Promoted synthesis of spirooxindoles in the presence of chitosan containing an acidic ionic liquid bridge in aqueous medium

Abstract

Chitosan (CS) containing an acidic ionic liquid bridge (CS-(M₃SP)₂-NH₂·HSO₄), was successfully prepared and utilized as a promoter in the one-pot multi-component synthesis of (±)-spiro[indoline-3,4′-pyrazolo[3,4-b]quinoline]dione and (±)-spiroindoline-pyrano[2,3-c]quinolone derivatives as important building blocks in pharmaceutical and medicinal chemistry. The catalytic efficiency was evaluated using a model reaction, and the yield was determined by HPLC analysis. This eco-friendly protocol offers several advantages, including low catalyst loading, excellent yields, short reaction times, and easy separation of the products. Notably, the catalyst was separated and reused several times without significant loss of its activity. In addition, the reaction was also investigated on a gram-scale, which showed that this method can be applied well at high amounts. In this study, the structural features and morphology of the catalyst were also thoroughly characterized using various techniques, including FT-IR, FESEM, EDX/EDX-map, XRD, TGA/DTG, and the Hammett test.