An Efficient One‐Pot Four‐Component Synthesis of Some New Spirooxindole Dihydropyridine Using Alum as a Heterogeneous Green Catalyst

4‐Nitro‐2,3‐dihydrospiroimidazo1,2‐a ]indeno2,1‐e ]pyridine‐5,3′‐indoline]‐2′,6(1H )‐dione derivatives have been synthesized in good yields in a one‐pot four‐component, and efficient process by reaction of corresponding isatins, 1,3‐indandione, diamine, and nitro ketene dithioacetal in the presence of KAl(SO₄)₂.12H₂O (Alum) as a nontoxic and easily available heterogeneous green catalyst.