Rapid Access to Divergent Fused Polycycles Via One-Pot A3 Coupling and Intramolecular Diels-Alder Reaction

Divergent nitrogen-containing fused polycyclic ring systems are constructed from simple starting materials via a one-pot aldehyde-alkyne-amine (A3) coupling and intramolecular Diels-Alder reaction. This domino reaction directly furnishes linear 5/5/5 and 5/5/6, or nonlinear 5/5/6/5, polycyclic rings containing an oxa-bridged fused 5/5 bicycle and a 1,6-enyne substructure. One-step derivation of the oxa-bridged 5/5 bicycle leads to a polyfunctionalized 5/5 bicycle with tetrahydrofuran fused back-to-back to pyrroline or a 6/5 bicycle with the hexahydro-1H-isoindole structure, while cycloisomerizing the enyne substructure adds an extra fused 5-membered ring to afford functionalized linear 5/5/5/5 or 5/5/5/5/5 fused ring systems from selected substrates. In addition, the one-pot product can be designed so that the alkyne moiety is hydroalkoxylated to form an additional heterocyle in a linear 5/5/5/6 or nonlinear 5/5/6/5/5 ring system. This diversity-oriented synthetic approach thus allows rapid access to an under-explored structural space for discovery of new biological or non-biological activities or functions.

Copper ions reinforced flexible carboxymethylcellulose/polyethyleneimine composite films with enhanced mechanical properties, UV-shielding performance, thermal stability, solvent resistance, and antibacterial activity

A composite film (CMC/PEI) consisting of anionic carboxymethylcellulose (CMC) and cationic polyethyleneimine (PEI) can be easily produced through the solution casting method using self-assembly based on electrostatic interaction and hydrogen bonding. Subsequently, the resulting CMC/PEI polyelectrolyte composite film with a network structure was crosslinked with divalent Cu2+ ions through ionic and coordination bonds, resulting in a strengthened Cu(II)@CMC/PEI film. The composite film was characterized based on its structural, surface, thermal, UV protection, antibacterial, and degradation aspects. The results demonstrated this film has impressive mechanical properties, remarkable solvent resistance, good antibacterial properties, and excellent UV-shielding performance by completely blocking ultraviolet light with wavelengths below 360 nm. These properties can be attributed to the presence of Cu2+ ions and PEI in the film. This work is valuable for the development of novel UV-shielding materials and should contribute to the design of carboxymethylcellulose composite films with desirable properties and exceptional performance.

Carboxymethyl cellulose nanocolloids anchored Pd(0) nanoparticles (CMC@Pd NPs): synthesis, characterization, and catalytic application in transfer hydrogenation

Herein, we report on the preparation of novel colloidal system based on carboxymethyl cellulose (CMC) and Pd nanoparticles (CMC@Pd NPs) via an ecofriendly auto-reduction process under mild conditions. In the first step, the follow-up of reduction and preparation of CMC anchored palladium nanoparticles (Pd NPs) in aqueous solution was carried out using UV-Vis spectroscopy. Thereafter, the monodispersed colloids were fully characterized by advanced analytical, structural, and morphological techniques. Based on Scherrer equation, the as-synthesized CMC@Pd NPs crystallite size was about 10.88 nm. Accordingly, the detailed microscopic study revealed CMC nanocolloids anchored uniform distribution of Pd NPs and the presence of CMC nanofilm as protective monolayer. To the best of our knowledge, the observed nanoscale properties are reported for the first time for CMC-M system. The performance of the as-synthesized CMC@Pd nanocolloids was first investigated in the reduction of 4-nitrophenol, as a model substrate, to 4-aminophenol using NaBH4 as a hydrogen source. Moreover, the catalytic reduction of various nitroarenes bearing electron withdrawing or donating substituents was carried out and monitored by UV-Vis spectroscopy. The chemo- and regioselectivity of the catalytic reduction in presence of CMC@Pd NPs were also studied. Consequently, the prepared CMC@Pd nanocolloids exhibit remarkable activity, good heterogeneity, and higher reusability and stability for the catalytic reduction reaction under mild conditions.

