Dysprosium–balsalazide complex trapped between the functionalized halloysite and g‐C3N4: A novel heterogeneous catalyst for the synthesis of annulated chromenes in water

Abstract

In this work, a complex of dysprosium and balsalazide was trapped between the functionalized g‐C3N4 and halloysite via a simple approach. The resulting [Hal‐BS/g‐C3N4‐Dy]‐heterogenized complex was characterized using FT‐IR, SEM, EDX, elemental mapping, XRD, ICP‐OES, and TGA. The catalytic activity of [Hal‐BS/g‐C3N4‐Dy] was examined in the synthesis of an array of biologically active pyran derivatives, that is, the 2‐amino‐5,10‐dioxo‐4‐aryl‐5,10‐dihydro‐4H‐benzo[g]chromene‐3‐carbonitriles. This reaction was achieved in water as a green solvent under reflux condition. The desired products were obtained in excellent yields (up to 98%). In addition, the reusability of this novel catalyst was investigated for 8 cycles without losing catalytic activity and under the optimal reaction conditions. The ICP‐OES test demonstrated that there was no leaching of metal during the catalytic reaction, indicating the heterogeneous manner of the catalyst.