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

Abstract

A facile, efficient and eco‐friendly catalytic protocol was developed for the synthesis of medicinally important pyran‐annulated heterocycles via multicomponent reaction (MCR). Cyclocondensation of differently substituted aromatic aldehydes, malononitrile/ethyl cyanoacetate and various β‐dicarbonyl compounds in the presence of Ag3[PMo12O40]⋅nH2O as heterogeneous catalyst, in EtOH–H2O, afforded diverse pyran‐fused chromene analogues. The merits observed for this approach were it being conducted via MCR, using commercially available or easily accessible starting materials in the presence of a green and easily separable heterogeneous and reusable catalyst, and affording high yields of desired products in very short reaction times with high purity in one‐pot fashion, thus providing a superior alternative approach for the synthesis of pyran‐annulated heterocycles.

Recent Progress in the Multicomponent Synthesis of Pyran Derivatives by Sustainable Catalysts under Green Conditions

“…Tamimi and co-workers [ 85 ] have studied the use of the silver complex of phosphorous molybdate (Ag 3 [PMo 12 O 40 ]) in the preparation of tetrahydro-pyran ( 92 ) moieties under green conditions. The catalyst was prepared by dissolving silver nitrate into an aqueous medium with continuous stirring at room temperature, to which H 3 [PMo 12 O 40 ] was added dropwise till the yellow precipitate was separated.…”

[CMMIM][BF4–] Ionic Liquid-Catalyzed Facile, One-Pot Synthesis of Chromeno[4,3-d]pyrido[1,2-a]pyrimidin-6-ones: Evaluation of Their Photophysical Properties and Theoretical Calculations

“…Abundant reports have been made regarding the clinical uses of some of the fused coumarins (Figure b). So, research on the construction of several new catalogues of polyfunctionalized heterocycles including isoquinolino-, indolo-quinazolines, pyrans, and so on is of great importance. − …”

Heterogeneous Catalysis by Polyoxometalates in Metal–Organic Frameworks

“…27 In addition, Lewis acidity can be achieved using high-valent metal centers with unoccupied d orbitals. 28,29 The oxidative activity of POMs can be tuned by using easily reducible metal sites, so often POM chemists turn to vanadium-substituted POMs for advanced oxidation processes. 30 POM functionalization is possible by incorporation of metal ions from throughout the periodic table, a universal concept that has been used for applications from catalysis and energy conversion to molecular electronics, nanomaterials design, biology, and medicine.…”

“…While POMs are known for their Brønsted acidity, , their structures can be tuned to make the POMs reactive Brønsted base catalysts by introducing high-charge-density terminal oxido ligands . In addition, Lewis acidity can be achieved using high-valent metal centers with unoccupied d orbitals. , The oxidative activity of POMs can be tuned by using easily reducible metal sites, so often POM chemists turn to vanadium-substituted POMs for advanced oxidation processes . POM functionalization is possible by incorporation of metal ions from throughout the periodic table, a universal concept that has been used for applications from catalysis and energy conversion to molecular electronics, nanomaterials design, biology, and medicine. − In addition, covalent attachment of organic groups to POMs is possible using suitable anchoring groups (phosphonates, sianols, carboxylates), so that linkage of metal oxide and organic chemistry − / metal complex chemistry − becomes possible.…”