Efficient atom-economical solvent-free one-pot multicomponent synthesis of 2-amino-4H-benzo[b]pyrans catalyzed by solid base SiO2-OK as a reusable catalyst

An efficient one-pot, atom-economical, three-component reaction of aromatic aldehydes, dimedone, and malononitrile was developed, for the first time, using SiO2-OK as an efficient solid base reusable catalyst, producing various substituted 2-amino-4H-benzo[b]pyran derivatives in good to excellent yields, under solvent-free conditions at 80 A degrees C. This synthesis was confirmed to follow the group-assistant-purification chemistry process, which can avoid traditional chromatography and recrystallization purifications. The catalyst is inexpensive and easily obtained, stable and storable, and easily recycled, being reused at least six times without any marked change in its catalytic activity.