Synthesis of Pyranopyrazoles Using Magnetically Recyclable Heterogeneous Iron Oxide‐silica Core‐shell Nanocatalyst

Abstract

The Fe 3 O 4 @SiO 2 core-shell nanocatalyst were prepared and efficiently used for four-component coupling reaction of aromatic aldehydes, malononitrile, ethyl acetoacetate and hydrazine hydrate in water/ethanol mixture. Various aromatic aldehydes possessing electron-withdrawing and electron-donating groups in different positions on the ring were successfully transformed to substituted pyranopyrazoles in high yields in short time. The nanocatalyst was easily recovered, and reused five times without significant loss in catalytic activity and performance. The structure, size and morphology of the nanosized catalyst were studied by various techniques such as Fourier transform infrared spectroscopy, powder X-ray diffraction, dynamic light scattering and transmission electron microscopy.

Green Synthesis of Pyrazoles: Recent Developments in Aqueous Methods

“…Fe 3 O 4 @SiO 2 core-shell NPs were used by Soleimani, Jafarzadeh, and co-workers for the construction of fused pyrazoles in H 2 O/EtOH (Scheme 20). 50 The application of biodegradable -cyclodextrin (-CD) as a catalyst in the four-reactant domino synthesis of pyrano[2,3-c]pyrazoles 12 and spiro[indoline-3,4-pyrano[2,3c]pyrazole] products 15 and 18 was explored by Dalal and co-workers in 2015. The reaction progressed successfully with ethyl acetoacetate, malononitrile, NH 2 NH 2 •H 2 O, and aldehydes (aryl or hetaryl)/1,5-disubstituted isatins/1,1-(butane-1,4-diyl)bis(indoline-2,3-dione) in H 2 O/EtOH (9:1) at 80 °C (Scheme 13).…”

Applications of pyrazolone in multicomponent reactions for the synthesis of dihydropyrano[2,3-c]pyrazoles and spiro-pyrano[2,3-c]pyrazoles in an aqueous medium

“…All electron-withdrawing group, as well as the electron-donating group on different positions of the aromatic ring, were successfully transformed into the corresponding product in a very short reaction time (Scheme 47). 98 Scheme 47. Synthesis of dihydropyrano [2,3-c]pyrazoles 37 developed by Ebrahim.…”

Synthesis of pyrano[2,3‐c]pyrazoles: A review

“…The synthesis of 1,4‐dihydropyranopyrazoles 36 under the catalytic action of various nano‐catalysts, including iron oxide‐silica core‐shell nanocatalyst (Fe 3 O 4 @SiO 2 NPs), [ 85 ] Preyssler heteropoly acid supported on silica‐coated NiFe 2 O 4 MNPs (NFS‐PRS), [ 86 ] Ag/TiO 2 nano‐thin films. [ 87 ] and silica nanoparticles from wheat straw (WS‐SiO 2 NPs).…”