Copper Acetylacetonate–Immobilized Halloysite Nanotube: An Efficient Natural and Green Catalyst for the Synthesis of 4<i>H</i>‐Chromenes at Room Temperature

ABSTRACT A new copper acetylacetonate immobilized on halloysite nanotube (HNT) was synthesized. For this purpose, (3‐aminopropyl)trimethoxysilane (AMPTSi) was covalently bonded to the surface of halloysite nanotubes, and then copper acetylacetonate was immobilized onto the modified support. The chemical and physical structure of Cu(acac) 2 /AMPTSi/HNTs were characterized via various analyses such as TEM, SEM, EDS, FTIR, XRD, TGA, and N 2 adsorption–desorption. The efficiency of this catalyst was studied in a one‐pot three‐component reaction of benzaldehydes, dimedone, and malononitrile/ethyl cyanoacetate for the synthesis of 4 H ‐chromenes. For all substrates, good to excellent yields of the corresponding 4 H ‐chromenes were obtained.