical reactions. In particular, dearomatization processes have considerably enriched the scope of C2[double bond, length as m-dash]C3 functionalizations of these scaffolds. This feature article showcases this remarkable electrophilic reactivity of 3-nitroindoles with electron-rich species and highlights their value in generating diversely substituted indol(in)es. This compilation underlines how these heteroaromatic templates have gradually become model substrates for electron-poor aromatic compounds in dearomatization strategies.

Dearomatization of 3-cyanoindoles by (3 + 2) cycloaddition: from batch to flow chemistry

1,3-Dipolar dearomatizing cycloadditions between a non-stabilized azomethine ylide and 3-cyanoindoles or benzofuran afford the corresponding 3D-heterocycles bearing a quaternary carbon centre at the ring junction. While 6 equivalents of ylide precursor 1 are required for full conversion in a classical flask, working under flow conditions limits the excess (3 equiv., tR = 1 min) and leads to a cleaner process, affording cycloadducts that are easier to isolate.

Electrostatic repulsion-controlled regioselectivity in nitrene-mediated allylic C–H amidations

The difference of repulsive electrostatic interactions between nitrene N and allyl carbon atoms is the dominant factor affecting the regioselectivity in metal nitrenoid-catalyzed allylic C–H amidations.

Azanorbornadienes as Thiol-Reactive Cleavable Linkers

Azanorbornadienes (ZNDs), prepared from pyrroles, undergo Michael reaction with thiols followed by retro-Diels-Alder (rDA) cleavage to release the starting pyrrole and a thiomaleate. Somewhat less reactive in this regard than furan-derived oxanorbornadienes, ZNDs have an additional point of variability at the pyrrole nitrogen center. Sulfonylated ZNDs were far more stable toward rDA cleavage than acylated analogues. tert-Butoxycarbonyl examples were much less reactive with thiols, rendering the rDA step slower than the initial conjugate addition.

Synthesis of Tetrasubstituted Thiophenes via Direct Metalation

Thiophene moiety can be derivatized by various synthetic procedures. The most convenient method seems to be derivatization via direct metalation, but synthesis of polysubstituted thiophenes bearing reactive groups is difficult because of high reactivity of organometallic reagents. This work reports the preparation of complex heterocyclic compounds using direct metalation of thiophenes with various reagents (Knochel-Hauser bases, LDA) as an efficient synthetic tool.

Synthesis of Annulated Indolines by Reductive Fischer Indolization

Cyclic β-oxoesters and arylhydrazine derivatives were converted at ambient temperature under modified Fischer indolization conditions to furnish annulated indolines with quaternary bridgehead carbon center. Reaction conditions were Brønsted acidic (with CF₃ CO₂ H), but also reductive (with Et₃ SiH). The latter reduced intermediate iminium ions under formation of the 2,3-dihydroindole product constitutions. Racemic products (13 examples) were obtained as single diastereoisomers with relative cis-configuration, which was proved in two cases by single-crystal X-ray structure analysis. Conversion of 4-bromo-1-indanone-2-carboxylate and 4-bromophenylhydrazine gave indeno[1,2-b]indolines with either 1-bromo, 8-bromo, or 1,8-dibromo substitution, which were further diversified by Suzuki coupling reactions with several arylboronic acids (nine examples).

Phosphine-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans and nitrobenzothiophenes with allenoates

An efficient Ph₂PMe-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, and 3-nitrobenzothiophenes with allenoates is reported.

Synthesis and radiofluorination of novel fluoren-9-one based derivatives for the imaging of α7 nicotinic acetylcholine receptor with PET

By structure-activity relationship studies on the tilorone scaffold, the 'one armed' substituted dibenzothiophenes and the fluoren-9-ones were identified as the most potential α₇ nAChR ligands. While the suitability of dibenzothiophene derivatives as PET tracers is recognized, the potential of fluoren-9-ones is insufficiently investigated. We herein report on a series of fluoren-9-one based derivatives targeting α₇ nAChR with compounds 8a and 8c possessing the highest affinity and selectivity. Accordingly, with [¹⁸F]8a and [¹⁸F]8c we designed and initially evaluated the first fluoren-9-one derived α₇ nAChR selective PET ligands. A future application of these radioligands is facilitated by the herein presented successful implementation of fully automated radiosynthesis.

Diastereo- and Enantioselective Dearomative [3 + 2] Cycloaddition Reaction of 2-Nitrobenzofurans with 3-Isothiocyanato Oxindoles

Enantioselective dearomative [3 + 2] cycloaddition reaction of 2-nitrobenzofurans with 3-isothiocyanato oxindoles was developed. The reaction employs a chiral bis(oxazoline)/Zn(OTf)₂ catalyst, allowing a practical, straightforward access to structurally diverse spirooxindoles containing a 2,3-dihydrobenzofuran motif and three contiguous stereocenters with excellent diastereo- and enantioselectivities. The synthetic potentials of the method have been demonstrated by the scale-up experiment and transformations of the products. The preliminary mechanism was investigated with experimental observations, nonlinear effects studies, and MS experiments.