Carboxymethyl cellulose nanocomposite beads as super-efficient catalyst for the reduction of organic and inorganic pollutants

Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) nanocomposite beads were prepared by facile, simple and environmentally friendly method. Initially, CuO-NiO was prepared and applied for the catalytic reduction of 4-nitrophenol (4-NP). The results showed that CuO-NiO demonstrate high catalytic activity toward the reduction of 4-NP to 4-aminophenol (4-AP) with a rate constant of 2.97 × 10^-2 s^-1. Further, CuO-NiO were well-dispersed in the polymeric matrix of carboxymethyl cellulose to prepare CMC/CuO-NiO beads. CMC/CuO-NiO nanocomposite beads were also applied to catalyze the reduction of potassium ferrocyanide (K₃Fe (CN)₆), 4-NP, Congo red (CR) and Eosin yellow (EY) in the presence of sodium borohydride. Experimental data indicated that CMC/CuO-NiO nanocomposite has higher catalytic activity and high rate constant compared to CuO-NiO. The rate constant found to be 6.88 × 10^-2, 6.27 × 10^-2, 1.89 × 10^-2 and 2.43 × 10^-2 for K₃Fe(CN)₆, 4-NP, CR and EY, respectively, using 5 mg CMC/CuO-NiO beads. FE-SEM, EDX, FTER, XRD and XPS were used to characterize the nanocomposites. CMC/CuO-NiO beads catalytically reduced up to 95-99% of K₃Fe(CN)₆, 4-NP, CR and EY within 40, 60, 120 and 120 s. CMC/CuO-NiO beads were found more selective for the reduction of 4-NP. The catalytic reduction performance of CMC/CuO-NiO beads was optimized by studying the influence of different parameters on the catalytic reduction of 4-NP. Hence, the effective and super catalytic performance toward the reduction of different organic and inorganic pollutants makes CMC/CuO-NiO beads a smart material and suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial catalysts.

La(OH)3-modified magnetic sodium carboxymethyl cellulose for sequential removal of pollutants: adsorption of phosphate and subsequent photocatalytical reduction of Cr(VI)

In this study, La(OH)₃-modified magnetic sodium carboxymethyl cellulose (La-MC) was prepared as adsorbents for phosphate, which exhibited excellent adsorption performance up to 62.98 mg P/g and magnetic property for easy recovery. The recovered adsorbents after phosphate sorption were subsequently used for photocatalytic reduction of Cr(VI) and possessed good photocatalytic activity. This work provided an excellent reference for developing a new way of extending life cycle of adsorbents by combining phosphate adsorption with photocatalysis for sequential removal of pollutants from water in the future.

Effects of coating materials on antibacterial properties of industrial and sunscreen-derived titanium-dioxide nanoparticles on Escherichia coli

Organic or inorganic stabilizers are often used for coating nanoparticles (NPs) in consumer products. However, upon release of stabilized NPs into the environment, uncertainty exists as to the antimicrobial properties of NPs due to stabilizers and the resultant bioaccumulation in organisms. This study investigates antibacterial effects and subsequent mechanisms of TiO₂ NPs on Escherichia coli (E. coli) in the presence and absence of stabilizers (CMC, PVP, and SiO₂) commonly used in consumer products. Compared with uncoated TiO₂ NPs, the presence of any stabilizers tested in this study increased toxicity of NPs and enhanced growth inhibition in E. coli. While the particle sizes of TiO₂ were smaller as the result of coating with PVP or CMC and appeared to contribute to E. coli cell damage, the generation of reactive oxygen species (ROS) was independent of stabilizer type. In fact, coating with PVP and CMC exerted ROS scavenging properties. In contrast, increased ROS production was observed at higher concentrations of TiO₂ and upon coating with SiO₂. This impact of SiO₂ can be related to the formation of a TiOSi chemical bond. The results of the present study emphasize the importance of nanoparticle coating to their anti-bacterial activity and toxicity.

Microwave assisted one pot three component synthesis of propargylamine, tetra substituted propargylamine and pyrrolo[1,2-a]quinolines using CuNPs@ZnO–PTh as a heterogeneous catalyst

A Cu@ZnO–PTh nanocomposite was synthesized and used as a heterogeneous catalyst for KA² and A³ coupling, which is a highly efficient and green technique.