Sulfated polyborate as an eco-compatible solid acid catalyst for efficient and facile solvent-free synthesis of polyhydroquinolines

An environmentally viable, green and efficient protocol for the synthesis of polyhydroquinolines using sulfated polyborate catalyst have been developed by Hantzsch four-component condensation between aromatic aldehydes, dimedone, ammonium acetate and ethylacetoacetate or ethylcyanoacetate at 100 °C under solvent-free condition. The sulfated polyborate catalyst is characterized by FT-IR, XRD, SEM and EDAX techniques. The noticeable features of this methodology are mild Brønsted acidic nature of the catalyst, good to excellent product yields (85–94%), short reaction time (18–30 min), solvent-free condition, operational simplicity and applicability to a wide range of substrates (29 examples). Graphic Abstract This work deals with sulfated polyborate catalysed green and efficient solvent-free synthesis of polyhydroquinolines.