Paula S. Branco

Solvent‐Free and Catalysts‐Free Chemistry: A Benign Pathway to Sustainability

In the past decade, alternative benign organic methodologies have become an imperative part of organic syntheses and chemical reactions. The various new and innovative sustainable organic reactions and methodologies using no solvents or catalysts and employing alternative energy inputs such as microwaves, sonication, conventional and room temperature heating conditions, mechanochemical mixing, and high-speed ball milling are discussed in detail. Environmentally benign and pharmaceutically important reactions such as multicomponent, condensation, and Michael addition reactions; ring opening of epoxides; and oxidation and other significant organic reactions are discussed. An overview of benign reactions through solvent- and catalyst-free (SF-CF) chemistry and a critical perspective on emerging synergies between SF-CF organic reactions are discussed.

Magnetite-supported sulfonic acid: a retrievable nanocatalyst for the Ritter reaction and multicomponent reactions

Magnetite-sulfonic acid (Nanocat-Fe-OSO3H), prepared by the wet-impregnation method, serves as a magnetically retrievable sustainable catalyst for the Ritter and multicomponent reactions. The as synthesized catalyst can be used in several reaction cycles without any loss of activity.

Regio‐ and Chemoselective Reduction of Nitroarenes and Carbonyl Compounds over Recyclable Magnetic FerriteNickel Nanoparticles (Fe3O4Ni) by Using Glycerol as a Hydrogen Source

Reduction by magnetic nano-Fe(3)O(4)-Ni: a facile, simple and environmentally friendly hydrogen-transfer reaction that takes place over recyclable ferrite-nickel magnetic nanoparticles (Fe(3)O(4)-Ni) by using glycerol as hydrogen source allows aromatic amines and alcohols to be synthesized from the precursor nitroarenes and carbonyl compounds.

Magnetically recyclable magnetite–ceria (Nanocat-Fe-Ce) nanocatalyst – applications in multicomponent reactions under benign conditions

A novel magnetite nanoparticle-supported ceria catalyst (Nanocat-Fe-Ce) has been successfully prepared by a simple impregnation method and was characterized by XRD, SIMS, FEG-SEM-EDS, and TEM. The exact nature of Nanocat-Fe-Ce was confirmed by X-ray photoelectron spectroscopy and it is noted that CeO2 nanoparticles are supported on magnetite, with evidence of secondary ion mass spectrometry. Catalytic activity of the nano-catalyst was explored for the synthesis of dihydropyridines under benign conditions; a greener protocol is described that provides a simple and efficient method for the synthesis of functionalized 1,4-dihydropyridines using a recyclable nanocatalyst. Notably, 5.22 mol% of the catalyst is sufficient to catalyze the multicomponent reaction in ethanolic medium at room temperature. Importantly, the catalyst could be easily separated from the reaction mixture by using an external magnet and recycled several times without loss of activity.

Synthesis and characterization of versatile MgO–ZrO2 mixed metal oxide nanoparticles and their applications

A heterogeneous, versatile nano-magnesia-zirconia or MgO–ZrO2 (MZ) catalyst was prepared by an ultra dilution method. The as-synthesised catalyst was characterized by several analytical techniques such as XRD, particle size analysis, BET surface area, thermogravimetric analysis (TGA), differential thermal analysis (DTA), FT-IR spectroscopy, SEM (scanning electron microscope), TEM (transmission electron microscope) and XPS (X-ray fluorescence spectroscopy). The surface area is found to be 268 m2 g−1. The catalytic activity of MZ was tested for various important organic reactions such as cross-aldol condensation, N-benzyloxycarbonylation of amines, reduction of aromatic nitrocompounds, and synthesis of 1,5-benzodiazepines. It has been observed that for all reactions MZ shows a good catalytic activity. All corresponding products were obtained in good to excellent yield under mild conditions. The MgO-ZrO2 catalyst can be prepared from inexpensive precursors, has high surface area, and is reusable and recyclable for all reactions.

A facile synthesis of cysteine–ferrite magnetic nanoparticles for application in multicomponent reactions—a sustainable protocol

A facile, simple and environmentally friendly Fe3O4–cysteine MNP was synthesized without any additive or additional source of linkers. Fe3O4–cysteine MNPs were successfully used for the synthesis of β-amino carbonyl and hydroquinoline compounds, which were obtained in excellent yields via multicomponent reactions. Magnetic organocatalysts can be easily recovered by simple magnetic decantation and their catalytic activity remains unaltered after 9 consecutive cycles, making them environmentally friendly and widely applicable due to their efficiency, ease of handling, and cost effectiveness.

First application of core-shell Ag@Ni magnetic nanocatalyst for transfer hydrogenation reactions of aromatic nitro and carbonyl compounds

A magnetically separable core-shell Ag@Ni nanocatalyst was prepared by a simple one-pot synthetic route using oleylamine both as solvent and reducing agent and triphenylphosphine as surfactant. The synthesized nanoparticles were characterized by several techniques such as X-ray diffraction pattern (XRD), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern, and energy dispersive X-ray spectroscopy (EDS). The core-shell Ag@Ni nanocatalyst was found to have very excellent activity for the transfer hydrogenation reactions of aromatic nitro and carbonyl compounds under mild conditions using isopropyl alcohol as hydrogen donor. Excellent chemoselectivity and regioselectivity for the nitro group reduction was demonstrated.

An efficient and expeditious Fmoc protection of amines and amino acids in aqueous media

A new and environmentally friendly Fmoc protection of a variety of aliphatic and aromatic amines, amino acids, amino alcohols and amino phenols is reported in aqueous media under mild and catalyst-free conditions. The reaction proved to be chemoselective in presence of ambident nucleophiles.

Convenient Synthesis of 3-Vinyl and 3-Styryl Coumarins

A variety of 2-hydroxy aldehydes on reaction with 3-butenoic acid afford in a one-pot reaction the corresponding 3-vinylcoumarins. As expected, extension of the delocalized π-electron system accomplished by Heck coupling reactions with aryl halides results in an increased fluorescence of the compounds whose applicability is yet to be established.

Pro-oxidant effects of Ecstasy and its metabolites in mouse brain synaptosomes.

3,4‐Methylenedioxymethamphetamine (MDMA or ‘Ecstasy’) is a worldwide major drug of abuse known to elicit neurotoxic effects. The mechanisms underlying the neurotoxic effects of MDMA are not clear at present, but the metabolism of dopamine and 5‐HT by monoamine oxidase (MAO), as well as the hepatic biotransformation of MDMA into pro‐oxidant reactive metabolites is thought to contribute to its adverse effects.