Immobilized piperazine on the surface of graphene oxide as a heterogeneous bifunctional acid–base catalyst for the multicomponent synthesis of 2-amino-3-cyano-4H-chromenes

Abstract

<p>A green method for the efficient synthesis of 2-amino-3-cyano-4<italic>H</italic>-chromenes using immobilized piperazine on the surface of graphene oxide (piperazine-GO) as a new heterogeneous bifunctional acid–base catalyst is developed.</p>

Effective removal of Pb(II) ions using piperazine-modified magnetic graphene oxide nanocomposite; optimization by response surface methodology

“…In the FT-IR spectrum of the Pip@MGO (Fig. 2 ), the stretching vibration of C-H bonds of the graphene oxide (GO) is apparent in the 2928 cm −1 46 . The hydroxyl groups and also carboxylic groups on the surface of the GO is obvious at 3443 cm −1 .…”

Tandem imine formation via auto-hydrogen transfer from alcohols to nitro compounds catalyzed by a nanomagnetically recyclable copper catalyst under solvent-free conditions

“…Cu-isatin Schiff base-γ-Fe 2 O 3 as a nanomagnetically heterogeneous catalyst was synthesized according to our previously reported method. 16 Cu-isatin Schiff base-γ-Fe 2 O 3 as a nanomagnetically heterogeneous catalyst, was synthesized by functionalization of γ-Fe 2 O 3 with 3-aminopropyltriethoxysilane and then the reaction with isatin to produce isatin Schiff base-γ-Fe 2 O 3 followed by the reaction with dissolving CuCl 2 ·2H 2 O in methanol ( Scheme 1 ).…”

“…In continuation of our efforts on the introduction of new heterogeneous catalysts for organic transformations, 16 we have recently synthesized Cu-isatin Schiff base-γ-Fe 2 O 3 ( Scheme 1 ) and used it as a new heterogeneous catalyst for the synthesis of bis(indolyl)methanes and bis(pyrazolyl)methanes. 17 Herein, in this paper, we have expanded the scope of application of this catalyst for the tandem imine formation by auto-hydrogen transfer from alcohols to nitro compounds under solvent-free conditions.…”

A novel base-metal multifunctional catalyst for the synthesis of 2-amino-3-cyano-4H-chromenes by a multicomponent tandem oxidation process

“…In our reported catalysts, we have profited from the presence of two nitrogen atoms in imidazole for the immobilization of imidazole onto a MNPs as a solid support on one side and then functionalization of supported imidazolium salts on the other side. Following our attempts for the developing multifunctional heterogeneous catalysts in organic reactions 68 – 70 , herein, we have tried to design a new base-metal multifunctional catalyst from supported imidazole onto MNPs for the generation of 2-amino-3-cyano-4 H -chromenes via a three-component TOP starting from alcohols. For this purpose, at first the free nitrogen of supported imidazole was functionalized with pyridine by the reaction with 3-(chloromethyl) pyridine hydrochloride and then the chloride anion in the resulting imidazolium ILs was exchanged with tungstate to produce (γ-Fe 2 O 3 -Im-Py) 2 WO 4 (Fig.…”