Tetramethylguanidine-Functionalized Novel and Recyclable Nanocatalyst for the Synthesis of Pyrazolophthalazinediones

Abstract

The synthesis of pyrazolophthalazinediones has so far been carried out using acid, base, and ionic liquids catalysts, which in some cases are not easily recyclable, but in this work, three-component synthesis was carried out using a recyclable nanocatalyst. Therefore, a novel protocol was devised for the synthesis of pyrazolophthalazinediones by the reaction of phthalhydrazide, aryl aldehyde and 3-(1H-indol-3-yl)-3-oxopropanenitrile derivatives or malononitrile in ethanol and in the presence of newly synthesized Kit-6@HAp@Si(CH₂)₃-1,1,3,3-tetramethylguanidine (Kit-6@HAp@TMG) nanocatalyst with high to excellent yields (84–95%). The structure of the catalyst was determined using various analytical techniques, including FT-IR, XRD, SEM, EDX, Mapping, TEM, and TGA. The structures of the products were confirmed by spectroscopic analyses (¹³C NMR,¹H NMR, and FT-IR) and elemental analyses. The present method offers advantages, such as simplicity, high yields, and shorter reaction time, Easy method for separating the catalyst from the synthesized product, avoiding high temperatures and using low-risk solvents, atom economy, and catalyst recyclability up to four times without significant decrease in catalytic activity, which aligns with green chemistry principles.