Valeria Palermo

This study explores the oxidation reaction of sulfide groups present in methyl 1-(4-chlorophenyl)-4-((4-chlorophenyl)amino)-2,6-bis(4-(methylthio)phenyl)-1,2,5,6-tetrahydropyridine-3-carboxylate towards the corresponding sulfoxide and sulfone, under green reaction conditions: ethanol as solvent, aqueous hydrogen peroxide as oxidant agent, phosphomolybdic acid as redox catalyst at atmospheric pressure. The optimum conditions for obtaining the sulfoxide were 0.2 mmol substrate, 0.34 mL H₂O₂ 30% w/V, 1% mol phosphomolybdic acid, ethanol at 50 °C for 15 h; meanwhile, the sulfone was obtained at the reflux temperature. To our knowledge, neither the oxidation reaction of the sulfur atom in tetrahydropyridines nor the corresponding sulfoxides and sulfones are reported in the literature.

A multicomponent protocol for the synthesis of 1,2,5,6-tetrahydropyridines catalyzed by silica-supported phosphomolybdic acid (5PMo@SiO₂) prepared by the sol–gel method was optimized. The influence of temperature and solvent was systematically investigated. The optimized conditions afforded the model tetrahydropyridine in 67% isolated yield after 7 h under reflux in methanol. The methodology was subsequently applied to the synthesis of ten structurally diverse tetrahydropyridine derivatives in moderate-to-good yields (67–77%), demonstrating broad substrate compatibility and good reproducibility upon scale-up. These results highlight the efficiency and versatility of the developed catalytic system for the preparation of functionalized tetrahydropyridines with potential antifouling applications.

Los disolventes eutécticos profundos (DES) han emergido como una opción sostenible frente a los disolventes orgánicos tradicionales en el marco de la química verde y la valorización de biomasa lignocelulósica. Este trabajo analiza de manera integral sus propiedades fisicoquímicas, métodos de síntesis y aplicaciones en la producción de moléculas plataforma de alto valor añadido, tales como 5-hidroximetilfurfural (HMF), ácido levulínico (AL), furfural y derivados furánicos. Los DES, formados por combinaciones de aceptores y donadores de enlaces de hidrógeno, presentan beneficios como baja toxicidad, biodegradabilidad, bajo costo y propiedades ajustables, lo que favorece su implementación en procesos sostenibles. En el contexto de biorrefinerías, los DES facilitan el pretratamiento de biomasa al reducir su recalcitrancia estructural mediante la disrupción de las redes lignocelulósicas, mejorando la accesibilidad a polisacáridos. Asimismo, actúan como medios de reacción y catalizadores en sistemas homogéneos, lo que incrementa la eficiencia en la conversión de carbohidratos en compuestos de valor. Se destacan aplicaciones en sistemas bifásicos, procesos asistidos por microondas y estrategias integradas de conversión-extracción, con rendimientos elevados y condiciones operativas moderadas. Particularmente, los DES ácidos han demostrado alta eficacia en la extracción de ácido levulínico, alcanzando rendimientos superiores al 70 % y eficiencias de carbono cercanas al 100 %. Además, su capacidad de reutilización y su integración en procesos de una sola etapa reducen costos y complejidad operativa. En conjunto, los DES se consolidan como herramientas versátiles para el desarrollo de procesos químicos más eficientes, selectivos y ambientalmente sostenibles.

In this work, biscoumarin molecules were obtained by a multicomponent reaction, without catalysts, under thermal heating or microwave irradiation. First, optimization tests were performed using benzaldehyde and 4-hydroxycoumarin as starting substrates. The optimal temperature (100 °C), solvent (1-propanol), and reaction time (4 h for conventional heating and 1 h for microwave irradiation) were then employed for the reaction between 4-hydroxycoumarin and different 3-formylchromones to obtain biscoumarins. Good yields and selectivity, which in most cases were greater than 65%, both with conventional thermal heating and microwave radiation, were achieved.

Heteropolyacids (HPAs) are well known for their application as catalysts in organic synthesis owing to their oxidizing capabilities and strong Brönsted acidity. However, a notable drawback of HPAs is their solubility in various reaction media, which has prompted the development of strategies to convert them into heterogeneous catalysts through immobilization on diverse materials. This review aims to describe recent advancements in the utilization of alumina as a support for HPAs and their applications as heterogeneous catalysts in the synthesis of organic compounds. Various strategies, methodologies, loading techniques, and the nature of HPAs, along with their acid and redox properties, are analyzed and compared. Several organic reactions, including oxidation processes, esterification, and the condensation synthesis of heterocycles, such as chromones and pyrroles, are explored.

We report the synthesis of alkyl 1,2,6‐triaryl‐4‐arylaminopiperidine‐3‐ene‐3‐carboxylates in acceptable yields (42%–71%) and high trans ‐diastereoselectivity (69:31 to 100:0) through a one‐pot multicomponent reaction of aromatic aldehydes, aromatic amines, and β ‐ketoesters catalyzed by phosphomolybdic acid in methanol at room temperature. The structure and stereochemistry of tetrahydropyridines were confirmed by X‐ray crystallography. This protocol stands out for its operational simplicity, the use of an inexpensive and commercially available heteropolyacid catalyst, low catalyst loading, and purification via simple filtration, resulting in acceptable yields and high diastereoselectivity.

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.

The conversion of residual biomass from fruit seeds into biochar can be achieved using MgCl₂ as an activating agent and calcining at 700 °C. The resulting MgO‐biochars were employed in the aldol condensation reaction between furfural and acetone. This reaction is essential as the first step in the obtention of biofuels derived from biomass. The biochars were characterized through various physicochemical techniques, revealing that the presence of MgO nanoparticles deposited on the carbon surface modifies the structural and acidic‐basic properties of the carbonaceous materials with a graphitic structure. The biochar with a surface content of MgO of 0.34 % w/w enables the achievement of 100 % of selectivity towards 4‐(2‐furanyl)‐3‐buten‐2‐one (I) with quantitative conversions under optimized conditions. This property highlights the potential of using this type of biochar, commonly used for CO₂ capture, as a versatile acidic‐basic catalyst, thereby introducing a novel approach to sustainable chemistry.