A water–ethanol on–off fiber catalyst for the synthesis of substituted 2-amino-2-chromenes

Abstract

A DMAP (4-dimethylaminopyridine) functionalized polyacrylonitrile fiber catalyst (PAN_DMAPF) was prepared and used to efficiently catalyze three-component condensation reactions among an aldehyde, malononitrile and α-naphthol in water to afford the corresponding substituted 2-amino-2-chromenes. The PAN_DMAPF exhibited excellent catalytic activities in water and methanol, but failed to show any catalytic activity in ethanol and solvents with low polarity. In other words, water can turn the reaction on but ethanol shuts it off. This differs greatly from the same reaction catalyzed by free DMAP or by a tertiary amine functionalized polyacrylonitrile fiber. The PAN_DMAPF catalyst is applicable to a wide range of aromatic aldehydes (80–99%). Moreover, this newly developed fiber catalyst also exhibited excellent recyclability and reusability (up to seven times) without any additional treatment.