One-Pot Multicomponent Solvent-Free Synthesis of 2-Amino-4H-benzo[b]pyrans Catalyzed by Per-6-amino-β-cyclodextrin

An efficient three-component reaction of aromatic aldehyde, 1,3-cyclohexanedione/dimedone, and malononitrile was developed, for the first time, using per-6-amino-beta-cyclodextrin, as a supramolecular host for aldehydes and an efficient base catalyst, which produced various substituted 2-amino-4H-benzo[b]pyrans in good to excellent yields, under solvent-free conditions. The catalyst can be reused at least three times without any marked change in its catalytic activity. Other remarkable features include a much milder procedure, a shorter reaction time, a wide range of functional group tolerance, and absence of any tedious workup or purification. This procedure also avoids hazardous reagents/solvents and is thus an eco-friendly alternative to the existing methods.