Ammonia Synthesis on Ternary LaSi‐based Electrides: Tuning the Catalytic Mechanism by the Third Metal

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Ammonia Synthesis on Ternary LaSi-based Electrides: Tuning the Catalytic Mechanism by the Third Metal

La−TM−Si electrides catalysts for ammonia synthesis were compared and different catalytic mechanisms were shown for LaFe/CoSi and LaMnSi. A dual-site relay catalytic mechanism was demonstrated for LaCoSi and LaFeSi, breaking the scaling relations. In contrast, all the elementary steps were confined to Mn sites on LaMnSi, which resulted in inferior catalytic activity.


Abstract

Intermetallic electrides have recently drawn considerable attention due to their unique electronic structure and high catalytic performance for the activation of inert chemical bonds under mild conditions. However, the relationship between electride (anionic) electron abundance and catalytic performance is undefined; the key deciding factor for the performance of intermetallic electride catalysts remains to be addressed. Here, the secret behind electride catalysts La−TM−Si (TM=Co, Fe and Mn) with the same crystal structure but different anionic electrons was studied. Unexpectedly, LaCoSi with the least anionic electrons showed the best catalytic activity. The experiments and first-principles calculations showed that the electride anions promote the N2 dissociation which alters the rate-determining step (RDS) for ammonia synthesis on the studied electrides. Different reaction mechanisms were found for La−TM−Si (TM=Fe, Co) and LaMnSi. A dual-site module was revealed for LaCoSi and LaFeSi, in which transition metals were available for the N2 dissociation and La accelerates the NH x formation, respectively, breaking the Sabatier scaling relation. For LaMnSi, which is the most efficient for the N2 activation, the activity for ammonia synthesis is limited and confined by the scaling relations. The findings provide new insight into the working mechanism of intermetallic electrides.

Rhodium‐Catalysed Selective C−H Allylation of 1H‐Indazoles with Vinylethylene Carbonate: Easily Introducing Allylic Alcohol

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Rhodium-Catalysed Selective C−H Allylation of 1H-Indazoles with Vinylethylene Carbonate: Easily Introducing Allylic Alcohol

An efficient rhodium(III)-catalyzed C−H bond activation/allylation reaction of 3-aryl-1H-indazoles with easily available vinylethylene carbonate has been reported. A series of allyl alcohol substituted 3-aryl-1H-indazoles were obtained.


Abstract

An efficient rhodium(III)-catalysed C−H activation of 3-aryl-1-H-indazoles with easily available vinylethylene carbonate has been reported. A series of allyl alcohol substituted 3-aryl-1-H-indazoles were obtained with broad functional groups tolerance and favourable stereoselectivity. Notably, C−H and C−O bonds were selectively activated in “one pot” manner, releasing CO2 as the sole by-product and avoiding external oxidant. This protocol provides a powerful approach for the post stage C−H allylation of indazole-based substrates.

Electrochemical C7‐Indole Alkenylation via Rhodium Catalysis

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Electrochemical C7-Indole Alkenylation via Rhodium Catalysis

The merger of rhodium catalysis and electrochemical synthesis enabled the exclusive access to the C7−H electro-alkenylation of indoles.


Abstract

Indole derivatives are fundamental structural units in many bioactive compounds and molecular materials. The site-selective C7-functionalization of these moieties has been proven to be extremely challenging due to the inherent reactivity of the C2- and C3-positions. Herein, we report the first electro-C7-alkenylation of indoles. This novel and sustainable methodology provides highly exclusive access to the C7-position devoid of often toxic and expensive chemical oxidants. Moreover, an array of substrates was successfully alkenylated at the C7-position, and versatile product diversification was achieved.

Structural Modification of the Natural Product Valerenic Acid Tunes RXR Homodimer Agonism

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Structural Modification of the Natural Product Valerenic Acid Tunes RXR Homodimer Agonism

Valerenic acid is an RXR agonist with unique subtype and homodimer preference. We have studied the impact of structural modification of the natural product on RXR modulation and identified an analogue exhibiting enhanced and selective RXR homodimer activation.


