Sulfuric acid-modified PEG-6000 (PEG–OSO3H): a biodegradable, reusable solid acid catalyst for highly efficient and eco-friendly synthesis of novel bis-Knoevenagel products under solvent-free conditions

Sulfuric acid-modified PEG-6000 (PEG–OSO3H) is used as a highly efficient, biodegradable, and reusable acid catalyst for the synthesis of novel acyclic and heterocyclic bis-Knoevenagel products under thermal solvent-free conditions. The remarkable features of this green, new methodology are high conversions, cleaner reaction profile, simple experimental and work-up procedure, and economic viability. The catalyst is characterized for the first time by SEM-EDX and powder XRD. The catalyst can be reused several times without significant loss of its catalytic activity.