Synthesis of benzo[b]pyran, 3,4 dihydropyrano[c]chromene and their new furan derivatives using Cu(II) complex of tetradentate Schiff-base supported on silica as a nanocatalyst

Cu(II) Complex of tetradentate Schiff-base supported on silica [Cu(II) Schiff-base@-SiO₂] catalyzed reactions of aryl aldehydes with carbonyl compounds (dimedon/4-hydroxy coumarin/1,3-cyclohexadion) and malononitrile in aqueous media (H₂O:EtOH) to preparation of benzo[b]pyrans and 3,4-dihydropyrano[c]chromanes. Also, using this nanocatalyst, 2-(5-substituted phenyl)furan-2-carboxaldehyde derivatives with carbonyl compounds (dimedon/4-hydroxy coumarin/1,3-cyclohexadion) and malononitrile gave novel tetrahydrobenzo[b]pyran and 3,4-dihydropyrano[c]chromane derivatives in high yields in H₂O:EtOH under reflux conditions. The key advantages of this catalytic systems are the formation of novel products, high yields (78%–93%), short reaction time, broad substrate scope, environmentally friendly reaction conditions and also, without need to column chromatography for purification. Furthermore, the nanocatalyst can be reused six times without losing catalytic activity.