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Reactions, Volume 6, Issue 3 (September 2025) – 5 articles

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15 pages, 1342 KiB  
Article
Synthesis of 6-Arylaminoflavones via Buchwald–Hartwig Amination and Its Anti-Tumor Investigation
by Karinne E. Prado, Micael R. Cunha, Gabriela A. Moreira, Karoline B. Waitman, Neuza M. A. Hassimotto, Katlin B. Massirer, Monica F. Z. J. Toledo and Roberto Parise-Filho
Reactions 2025, 6(3), 42; https://doi.org/10.3390/reactions6030042 (registering DOI) - 31 Jul 2025
Abstract
A new series of 6-arylaminoflavones was synthesized via the Buchwald–Hartwig cross-coupling reaction, aiming to functionalize the flavone core efficiently. Reaction optimization revealed that Pd2(dba)3/XantPhos with Cs2CO3 in toluene provided the best yields, with isolated yields ranging [...] Read more.
A new series of 6-arylaminoflavones was synthesized via the Buchwald–Hartwig cross-coupling reaction, aiming to functionalize the flavone core efficiently. Reaction optimization revealed that Pd2(dba)3/XantPhos with Cs2CO3 in toluene provided the best yields, with isolated yields ranging from 8% to 95%, depending on the arylamine structure. Steric hindrance and electron-withdrawing groups at the arylamine ring impacted the reaction outcomes. Cytotoxicity assays in different human cancer cell lines indicated that substitution patterns at both the arylamine and B-rings strongly impacted biological activity. In particular, compounds bearing a 3,4-dimethoxy substitution at the B-ring and a trifluoromethyl (13c) or chlorine (13g) group at the aniline moiety exhibited enhanced cytotoxicity. These findings provide insights into the structure–activity relationship of 6-arylaminoflavones while contributing to the development of synthetic methodologies for functionalized flavones. Full article
(This article belongs to the Special Issue Advances in Organic Synthesis for Drug Discovery and Development)
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13 pages, 1111 KiB  
Communication
Renewable Solvents for Diels–Alder/Cheletropic Reaction Sequences: Preparation of Pentaphenylbenzene and 1,2,4-Triphenyltriphenylene
by Sara Ahmed, Harry Burrows, Brian A. Chalmers, David B. Cordes, Ruairidh Macleod Davidson, Lauren Emmens, Theodore V. Fulton, Daniel Kleinjan, Iain L. J. Patterson and Iain A. Smellie
Reactions 2025, 6(3), 41; https://doi.org/10.3390/reactions6030041 - 30 Jul 2025
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Abstract
Polycyclic aromatic compounds can often be made by a sequence featuring an initial Diels–Alder [4 + 2] cycloaddition reaction, followed by cheletropic extrusion of carbon monoxide. These reactions normally require heating the diene and dieneophile in petrochemical-derived aromatic hydrocarbon solvents, such as xylenes [...] Read more.
Polycyclic aromatic compounds can often be made by a sequence featuring an initial Diels–Alder [4 + 2] cycloaddition reaction, followed by cheletropic extrusion of carbon monoxide. These reactions normally require heating the diene and dieneophile in petrochemical-derived aromatic hydrocarbon solvents, such as xylenes or diphenyl ether. This article summarizes the results of attempts to use renewable solvents in place of those currently in use to prepare pentaphenylbenzene and 1,2,4-triphenyltriphenylene. Dihydrolevoglucosenone, p-cymene, ethyl lactate, diethyl carbonate, and cyclopentyl methyl ether have all been successfully evaluated as renewable solvent alternatives in Diels–Alder/cheletropic reaction sequences. An analysis of the products from the reactions investigated did not show evidence of oxidative degradation of the diene reactants. Furthermore, norbornadien-7-one intermediates were not isolated from any of the reactions tested. Full article
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15 pages, 12959 KiB  
Article
Sodium Oxide-Fluxed Aluminothermic Reduction of Manganese Ore with Synergistic Effects of C and Si Reductants: SEM Study and Phase Stability Calculations
by Theresa Coetsee and Frederik De Bruin
Reactions 2025, 6(3), 40; https://doi.org/10.3390/reactions6030040 - 28 Jul 2025
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Abstract
Aluminothermic reduction is an alternative processing route for the circular economy because Al is produced electrochemically in the Hall–Héroult process with minimal CO2 emissions if the electricity input is sourced from non-fossil fuel energy sources. This circular processing option attracts increased research [...] Read more.
