Uric Acid as a Naturally Biodegradable and Reusable Catalyst for the Convenient and Eco-Safe Synthesis of Biologically Active Pyran Annulated Heterocyclic Systems

Unexpected synthesis of 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl-H-sulfite as a catalyst for the synthesis of pyrazolophthalazines

Several attempts for preparation of 4,4'-(2-thioxoimidazolidine-1,3-diyl)bis(butane-1-sulfonic acid) were not successful despite taking 2 mmol of 1,4-butane sultone in reaction with 1 mmol of imidazolidine-2-thione. Instead, 4-(4,5-dihydro-1H-imidazol-2-ylsulfanyl)butyl hydrogen sulfite (DISBHS) was prepared unexpectedly, characterized and used for the synthesis of diverse pyrazolophthalazines from the one-pot three component condensation reaction of phthalhydrazide, malononitrile and aldehydes under mild conditions.

Synthesis and characterization of an Fe-MOF@Fe3O4 nanocatalyst and its application as an organic nanocatalyst for one-pot synthesis of dihydropyrano[2,3-c]chromenes

In this study, the recyclable heterogeneous cluster bud Fe-MOF@Fe₃O₄ 'nanoflower' composite (CB Fe-MOF@Fe₃O₄ NFC) was successfully synthesized using Fe(NO₃)₃·9H₂O, 8-hydroxyquinoline sulfate monohydrate, and Fe₃O₄ nanoparticles by microwave irradiation. The as-prepared CB Fe-MOF@Fe₃O₄ NFC was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), vibrational sampling magnetometry (VSM), and Fourier transform infrared spectroscopy (FTIR). The CB Fe-MOF@Fe₃O₄ NFC samples proved to have excellent catalytic activity. The activity of the CB Fe-MOF@Fe₃O₄ NFC nanocatalyst was explored in the synthesis of dihydropyrano[3, 2-c]chromene derivatives via a three-component reaction of 4-hydroxycoumarin, malononitrile, and a wide range of aromatic aldehyde compounds. Optimized reaction conditions had several advantages, including the use of water as a green solvent, environmental compatibility, simple work-up, reusability of the catalyst, low catalyst loading, faster reaction time, and higher yields.

Urea hydrogen peroxide-initiated synthesis of pyranopyrazoles through oxidative coupling under base- and metal-free conditions by physical grinding method

A novel multicomponent one-pot expeditious synthesis of highly functionalized and pharmaceutically fascinated pyranopyrazoles has been developed. This reaction occurs via tandem Knoevenagel condensation reaction of methyl aryl derivatives, 3-methyl pyrazolone and malononitrile in the presence of urea hydrogen peroxide under the physical grinding method. The present methodology offers several benefits such as available green and cheap starting materials, solvent-free, mild reaction conditions, high atom economy, eco-friendly standards, excellent yields and easy isolation of the products without column chromatographic separation.