One-pot, three-component, selective synthesis of the polyfunctionalized 4H-pyran and 4H-benzo[b]pyran derivatives in the presence of a highly efficient molecular sieve-supported zinc catalyst

A series of pentasubstituted 4H-pyrans and tetrahydrobenzo[b]pyrans are synthesized with excellent yields via a one-pot condensation of aromatic aldehydes, malononitrile, and a dicarbonyl compound, ethyl acetoacetate, acetyl-acetone or dimedone, in the presence of 4 angstrom molecular sieve modified with zinc(II) as heterogeneous catalyst, in ethanol. The process offers numerous advantages, such as better yield, short reaction time, and mild reaction conditions. The catalyst's preparation is simple and it could be reused while still maintaining its activity.