NiFe₂O₄ Nanoparticles: A Green and Reusable Heterogeneous Catalyst for the Synthesis of Spiro[indole-3,2′-Pyrrole]-2,5′(1H,1′H)-Diones

Abstract

The catalyst can be recovered magnetically and reused in five consecutive runs with only two percent decrease in yield.

Engaging Isatins in Multicomponent Reactions (MCRs) – Easy Access to Structural Diversity

“…The recycling of this magnetic heterogeneous catalyst was easily made by introducing a magnet stirrer bar to the reaction mixture in order to separate the catalyst. It was found that the product yields decreased to a small extent after each reuse of the catalyst, showing good recoverability [57] …”

“…NiFe 2 O 4 NPs [12] , [57] SnO 2 NPs [74] ZrO 2 NPs [98] NiO‐SiO 2 [125] NiO@g‐C 3 N 4 [126] ZnO nanodiscs [127] SrFe 12 O 19 MNPs [154] Cell‐CuI NPs [187]…”

Nickel‐Catalyzed Multicomponent Reactions: An Overview

“…Sharif and co‐workers demonstrated a heterogeneous nickel‐catalyzed synthesis of spiro[indole‐3,2’‐pyrrole]‐2,5’(1 H ,1 ’H )‐diones via a four‐component condensation protocol involving two molecules of substituted phenyl amines, isatins and acetylenedicarboxylates, which showed excellent yields using nickel ferrite nanoparticles in ethanol under reflux conditions [37] (Scheme 26). The methodology could sustain various functional groups (both electron‐donating and electron‐withdrawing) effectively.…”

Magnetically Separable Transition Metal Ferrites: Versatile Heterogeneous Nano‐Catalysts for the Synthesis of Diverse Bioactive Heterocycles

“…Well characterized magnetic nano‐NiFe 2 O 4 was employed as an efficient heterogeneous catalyst for the synthesis of spiro[indole‐3,2′‐pyrrole]‐2,5′(1 H ,1′ H )‐diones ( 51 ) by via one‐pot three‐component reactions of arylamines ( 2 ), acetylenedicarboxylates ( 49 ) and isatins ( 50 ) in ethanol under reflux conditions (Table ) . A wide variety of other metal catalysts such as ZnCl 2 , NiCl 2 , NiO, FeCl 3 , Fe 3 O 4 were tested in various reaction conditions and were unable to produce the desired product with satisfactory yields.…”