Background: 4H-benzo[b]pyran derivatives have attracted great interest
due to biological and pharmacological properties including antimicrobial, antiviral,
antiproliferative, sex pheromone, antitumor, cancer therapy, central nervous system
activity and other interesting biological activities. For these reasons several synthetic
methods are reported. For our part we want to propose an efficient procedure which
respects the environment.
Method: To achieve our study we performed a one-pot three-component reaction of
aromatic aldehydes, dimedone, malononitrile and pyridinium p-toluenesulfonate as
catalyst under different conditions.
Results: We found that the optimal conditions for the preparation of 2-amino-4H-benzo[b]pyrans catalyzed
by p-toluenesulfonate pyridinium are in refluxed water and with 10 mol% of catalyst. Given these
results and to show the generality of the procedure, we applied the optimized reaction conditions for the
synthesis of various 2-amino-4H-benzo[b]pyrans from a range of substituted aromatic and heteroaromatic
aldehydes. The desired products are obtained in good to excellent yields.
Conclusion: We have synthesized a variety of 4H-benzo[b]pyran derivatives according to a three component
reaction between aromatic aldehydes, dimedone and malononitrile using pyridinium
p-toluenesulfonate as a catalyst. This method gives very good yields and has the merit of simplicity, respect
for the environment by using water as solvent and an available and inexpensive catalyst.