The new phthalic acid-based DES as a versatile catalyst for the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromenes

Abstract

Abstract Deep eutectic solvents (DESs) have found many applications in recent years and with countless advantages over regular solvents, not only complying with green chemistry principles but also acting as catalysts depending on their properties. In this regard, a new DES (MTPPBr-PHTH-DES) was prepared from a mixture (molar ratio 1:1) of methyltriphenylphosphonium bromide (MTPPBr) and phthalic acid (PHTH), characterized with various techniques such as FT-IR, TGA/DTA, densitometer, eutectic point, and 1H NMR and used as an acid catalyst in the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromes in solvent-free conditions. Short reaction time, high efficiency, and easy recycling and separation of the DES catalyst are among the most important features of the presented method.