Recyclable Bi₂WO₆-nanoparticle mediated one-pot multicomponent reactions in aqueous medium at room temperature

Abstract

Room temperature multicomponent reactions (MCRs) are reported using Bi2O3, BiVO4, and Bi2WO6 (nanoparticle) as heterogeneous catalysts. Among these, Bi2WO6 (5 mol%) nanoparticles showed excellent reactivity for the synthesis of functionalized dihydropyridine, polyhydroquinoline, 4H-chromene and 2-amino-4H-benzo[b]pyran derivatives in aqueous medium.

Pyrazole-carboxaldehydes as versatile precursors for different pyrazole-substituted heterocyclic systems

“…Under various conditions, the Hantzsch condensation reaction of pyrazole-4-carboxaldehyde 2 with βketoester 64 and ammonium acetate or ammonia afforded the corresponding dihydropyridines 182. 131,[176][177][178][179][180][181][182][183] Similarly, N-aryl-1,4-dihydropyridines 183 were prepared by heating the 1,3-diphenyl-1H-pyrazole-4carboxaldehyde 2, ethyl acetoacetate/acetylacetone 64 and substituted anilines 184 165 Also, it was reported that the cyclocondensation of pyrazole-carboxaldehyde 2 with urea 120 or thiourea 184 120,185 and ethyl cyanoacetate 64 in the presence of sodium ethoxide 120 or potassium carbonate 185 gave the corresponding 2-oxo(thioxo)pyrimidine derivatives 185 (Scheme 79).…”

β‐Cyclodextrin: A Green and Efficient Supramolecular Catalyst for Organic Transformations

“…Recent literature reveals that the 1,4‐dihydropyridine derivatives act as glycoprotein inhibitor, calcium channel blockers, antimitotic agent, anticancer and antitubercular agents . Hantzsch diethyl 1,4‐dihydro‐2,6‐dimethyl‐3,5‐pyridinedicarboxylate also act as a good source of hydride for reduction purpose, Some literature reports for dihydropyridine synthesis includes immobilized metallic phthalocyanines, hollow Fe 3 O 4 @DA‐SO 3 H as heterogeneous nano magnetic acid catalyst, Bi 2 BWO 6 nanoparticles, in situ generated HCl, etc. A number of the reported protocols to synthesize dihydropyridines requiring solvents and catalysts are not acceptable in the context of green synthesis; utilize reagents and catalysts which are either toxic or expensive and stoichiometric use of reagents with respect to reactant.…”

Synthesis and characterization of sodium polyaspartate‐functionalized silica‐coated magnetite nanoparticles: A heterogeneous, reusable and magnetically separable catalyst for the solvent‐free synthesis of 2‐amino‐4H‐chromene derivatives

“…All reagents were used without further purification and were procured from commercial sources. Melting points [30] 2 Imidazole (0.2 mmol) EtOH, reflux 1 h 86 [25] 3 TBAC (10 mol%) c Solvent-free, 100°C 35 min 82 [42] 4 Nano CP (0.01 g) d H 2 O, reflux 20 min 95 [29] 5 POPI (5 mol%) e Ball milling, ambient 13 min 97 [26] 6 ZnFe 2 O 4 NPs (40 mg) H 2 O, R.T. 3 h 93 [43] 7 Saturated K 2 CO 3 (10 ml) H 2 O, mw 3.2 min 90 [44] 8 Gel entrapped DABCO (1 g) EtOH, ambient 10 min 93 [45] 9 CAN (5 mol%) Solvent-free, 120°C 30 min 91 [46] 10 [bmim]OH (0.5 mmol) H 2 O, reflux 60 min 90 [33] 11 Na 2 CO 3 (0.1 mmol) Solvent-free, 125°C 40 min 100 [47] 12 SBA-DABCO (0.125 g) H 2 O, 80°C 25 min 87 [48] 13 5-Å MS (0.5 g) Solvent-free, MW 5 min 95 [49] 14 with TMS as an internal standard. The X-ray diffraction (XRD) was performed on Philips X-Pert (Cu-Ka radiation, λ = 0.15405 nm) in the range of 2θ = 20-80°using 0.04°as the step length.…”