Abstract

Retinoid X receptors (RXR) are ligand-sensing transcription factors with a unique role in nuclear receptor signaling as universal heterodimer partners. RXR modulation holds potential in cancer, neurodegeneration and metabolic diseases but adverse effects of RXR activation and lack of selective modulators prevent further exploration as therapeutic target. The natural product valerenic acid has been discovered as RXR agonist with unprecedented preference for RXR subtype and homodimer activation. To capture structural determinants of this activity profile and identify potential for optimization, we have studied effects of structural modification of the natural product on RXR modulation and identified an analogue with enhanced RXR homodimer agonism.

Synthesis and Electrochemical Investigation of Phosphine Substituted Diiron Phosphadithiolate Complexes

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Synthesis and Electrochemical Investigation of Phosphine Substituted Diiron Phosphadithiolate Complexes

Six novel phosphine substituted [FeFe] hydrogenase models with phosphinate in the bridgehead were synthesized and investigated by FTIR spectroscopy and cyclic voltammetry (CV). These ligand exchange reactions occur at milder conditions compared to literature procedures, resulting in a ligand-specific main product in all cases. Additionally, reflux conditions only influenced the complexes with bidentate ligands.


Abstract

This work reports on ligand exchange reactions between a [FeFe] hydrogenase model containing the higher homologue (PhosDT) and phosphines selected to cover a variety of electronic properties and possible coordination modes. Additionally, the amount of the phosphines and the reaction temperature were varied to study the formation of complexes with multiple phosphines or altered binding modes. Due to steric effects caused by the position of the bridgehead, the phosphines bind preferentially at the more accessible iron centre on the phosphinate averted side. While all ligand exchanges resulted in a ligand-specific main product at room temperature, reflux conditions induced decomposition in case of PhosDT-(κ2-dppe) and PhosDT-(κ2-dppv) and a change in the binding mode for the dppm containing complex. Moreover, we highlight two novel iron complexes obtained as side products of the reactions with dppe and dppv, while in case of dppm an additional model with two bridging phosphine ligands was generated. Finally, the six novel phosphine substituted PhosDT models were electrochemically investigated, revealing a cathodic shift compared to the starting material due to the increased electron density at the iron atoms. Moreover, the models with monodentate ligands exhibit a different CV pattern for the FeIFeI/FeIFe0 process than complexes with bidentate phosphines.

Three‐Dimensional Scaffolds for Light Emission

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Three-Dimensional Scaffolds for Light Emission

Here, we reported novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance.


Abstract

Organic fluorophores with highly efficient luminescence in both solution and solid states have attracted significant attention due to their ability to circumvent the limitations of aggregation-caused quenching and aggregation-induced emission type molecules. However, their development and wide-range applications are hampered by extremely complex synthetic methodologies and limited frameworks with dual-state emission (DSE) structural characteristics. In sharp contrast to the reported luminogens with big and planar π systems or highly conjugated and twisted structures, we discovered novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance. Our findings should open new avenues for designing DSE molecules with new frameworks, which will enable more successful development of dual-state emitters for their broad applications in the future.

Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’‐Carbonyldiimidazole Activated Fatty Acids

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Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’-Carbonyldiimidazole Activated Fatty Acids

A practical methodology for the synthesis of triacylglycerides utilizing fatty acids activated by 1,1’-carbonyldiimidazole (CDI) was developed to obtain protiated and deuterated medium chain triglyceride (MCT) oils as well as a synthetic plant oil mimic. New insights into the mechanism of the CDI activation were gained using deuterated substrates and via density-functional theory (DFT) calculations.


Abstract

Synthetic model triacylglyceride oils are important compounds for applications in pharmaceutical and food chemistry. Herein, a practical and highly efficient methodology for the synthesis of saturated and unsaturated triacylglycerides utilizing saturated and unsaturated fatty acids activated by 1,1’-carbonyldiimidazole (CDI) has been developed and applied in the synthesis of deuterated medium chain triglyceride (MCT) oil for studies of plant-based and diary food emulsions. The deuterium labelled compounds were used to gain new insight into the mechanism of the reaction, which was confirmed by density-functional theory (DFT) calculations.

