10.1016/S1872-2067(12)60693-7
The study focuses on the synthesis of 4H-pyran derivatives using a silica-bonded N-propylpiperazine sodium n-propionate (SBPPSP) as a recyclable catalyst. The catalyst was prepared from commercially available and inexpensive starting materials and was used to catalyze the synthesis of various 4H-pyran derivatives, including 3,4-dihydropyrano[c]chromenes, 2-amino-4H-pyrans, 1,4-dihydropyrano[2,3-c]pyrazoles, and 2-amino-4H-benzo[e]chromenes. The chemicals used in the study included aromatic aldehydes, malononitrile, dimedone, ethyl acetoacetate, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, and α-naphthol, which served as reactants in the multi-component reactions to form the desired 4H-pyran derivatives. The purpose of these chemicals was to participate in condensation reactions under refluxing aqueous ethanol conditions, with SBPPSP facilitating the process and being easily recoverable and reusable, highlighting the environmental and economic benefits of the method.