Dual Copper (II) Complex Supported on Diatomite as a Novel and Green Catalyst for the Synthesis of Dihydropyrano[3;2‐b]Chromenediones and Aminopyranopyrans

Abstract

Immobilized copper (II) complex, namely, 2,2'-((1E,1'E)-((6-(l2azaneyl)-1,3,5-triazine-2,4-diyl)bis(azaneylylidene))bis (methaneylylidene))diphenol, supported on diatomite (Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol) was introduced as a robust and heterogeneous catalyst for the synthesis of dihydropyrano[3;2-b]chromenediones and aminopyranopyrans. The Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol catalyst was synthesized by complexation of copper (II) acetate with TAT-Bis-(AZY-MY)Phenol as a ligand with oxygen and nitrogen ligation sites that were anchored on diatomite through 3chloropropyltrimethoxysilane. The prepared catalyst was characterized using different microscopic and spectroscopic techni-ques including SEM, TEM, EDX, XRD, FT-IR, TGA and ICP. The diatomite is available and cheap support with a high specific surface area and a large amount of hydroxyl group on the surface. A large amount of dual copper (II) complexes were supported on diatomite through covalent bonds. The Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol showed good catalytic activity for the synthesis of dihydropyrano[3;2-b] chromenediones and aminopyranopyrans using aromatic aldehyde, kojic acid, dimedone, or malononitrile. In addition, this catalyst system was reusable for five consecutive catalytic cycles without loss of their catalytic activity.