Adsorptive avidity of Prussian blue polypyrrole nanocomposite for elimination of water contaminants: a case study of malachite green and isoniazid.

Persistent water contaminants include a variety of substances that evade natural cleaning processes posing severe risks to ecosystems. Their adsorptive elimination is a key approach to safer attenuation. Herein we present the design and development of Prussian blue incorporated polypyrrole (PPY/PB) hybrid nanocomposite as a high-performance adsorbent for the elimination of malachite green (M.G.), isoniazid (INH) and 4-nitrophenol (4-NP) water contaminants. The nanocomposite synthesis was favored by strong dopant-polymer interactions, leading to a PPY/PB material with enhanced electro-active surface area compared to pristine PPY. The structure-activity response of the nanocomposite for the adsorption of target contaminants was unveiled by evaluating its maximum adsorption capacities under environmentally viable conditions. In-depth analysis and optimization of adsorption influencing factors (pH, temperature, and adsorbent dose) were performed. Using equilibrium studies, kinetic model fitting, aided with FTIR analysis, a multi-step mechanism for the adsorption of target contaminants on the nanocomposite was proposed. Furthermore, the PPY/PB nanocomposite also acts as a catalyst, enabling contaminant elimination following a synergistic scheme that was demonstrated using 4-NP contaminant. The synergetic adsorption and catalytic degradation of 4-NP using PPY/PB as adsorbent and catalyst was demonstrated in the presence of NaBH4 as a reducing agent in absence of light. In summary, this work highlights the targeted design of adsorbent, its optimization for adsorptive avidity, and the synergistic role of adsorption trapping in the catalytic degradation of persistent contaminants.

Visible-Light-Mediated Synthesis of Thioesters Using Thiocarboxylic Acid as the Dual Reagent.

We have developed a visible-light-driven method for thioester synthesis that relies on the unique dual role of thiobenzoic acids as one-electron reducing agents and reactants leading to the formation of sulfur radical species. This synthetic process offers a wide scope, accommodating various thioacid and thiol substrates without the need for a photocatalyst.

Visible-Light-Mediated Synthesis of N-Acyl-N,O-hemiacetals from Terminal Alkynes: Access to N,N-, N,S-, and N,O-Acetals.

A mild electron donor-acceptor complex-mediated approach for the synthesis of N-acyl-N,O-hemiacetals has been reported. The key feature of this protocol is that it allows for direct access to electrophilic N-acylimines at room temperature without prefunctionalization of the hydroxyl group. The in situ generated N-acylimine can react with different nucleophiles, viz., alcohols, thiols, and nitriles, to afford a diverse range of scaffolds such as N,O-, N,S-, and N,N-acetals.

Photoredox-Promoted Selective Synthesis of C-5 Thiolated 2-Aminothiazoles from Terminal Alkynes.

A mild photoredox approach enabling the first one-step synthesis of thiolated 2-aminothiazoles has been reported. Notably, the incorporation of thio group on electron-rich heteroarenes such as aminothiazoles via conventional nucleophilic aromatic substitution (SNAr) presents a significant challenge owing to polarity mismatch. Herein, we present a remarkable site-selective installation of thio group at the C-5 position of the electron-rich aminothiazole skeleton and successfully used them for the postfunctionalization of drugs and natural products.

Photoredox Catalyzed Thioformylation of Terminal Alkynes Using Nitromethane as a Formyl Source.

A photoredox thioformylation of terminal alkynes using nitromethane as a formyl anion equivalent, thereby leading to the synthesis of (E)-1,2-difunctionalized acrylaldehyde, has been described. The current strategy introduces an adaptable aldehyde function across an alkyne and offers a new route to synthesizing α-alkyl/aryl aldehydes.

Synthesis of 1,2-oxazetidines with a free -NH group via photoredox catalysis.

A photoredox approach enabling one-step synthesis of oxazetidines with a free -NH group via the combined use of alkyne, thiophenol, and azide has been reported. The synthesized oxazetidine with the free -NH group was stable enough for various late-stage transformations such as methylation, acetylation, tosylation, and ring-opening reaction to afford synthetically useful α-aminoketones.

Visible-Light-Promoted Oxidative Annulation of Naphthols and Alkynes: Synthesis of Functionalized Naphthofurans.

A visible-light-mediated site-selective oxidative annulation of naphthols with alkynes for the synthesis of functionalized naphthofurans has been developed. The reaction relies on the in situ formation of an electron donor acceptor pair between phenylacetylene and thiophenol as the light-absorbing system to obviate the requirement of an added photocatalyst. The protocol facilitates the transformation of 1-naphthol and 2-naphthol as well as 1,4-naphthoquinone into a wide variety of highly functionalized naphthofurans.

Organoselenium Compounds as Acetylcholinesterase Inhibitors: Evidence and Mechanism of Mixed Inhibition.

Acetylcholinesterase (AChE) inhibitors are actively used for the effective treatment of Alzheimer's disease. In recent years, the neuroprotective effects of organoselenium compounds such as ebselen and diselenides on the AChE activity have been investigated as potential therapeutic agents. In this work, we have carried out systematic kinetic and intrinsic fluorescence assays in combination with docking and molecular dynamics (MD) simulations to elucidate the molecular mechanism of the mixed inhibition of AChE by ebselen and diphenyl diselenide (DPDSe) molecules. Our MD simulations demonstrate significant heterogeneity in the binding modes and allosteric hotspots for DPDSe on AChE due to non-specific interactions. We have further identified that both ebselen and DPDSe can strongly bind around the peripheral anionic site (PAS), leading to non-competitive inhibition similar to other PAS-binding inhibitors. We also illustrate the entry of the DPDSe molecule into the gorge through a "side door", which offers an alternate entry point for AChE inhibitors as compared to the usual substrate entry point of the gorge. Together with results from experiments, these simulations provide mechanistic insights into the mixed type of inhibition for AChE using DPDSe as a promising inhibitor for AChE.

Photooxidation Coupled Kabachnik-Fields and Bigenelli reactions for Direct Conversion of Benzyl alcohols to α-Amino Phosphonates and Dihydropyrimidones.

A tandem one-pot solvent free approach for the direct conversion of benzyl alcohols to α-amino phosphonates and dihydropyrimidones is reported. The method relies on a metal free photo-oxidation of benzyl alcohols to benzaldehydes under UV irradiation using ammonium perchlorate followed by Kabachnik-Fields and Biginelli reactions. The reaction conditions are moderate and metal free with good substrate scope. The control experiments were performed to investigate the role of the ammonium perchlorate and molecular oxygen as oxidants. The quenching experiments in the presence of TEMPO and other radical quenchers suggest radical based mechanism.