Aluminothermic reduction is an alternative processing route for the circular economy because Al is produced electrochemically in the Hall–Héroult process with minimal CO2 emissions if the electricity input is sourced from non-fossil fuel energy sources. This circular processing option attracts increased research attention in the aluminothermic production of manganese and silicon alloys. The Al2O3 product must be recycled through hydrometallurgical processing, with leaching as the first step. Recent work has shown that the NaAlO2 compound is easily leached in water. In this work, a suitable slag formulation is applied in the aluminothermic reduction of manganese ore to form a Na2O-based slag of high Al2O3 solubility to effect good alloy–slag separation. The synergistic effect of carbon and silicon reductants with aluminium is illustrated and compared to the test result with only carbon reductant. The addition of small amounts of carbon reductant to MnO2-containing ore ensures rapid pre-reduction to MnO, facilitating aluminothermic reduction. At 1350 °C, a loosely sintered mass formed when carbon was added alone. The alloy and slag chemical analyses are compared to the thermochemistry predicted phase chemistry. The alloy consists of 66% Mn, 22–28% Fe, 2–9% Si, 0.4–1.4% Al, and 2.2–3.5% C. The higher %Si alloy is formed by adding Si metal. Although the product slag has a higher Al2O3 content (52–55% Al2O3) compared to the target slag (39% Al2O3), the fluidity of the slags appears sufficient for good alloy separation. Full article
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14 pages, 1078 KiB  
Article
Studies on a New 1,3,4-Oxadiazole Bixin Dimer for Potential Application in Dye-Sensitized Solar Cells
by Afonso Santine M. M. Velez, Daniela Pinheiro, Carlos Serpa, Rosane Nora Castro, Marco Edilson Freire de Lima and Otávio Augusto Chaves
Reactions 2025, 6(3), 39; https://doi.org/10.3390/reactions6030039 - 13 Jul 2025
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Abstract
Dye-sensitized solar cells (DSSCs) have emerged as a promising technology for converting sunlight into electricity at a low cost; however, it is still necessary to find a photostable, low-cost, and efficient photosensitizer. In this sense, the natural product bixin (Dye 1) [...] Read more.
Dye-sensitized solar cells (DSSCs) have emerged as a promising technology for converting sunlight into electricity at a low cost; however, it is still necessary to find a photostable, low-cost, and efficient photosensitizer. In this sense, the natural product bixin (Dye 1) has previously been reported as a potential photosensitizer. Thus, the present work reports the full synthesis of diester and diacid hybrids (Dyes 2 and 3, respectively, with corresponding yields of 93% and 52%) using the natural product bixin as a starting material and 1,3,4-oxadiazole ring as a connected point. The hydrolysis step of Dye 2 aims to obtain Dye 3 with a structural capacity to anchor the titanium dioxide (TiO2) nanofilms via the carboxylic acid group. Both compounds (Dyes 1 and 3) can be adsorbed via pseudo-first order on the surface of TiO2 nanofilms, reaching saturation after 10 and 6 min of exposure in an organic solution (1 × 10−5 M), respectively, with adsorption kinetics of the semisynthetic compound almost twofold higher than the natural product. Contrary to expectations, Dye 3 had spectral behavior similar to Dye 1, but with better frontier molecular orbital (FMO) parameters, indicating that Dye 3 will probably behave very similarly or have slightly better photovoltaic performance than Dye 1 in future DSSC measurements. Full article
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32 pages, 11334 KiB  
Article
Photocatalytic Degradation of Petroleum Wastewater Using ZnO-Loaded Pistachio Shell Biochar: A Sustainable Approach for Oil and COD Removal
by Eveleen A. Dawood, Thamer J. Mohammed, Buthainah Ali Al-Timimi and Eman H. Khader
Reactions 2025, 6(3), 38; https://doi.org/10.3390/reactions6030038 - 4 Jul 2025
Viewed by 471
Abstract
The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to [...] Read more.
The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to treat such wastewater using a photocatalyst composed of biochar derived from pistachio shells and loaded with zinc oxide (ZnO) nanoparticles. The biochar-ZnO composite was prepared via a co-precipitation-assisted pyrolysis method to evaluate its efficiency in the photocatalytic degradation of petroleum wastewater (PW). The synthesized material was characterized using various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, to determine surface morphology, crystal structure, and functional groups present on the catalyst surface. Photocatalytic degradation experiments were conducted under UV and sunlight for 90 h of irradiation to evaluate the performance of the proposed system in removing oil and reducing COD levels. Key operational parameters, such as pH (2–10), catalyst dosage (0–0.1) g/50 mL, and oil and COD concentrations (50–500) ppm and (125–1252) ppm, were optimized by response surface methodology (RSM) to obtain the maximum oil and COD removal efficiency. The oil and COD were removed from PW (90.20% and 88.80%) at 0.1 g/50 mL of PS/ZnO, a pH of 2, and 50 ppm oil concentration (125 ppm of COD concentration) under UV light. The results show that pollutant removal is slightly better when using sunlight (80.00% oil removal, 78.28% COD removal) than when using four lamps of UV light (77.50% oil removal, 75.52% COD removal) at 0.055 g/50 mL of PS/ZnO, a pH of 6.8, and 100 ppm of oil concentration (290 ppm of COD concentration). The degradation rates of the PS/ZnO supported a pseudo-first-order kinetic model with R2 values of 0.9960 and 0.9922 for oil and COD. This work indicates the potential use of agricultural waste, such as pistachio shells, as a sustainable source for producing effective catalysts for industrial wastewater treatment, opening broad prospects in the field of green and nanotechnology-based environmental solutions in the development of eco-friendly and effective wastewater treatment technologies under solar light. Full article
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