Sulfonated asphaltene as a highly efficient catalyst for the Mannich reaction with excellent diastereoselectivity and recyclability

This study investigates the repurposing of asphaltene, a petroleum waste product, as a catalyst for organic reactions. Sulfonated asphaltene was synthesized and evaluated for its efficacy in catalyzing the Mannich reaction, displaying notable diastereoselectivity and operating effectively under mild conditions. Characterization of the catalyst's chemical composition, structure, and thermal stability was conducted using FT-IR, TGA, XRD, CHN, BET-BJH, SEM, and EDS analyses. Employing the sulfonated asphaltene catalyst in a one-pot multi-component reaction to generate β-amino carbonyl derivatives in ethanol resulted in high product yields after 4-7 h. Notably, the catalyst exhibited recyclability, demonstrating reusability for at least 10 reaction cycles.