Microwave-promoted sequential three-component synthesis of tetrahydrobenzo[b]pyran in water catlyzed by heterogeneous amine grafted on silica

A variety of tetrahydrobenzo[b]pyrans have been synthesized by sequential addition of arylaldehydes, cyanoacetate and then dimedone in water under microwave irradiation. A heterogeneous amine, N,N-diethylamino-propylated silica, was an effective catalyst for the reaction. The reaction with malononitrile provided the same result. The reaction condition was general to apply to the aldehyde having a Cl, NO2, OH, OMe, or CO2H group in satisfactory yield.