Equisetum arvense As an abundant source of silica nanoparticles. SiO₂/H₃PW₁₂O₄₀ nanohybrid material as an efficient and environmental benign catalyst in the synthesis of 2‐amino‐4H‐chromenes under solvent‐free conditions

Abstract

Uniform SiO 2 nanoparticles were successfully prepared from Equisetum arvense obtained from the north-east of Iran. Then, surface modification of the extracted nanoparticles was performed with a methanol solution of H 3 PW 12 O 40 via wet impregnation method. The prepared nanocatalyst was characterized by XRD, FESEM, ICP, UV-Vis, and FT-IR spectroscopy. The supported heterogeneous nanocatalyst was successfully applied as a Lewis/Bronsted acid catalyst in the synthesis of a series of substituted 4H-chromenes via condensation of aromatic aldehydes, malononitrile, and 4-hydroxycoumarin under solventless conditions with fine yields in appropriately short times.

The dual role of ammonium acetate as reagent and catalyst in the synthesis of 2, 4, 5-triaryl-1H-imidazoles

“…In connection with our ongoing work on the synthesis of various heterocyclic compounds [22][23][24][25][26][27][28][29], we wish to report a facile procedure for preparation of imidazole derivatives without addition of any specific catalyst. As mentioned above, several methods are introduced for the synthesis of trisubstitutedimidazoles and their derivatives.…”

Ag3[PMo12O40]: An efficient and green catalyst for the synthesis of highly functionalized pyran‐annulated heterocycles via multicomponent reaction

“…To reveal the advantages of this catalyst, its catalytic activity in the model reaction involving benzaldehyde, malononitrile and 4‐hydroxycoumarin was compared with those of previously reported systems (Table ). As evident from Table , the catalytic activity of Ag 3 PMo 12 O 40 was compared with other catalysts such as [DMAP‐PEG 1000 ‐DI L][BF 4 ], nano‐ZnO, crown ether complex cation ionic liquids (CECILs), ammonium acetate, titanium dioxide nanowires, nanomagnetic double‐charged diazoniabicyclo[2.2.2]octane dichloride silica hybrid (Fe 3 O 4 @SiO 2 /DABCO), surfactant‐modified bentonite (CTMAB‐bentonite), hexamethylenetetramine, SiO 2 /H 3 PW 12 O 40 nanohybrid, RuBr 2 (PPh 3 ) 4 , sodium malonate, NaCl, (NH 4 ) 42 [MoVI 72 MoV 60 O 372 (CH 3 COO) 30 (H 2 O) 72 ], a Keplerate‐type giant‐ball nanoporous isopolyoxomolybdate, silica‐supported molybdic acid, KNaC 4 H 4 O 6 ⋅4H 2 O (potassium sodium tartrate) and polypyrrole/Fe 3 O 4 /CNT that were previously used as catalysts in the same reaction. The results showed that compared to the other catalysts, our designed catalyst can catalyse the reaction in an appropriate manner.…”

Guanine‐La complex supported onto SBA‐15: A novel efficient heterogeneous mesoporous nanocatalyst for one‐pot, multi‐component Tandem Knoevenagel condensation–Michael addition–cyclization Reactions

“…Tandem reactions offer many opportunities to improve chemical transformations such as Lewis acid–base catalysis, hydrogenation reactions and alkene metathesis . MCRs are currently well‐established methods for the synthesis of heterocycles, natural products and polymers while Double and Triple Cascade Reactions are still a growing field of research. Knoevenagel condensation–Michael addition (Double Cascade Reactions) and Knoevenagel condensation–Michael addition–cyclization (Triple Cascade Reactions) Sequences have been widely studied and frequently applied to the synthesis of natural products and biologically active compounds .…”