The Immobilized Zirconocene Chloride on Magnetite‐reduced Graphene Oxide: A Highly Efficient and Reusable Heterogeneous Nanocatalyst for One‐pot Three‐component Synthesis of Tetrahydrobenzo[b]pyrans and Dihydropyrano[3,2‐c]chromenes

Abstract

The present paper describes the synthesis and characterization of the functionalized magnetite reduced graphene oxide (rGO@Fe3O4) with zirconocene dichloride as rGO@Fe3O4@ZrCp2Cl2. The prepared magnetic nanomaterial was characterized by Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), inductively coupled plasma optical emission spectroscopy (ICP‐OES) and mass spectrometry (MS). This new heterogeneous nanocatalyst showed the perfect catalytic activity towards synthesis of tetrahydrobenzo[b]pyran and Dihydropyrano[3,2‐c]chromenes derivatives through multicomponent reaction of dimedone or 4‐hydroxycoumarin, malononitrile and aromatic aldehydes in polyethylene glycol 400 (PEG‐400) at 100 °C. The influence of the amount of nanocatalyst, varying temperature of the reaction and the kind of solvent on the rate of condensation reaction was investigated. Recovery and reusability of the applied nanocatalyst was examined for five consecutive cycles without the significant loss of its catalytic activity.

A novel magnetic FSM-16 supported ionic liquid/Pd complex as a high performance and recyclable catalyst for the synthesis of pyrano[3,2-c]chromenes

“… 7 The main method for their preparation is the one-pot three-component reaction of 4-hydroxycoumarin with aldehyde and malononitrile in the presence of a catalyst. Consequently, a wide range of catalysts have been explored for the synthesis of pyrano[3,2- c ]coumarins, including t-ZrO 2 NPs, 8 SB-DABCO@eosin, 9 Fe 3 O 4 @GO-NH 2 , 10 chitosan-Zn, 11 l -proline, 12 rGO@Fe 3 O 4 @ZrCp 2 Cl, 13 and many others. However, many existing methods for the synthesis of these compounds exhibit limitations such as low yields of the product, relying on multi-step conditions, high reaction time, very expensive reagents, poor recovery of the catalyst, the use of toxic organic solvents, and a tedious work-up procedure.…”

Fe3O4@nano-almondshell/Si(CH2)3/2-(1-piperazinyl)ethylamine as an effective magnetite almond shell-based nanocatalyst for the synthesis of dihydropyrano[3,2-c]chromene and tetrahydrobenzo[b]pyran derivatives

“…Dihydropyrano[3,2- c ]chromene and tetrahydrobenzo[ b ]pyran are heterocyclic organic compounds containing oxygen and are very attractive. For this reason, so far, many catalysts including ZnO NPs 30 , t-ZrO 2 NPs 31 , SB-DABCO@eosin 32 , Fe 3 O 4 @GO-NH 2 33 , [PEMIM][OH] 34 , [(EMIM)Ac] 35 , L-Proline 36 , Chitosan-ZnO 37 , CESA 38 , Glycine 39 , rGO@Fe 3 O 4 @ZrCp 2 Cl 2 40 , Fe 3 O 4 @ G.tea /Cu 41 , etc. have been used for the synthesis of this class of compounds.…”