Facile ionic liquid-mediated, microwave assisted green synthesis, and antioxidant studies of novel indolin-2-one annulated spirochromanone conjugates

摘要

A convenient and efficient synthetic protocol of ionic liquid, 1-n-butyl-3-methylimidazolium tetrachloroferrate, [bmim]Cl center dot FeCl3 mediated synthesis of novel indolin-2-one annulated spirochromanone conjugates was described. These spirochromanone conjugates were efficiently synthesized by Kabbe condensation of substituted 3-[2-(5-acetyl-2,4-dihydroxyhenyl)-2-oxoethylidene]indolin-2-ones with various cycloalkanones catalyzed by pyrrolidine in ionic liquid [bmim]Cl center dot FeCl3 under microwave irradiation. This approach offers the advantages of short reaction time, mild reaction conditions, high yields, convenient operation, and reuse of ionic liquid. The synthesized compounds were evaluated for their antioxidant activity. Among the compounds synthesized, IVb and IVd exhibited the highest antioxidant activity. The IC50 values for compounds IVb and IVd were found to be 1.25 and 1.74 mu M, respectively, comparable to that of ascorbic acid (IC50 8.64 mu M), a standard antioxidant agent.