Abstract
A superparamagnetic graphene oxide/Fe3O4/l-proline nano hybrid that was obtained from the non-covalent immobilization of l-proline on graphene oxide/Fe3O4 nanocomposite was used as a new magnetically separable catalyst for the efficient synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives. The prepared heterogeneous catalyst was characterized using FTIR, TGA, DTG, XRD, TEM, SEM, and elemental analysis techniques. Short reaction times (5–15 min), excellent yields (87–98%), and simple experimental procedure with an easy work-up are some of the advantages of the introduced catalyst.
Highlights
In recent years, carbocatalysis has attracted much attention, as it is cheap and can be obtained.Catalysts based on carbon constituents, such as activated carbon and carbon nanotubes, have been used as catalyst supports [1]
When considering the above mentioned argument, we recently introduced a new facile and cheap methodology for the preparation of L-prolinate-amberlite adduct by using ion-pair immobilization of L-proline on the surface of commercially available amberlite IRA-900OH as a heterogeneous and recoverable organocatalyst for the efficient synthesis of 2-amino-4H-chromenes [27], spiroindoles [28], 3,30 -diaryloxindoles [29], bis-pyrazoles [30], 4H-pyrano[2,3-c] pyrazole derivatives [31], and biscoumarin derivatives [32]
The concise method for the preparation of graphene oxide (GO)/Fe3 O4 /L-proline is illustrated in Scheme 1
Summary
Carbocatalysis has attracted much attention, as it is cheap and can be obtained.Catalysts based on carbon constituents, such as activated carbon and carbon nanotubes, have been used as catalyst supports [1]. Graphene and graphene oxide (GO) are emerging as a novel class of carbocatalysts, as well as catalyst supports in organic synthesis [2,3]. GO has been proved as a favorable support due to its inherent properties, such as high chemically stability, large surface area, and good availability [4]. GO has functional groups, mainly including epoxide, hydroxyl, and carboxyl on the edge, top, and bottom surface of each sheet that even after sufficient reduction, cannot be completely removed which makes GO a suitable support for metal and metal oxide nanoparticles [5]. GO owing its surface decorated myriad oxygenated functions and conductivity with very high surface area has been used in sensors, nanoelectronics, contaminant removal, drug delivery, as metal-free catalysts or as supports for immobilizing active species for facilitating synthetic transformations. Among the various uses of GO, assembling other inorganic materials, like
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