A highly efficient and simple procedure for the synthesis of 4H-benzo[b]pyrane derivatives is described. The reaction of 5,5-dimethylcyclohexane-1,3-dione or cyclohexane-1,3-dione with aromatic aldehydes and malononitrile using catalytic amount of alumina supported KF in reflux ethanol affords the title compounds in high to excellent yields and in short reaction times.