The effect of the intramolecular C–H⋯O interactions on the conformational preferences of bis-arylsulfones – 5-HT6 receptor antagonists and beyond

The development of compounds with enhanced activity and selectivity by a conserved spatial orientation of the pharmacophore elements has a long history in medicinal chemistry. Rigidified compounds are an example of this concept. However, the intramolecular interactions were seldom used as a basis for conformational restraints. Here, we show the weak intramolecular interactions that contribute to the relatively well-conserved geometry of N1-arylsulfonyl indole derivatives. The structure analysis along with quantum mechanics calculations revealed a crucial impact of the sulfonyl group on the compound geometry. The weak intramolecular C–H⋯O interaction stabilizes the mutual "facing" orientation of two aromatic fragments. These findings extend the pharmacological interpretation of the sulfonyl group role from the double hydrogen bond acceptor to the conformational scaffold based on intramolecular forces. This feature has, to date, been omitted in in silico drug discovery. Our results should increase the awareness of researchers to consider the conformational preference when designing new compounds or improving computational methods.

The impact of weak intramolecular C–H⋯O interactions on the conformational stability of bis-arylsulfones is discussed, suggesting different role of sulfonyl group in the ligand – 5HT₆ receptor interaction.

Photocatalytic Indole Diels-Alder Cycloadditions Mediated by Heterogeneous Platinum-Modified Titanium Dioxide

Indole alkaloids represent an important class of molecules, with many naturally occurring derivatives possessing significant biological activity. One area that requires further development in the synthesis of indole derivatives is the Diels-Alder reaction. In this work, we expand on our previously developed heterogeneous protocol for the [4+2] cycloaddition of indoles and electron-rich dienes mediated by platinum nanoparticles supported on titanium dioxide semiconductor particles (Pt(0.2%)@TiO₂) with visible-light irradiation. This reaction proceeds with broad scope and is more efficient per incident photon than the previous homogeneous method, and the catalyst can be easily recycled and reused.

Multiple Hydrogen-Bonding Bifunctional Thiourea-Catalyzed Asymmetric Dearomative [4 + 2] Annulation of 3-Nitroindoles: Highly Enantioselective Access to Hydrocarbazole Skeletons

A method for the enantioselective construction of hydrocarbazole skeletons through dearomative [4 + 2] annulation of 3-nitroindoles with Nazarov reagents is reported. The reactions use multiple hydrogen-bonding bifunctional thiourea as catalyst and are highly diastereo- and enantioselective (up to >20:1 dr and >99% ee). The protocol was demonstrated by preparative-scale experiment and the versatile conversion of the products. The multiple hydrogen-bonding in the catalyst plays a pivotal role in the reactivity and stereoselectivity.

Visible-light-induced oxidant and metal-free dehydrogenative cascade trifluoromethylation and oxidation of 1,6-enynes with water

Unprecedented light-induced oxidant and metal-free tandem radical cyclization–trifluoromethylation and dehydrogenative oxygenation of 1,6-enynes have been achieved using a photoredox catalyst, CF₃SO₂Na, and water as the oxygen source.

Generally, oxy-trifluoromethylation in olefins is achieved using oxidants and transition metal catalysts. However, labile olefins remain unexplored due to their incompatibility with harsh reaction conditions. Here, unprecedented light-induced oxidant and metal-free tandem radical cyclization–trifluoromethylation and dehydrogenative oxygenation of 1,6-enynes have been achieved using a photoredox catalyst, CF₃SO₂Na, and phenanthrene-9,10-dione (PQ), Langlois’ reagent (CF₃SO₂Na) and water as the oxygen source. This benign protocol allows for access to various CF₃-containing C₃-aryloyl/acylated benzofurans, benzothiophenes, and indoles. Moreover, the oxidized undesired products, which are inherently formed by the cleavage of the vinylic carbon and heteroatom bond, have been circumvented under oxidant free conditions. The mechanistic investigations by UV-visible and ESR spectroscopy, electrochemical studies, isotope labelling and density functional theory (DFT) suggest that light induced PQ produced a CF₃ radical from CF₃SO₂Na. The generated CF₃ radical adds to the alkene, followed by cyclization, to provide a vinylic radical that transfers an electron to PQ and generates a vinylic cation. Alternatively, electron transfer may occur from the CF₃-added alkene moiety, forming a carbocation, which would undergo cationic cyclization to generate a vinylic carbocation. The subsequent addition of water to the vinylic cation, followed by the elimination of hydrogen gas, led to the formation of trifluoromethylated C₃-aryloyl/acylated heterocycles.