Tandem Conversion of Fructose to Bio‐diketones Using a Multifunctional Pd‐POPs‐CF3SO3H Catalyst

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Tandem Conversion of Fructose to Bio-diketones Using a Multifunctional Pd-POPs-CF3SO3H Catalyst

A multifunctional heterogeneous Pd-POPs-CF3SO3H catalyst containing integrated acid and metal sites and anions was synthesized for tandem conversion of fructose to bio-diketones in good yield with an extraordinary TOF.


Abstract

Tandem conversion of biomass to value-added fine chemicals is a significant challenge. For instance, the production of fine chemicals from fructose involves conversion to 5-hydroxymethylfurfural (5-HMF), followed by another reaction and purification. Dual catalyst systems have been used in nearly every study on the tandem conversion of fructose to bio-diketones. Therefore, a sole multifunctional heterogeneous catalyst was developed in this study for the tandem conversion of fructose to bio-diketones, which has not been reported previously. Instrument corrosion and the separation or purification of 5-HMF were avoided using the multifunctional heterogeneous catalyst, which contained integrated active sites of acid, metal, and anions. The multifunctional CF3SO3H-functionalized porous-organic-polymers(POPs)-supported Pd catalyst (Pd-POPs-CF3SO3H) was prepared using a series of modifications. A bio-diketone yield of 51.0 % was achieved using Pd-POPs-CF3SO3H in the tandem conversion of fructose with an excellent TOF of 88.3 h−1 which is much more efficient than catalyst reported in literatures. Pd-POPs-CF3SO3H could be reused at least three times with stable performance. Control experiments and characterization results proved that the high specific surface area, hierarchical pore structure, abundance of CF3SO3 −1 anions, and proximity of Pd moieties and acid sites (“The closer the better” principle) led to the decent performance for bio-diketone.

Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage‐Gated Sodium Channels

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Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage-Gated Sodium Channels**

Trifunctional chemical probes derived from the potent shellfish poison, (+)-saxitoxin (STX), irreversibly inhibit wild-type voltage-gated sodium channels (NaVs). Saxitoxin derivatives decorated with a maleimide electrophile and either biotin, a fluorescent dye, or biorthogonal-reactive group were synthesized and evaluated using whole-cell, voltage-clamp electrophysiology.


Abstract

Voltage-gated sodium ion channels (NaVs) are integral membrane protein complexes responsible for electrical signal conduction in excitable cells. Methods that enable selective labeling of NaVs hold potential value for understanding how channel regulation and post-translational modification are influenced during development and in response to diseases and disorders of the nervous system. We have developed chemical reagents patterned after (+)-saxitoxin (STX) – a potent and reversible inhibitor of multiple NaV isoforms – and affixed with a reactive electrophile and either a biotin cofactor, fluorophore, or ‘click’ functional group for labeling wild-type channels. Our studies reveal enigmatic structural effects of the probes on the potency and efficiency of covalent protein modification. Among the compounds analyzed, a STX-maleimide-coumarin derivative is most effective at irreversibly blocking Na+ conductance when applied to recombinant NaVs and endogenous channels expressed in hippocampal neurons. Mechanistic analysis supports the conclusion that high-affinity toxin binding is a prerequisite for covalent protein modification. Results from these studies are guiding the development of next-generation tool compounds for selective modification of NaVs expressed in the plasma membranes of cells.

Recent Efforts in Identification of Privileged Scaffolds as Antiviral Agents

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Recent Efforts in Identification of Privileged Scaffolds as Antiviral Agents


Abstract

Viral infections are the most important health concern nowadays to mankind, which is unexpectedly increasing the health complications and fatality rate worldwide. The recent viral infection outbreak developed a pressing need for small molecules that can be quickly deployed for the control/treatment of re-emerging or new emerging viral infections. Numerous viruses, including the human immunodeficiency virus (HIV), hepatitis, influenza, SARS-CoV-1, SARS-CoV-2, and others, are still challenging due to emerging resistance to known drugs. Therefore, there is always a need to search for new antiviral small molecules that can combat viral infection with new modes of action. This review highlighted recent progress in developing new antiviral molecules based on natural product-inspired scaffolds. Herein, the structure-activity relationship of the FDA-approved drugs along with the molecular docking studies of selected compounds have been discussed against several target proteins. The findings of new small molecules as neuraminidase inhibitors, other than known drug scaffolds, Anti-HIV and SARS-CoV are incorporated in this review paper.