Efficient synthesis of tetrahydrobenzo[b]pyrans under solvent-free conditions at room temperature

A range of tetrahydrobenzo[b]pyrans have been synthesized in very good yields under solvent-free conditions by grinding alpha-cyanocinnamonitrils or beta-cyano-beta-carbethoxy styrene and 5,5-dimethyl-1,3-cyclohexanedione in the presence of TEBA as catalyst. The short reaction time, cleaner reaction, and easy workup make this protocol practical and economically attractive.