Nanomagnetically modified thioglycolic acid (γ‐Fe₂O₃@SiO₂‐SCH₂CO₂H): Efficient and reusable green catalyst for the one‐pot domino synthesis of spiro[benzo[<i>a</i>]benzo[6,7]chromeno[2,3‐<i>c</i>]phenazine] and benzo[<i>a</i>]benzo[6,7]chromeno[2,3‐<i>c</i>]phenazines

Superparamagnetic nanoparticles of modified thioglycolic acid (γ‐Fe 2 O 3 @SiO 2 ‐SCH 2 CO 2 H) represent a new, efficient and green catalyst for the one‐pot synthesis of novel spiro[benzo[ a ]benzo[6,7]chromeno[2,3‐ c ]phenazine] derivatives via domino Knoevenagel–Michael–cyclization reaction of 2‐hydroxynaphthalene‐1,4‐dione, benzene‐1,2‐diamines, ninhydrin and isatin. This novel magnetic organocatalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least six times without significant loss in its activity. The catalyst was fully characterized using various techniques. This procedure was also applied successfully for the synthesis of benzo[ a ]benzo[6,7]chromeno[2,3‐ c ]phenazines.

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