Synthesis of Silica Supported Perchloric Acid Nanoparticles (HClO4–SiO2 NPs): Efficient Synthesis of Biscoumarin Derivatives in Water

Effective Synthesis and Biological Evaluation of Dicoumarols: Preparation, Characterization, and Docking Studies

A series of 3,3-arylidene bis (4-hydroxycoumarins) 2 were synthesized by the reaction of aromatic aldehydes with 4-hydroxycoumarin using dodecylbenzenesulfonic acid as Brønsted acid-surfactant catalyst in aqueous media and under microwave irradiation. The present method is operationally simple and the use of water as the reaction medium makes the process environmentally benign. The epoxydicoumarins 5 were then obtained with a good yield by heating 3,3'-arylidenebis-4-hydroxycoumarins 2 in acetic anhydride. Techniques such as elemental analysis, ¹H, ¹³C-¹H NMR, and infrared spectroscopy were employed to characterize these compounds. The synthesized compounds displayed good antibacterial potential against Escherichia coli (ATCC 25988), Pseudomonas aeruginosa (ATCC 27853), Klebsilla pneumonia (ATCC 700603), Staphylococcus aureus (ATCC 29213), methicillin-resistant Staphylococcus aureus (ATCC 43300) and Candida albicans (ATCC 14053). The MIC values of 23 mg/mL for compound 5e against Escherichia coli (ATCC 25988) and 17 mg/mL for 2a were observed. Furthemore, a molecular docking simulation has been performed to evaluate the antibacterial activities and the probable binding modes of the studied compounds 2a-f and 5a-g toward the active sites of a series of well known antibacterial targets. Among the investigated compounds, the binding modes and docking scores demonstrate that 2a has the most antibacterial and antifungal activities. Additionally, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS has been tested for their ability to scavenge hydrogen peroxide and free radicals. According to our results, these compounds exhibit excellent radical scavenging properties. Furthermore, compounds 2-5 were evaluated for anti-inflammatory activity by indirect haemolytic and lipoxygenase inhibition assays and revealed good activity.

HClO4-SiO2 Nanoparticles: An Efficient and Versatile Catalyst for Synthesis of 1,4-Dihydropyrano[2,3-c]Pyrazoles

The reaction between aromatic aldehydes, malononitrile and 3-methyl-1-phenyl-2-pyrazoline-5-one catalysed by silica supported perchloric acid nanoparticles (HClO4-SiO2 nanoparticles) in solvent H2O under reflux provided a simple and efficient one-pot route for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles in excellent yields.

SiO2–OSO3H Nanoparticles: An Efficient, Versatile and New Reagent for the One-Pot Synthesis of 2-Amino-8-Oxo-4,8-Dihydropyrano[3,2-b]Pyran-3-Carbonitrile Derivatives in Water, a Green Protocol

In a one-pot three-component reaction, an aromatic or aliphatic aldehyde, malononitrile and 5-hydroxy-2-hydroxymethyl-4H-pyran-4-one were condensed for the synthesis of 2-amino-8-oxo-4,8-dihydropyrano[3,2- b]pyran-3-carbonitrile derivatives in the presence of nano-silica sulfuric acid (SiO2–OSO3H nanoparticles) in improved yields. The catalyst is recoverable by simple filtration and can be used in the subsequent reactions.