Sulfamic Acid Catalyzed One-Pot Three-Component Synthesis of Spiro-Oxindole Fused Dihydroquinazolinone Derivatives in Aqueous Medium

A simple, efficient, and straightforward protocol has been developed for the synthesis of spiro-oxindole fused dihydroquinazolinone derivatives from one-pot three-component reactions of isatoic anhydride, various primary anilines, and substituted isatins using a catalytic amount of sulfamic acid as an organocatalyst in water under refluxed conditions. All the synthesized compounds were formed within just 2 h and isolated pure by simple filtration with excellent yields (89%–94%). Gram scale production, use of commercially available low-cost organocatalyst, green solvent, reusability of the medium, one-pot three-component reaction strategy, no column chromatography, and high atom economy are some of the major benefits of this newly developed protocol.