Glycogen: A Novel Biopolymer Catalyst for the One-Pot Synthesis of Spirooxindoles, Spiro-Acenaphthylenes, and Spiro-2-Aminopyrans Derivatives under Mild Conditions

Background: Glycogen, a naturally occurring macromolecule, in its granular form and without any post-modification was found to be an efficient and eco-friendly bifunctional heterogeneous organocatalyst. This catalyst can be useful for the domino synthesis of various spiropyren annulated derivatives through three-component condensation of isathin, malononitrile, and diverse 1,3-dicarbonyl compounds, activated CH-acids, through Knoevenagel-Michael-annulation sequence under mild conditions. Corresponding spiro derivatives were obtained in high to excellent yields after 5-15 min stirring in 2 mL EtOH and 60°C in the presence of 0.01g of glycogen, equimolar amounts of isatin/ acenaphthoquinone/ninhydrin, malononitrile, and 1,3-dicarbonyl compounds. FTIR and 1H NMR spectroscopic showed there isn't any catalyst in the media and desired products were obtained in excellent purity. Avoiding any transition metal, one-pot, and multicomponent procedure catalyzed by a biopolymer, broad substrate scope, and operational simplicity are essential features of this methodology for the preparation of medicinally important compounds.