An expedient and straightforward solvent-free synthesis of 1,8-dioxo-octahydroxanthenes using eco-friendly aluminized polyborate catalyst

The present work deals with a catalytic application of aluminized polyborate as a mild solid acid catalyst for multicomponent synthesis of 1,8-dioxo-octahydroxanthenes under solvent-free condition at 100 degrees C-110 degrees C. It involves selective domino Knoevenagel-Michael reaction of 1 mole of aromatic aldehyde with 2 moles dimedone. The aluminized polyborate is simply synthesized by using boric acid and aluminum trichloride and characterized by FT-IR, XRD, SEM and EDAX techniques. The mild Lewis acidity, crystalline solid nature, stability and recyclability are significant features of the catalyst. The solvent-free condition, clean reaction profile, inexpensive and non-toxic catalyst, operational simplicity, good to excellent product yields, reduced reaction time and applicability to wide range of substrate are crucial features of this protocol.