Comparative evaluation of 11 in silico models for the prediction of small molecule mutagenicity: role of steric hindrance and electron-withdrawing groups

The goal of this investigation was to perform a comparative analysis on how accurately 11 routinely-used in silico programs correctly predicted the mutagenicity of test compounds that contained either bulky or electron-withdrawing substituents. To our knowledge this is the first study of its kind in the literature. Such substituents are common in many pharmaceutical agents so there is a significant need for reliable in silico programs to predict precisely whether they truly pose a risk for mutagenicity. The predictions from each program were compared to experimental data derived from the Ames II test, a rapid reverse mutagenicity assay with a high degree of agreement with the traditional Ames assay. Eleven in silico programs were evaluated and compared: Derek for Windows, Derek Nexus, Leadscope Model Applier (LSMA), LSMA featuring the in vitro microbial Escherichia coli-Salmonella typhimurium TA102 A-T Suite (LSMA+), TOPKAT, CAESAR, TEST, ChemSilico (±S9 suites), MC4PC and a novel DNA docking model. The presence of bulky or electron-withdrawing functional groups in the vicinity of a mutagenic toxicophore in the test compounds clearly affected the ability of each in silico model to predict non-mutagenicity correctly. This was because of an over reliance on the part of the programs to provide mutagenicity alerts when a particular toxicophore is present irrespective of the structural environment surrounding the toxicophore. From this investigation it can be concluded that these models provide a high degree of specificity (ranging from 71% to 100%) and are generally conservative in their predictions in terms of sensitivity (ranging from 5% t o 78%). These values are in general agreement with most other comparative studies in the literature. Interestingly, the DNA docking model was the most sensitive model evaluated, suggesting a potentially useful new mode of screening for mutagens. Another important finding was that the combination of a quantitative structure-activity relationship and an expert rules system appeared to offer little advantage in terms of sensitivity, despite of the requirement for such a screening paradigm under the ICH M7 regulatory guideline.

Addition of 4-(cyclohex-1-en-1-yl)morpholine on 3-nitroindole: an unprecedented dearomatizing process

Nucleophilic enamine2aadd spontaneously on nitroindole1to form a dearomatized formal ene adduct3a.

Bisphenol A and its analogs induce morphological and biochemical alterations in human peripheral blood mononuclear cells (in vitro study)

Few studies have addressed the cellular effects of bisphenol S (BPS) and bisphenol AF (BPAF) on cells, and no study has been conducted to analyze the mechanism of action of bisphenols in blood cells. In this study, the effect of bisphenol A (BPA), bisphenol F (BPF), BPS and BPAF on human peripheral blood mononuclear cells (PBMCs) was analyzed. It was shown that BPA, BPF and BPAF in particular, decreased cell viability, which was associated with depletion of intracellular ATP level and alterations in PBMCs size and granulation. Bisphenols enhanced ROS (including OH˙) formation, which led to damage to lipids and proteins in PBMCs. The most significant alterations in ROS level were induced by BPF, and particularly BPAF. Moreover, it was shown that BPAF most strongly provoked lipid peroxidation, while BPA and BPS caused the greatest damage to proteins. It may be concluded that BPA and its analogs were capable of inducing oxidative stress and damage in PBMCs in the concentrations ranging from 0.06 to 0.5 μM (0.02-0.1 μg/ml), which may be present in human blood as a result of environmental exposure. Although, most of bisphenols studied decreased cell viability, size and ATP level at higher concentrations, BPAF exhibited its cytotoxic potential at low concentrations ranging from 0.3 to 3 μM (0.1-1.0 μg/ml) that may correspond to concentrations in humans following occupational exposure.

Carboxymethylation of polysaccharides from Tremella fuciformis for antioxidant and moisture-preserving activities

The carboxymethylated polysaccharide (CATP), which derived from water-insoluble crude Tremella fuciformis polysaccharide (ATP), was prepared. And then the antioxidant and moisture-preserving activities of the samples were investigated. The results of chemical composition and FT-IR analysis showed the carboxymethylated modifications of polysaccharide were successful. The degree of substitution (DS) of four carboxymethylated derivatives were different with the molar of monochloroacetic acid. Their water solubility and biological activities were improved with the increase of DS. And moreover, a high antioxidant and moisture-preserving activities of CATPs was observed, so this derivative needs to be attention and studied in further. Results proved that the carboxymethylation could effectively enhance their potential biological properties of the polysaccharide.