3-Amino-2-methylquinazolin-4-(3H)-one Schiff Bases Synthesis - A Green Chemistry Approach - A Comparison of Microwave and Ultrasound Promoted Synthesis with Mechanosynthesis

Green chemistry methods are important modern synthetic chemistry pathways with main advantages such as milder reaction conditions, shorter time, and higher yields. A series of quinazolinone based Schiff bases (1-27) have been successfully synthesized by using green synthetic methods, including microwave-assisted, ultrasound-assisted and mechanochemical synthesis, respectively. Desired compounds were prepared from 3-amino-2-methylquinazolin-4(3H)-one and substituted benzaldehydes with moderate to high yields (11-90%). Benzoxazinone and 3-amino-2- methylquinazolin-4(3H)-one, the precursors of Schiff bases, were prepared by microwave-induced synthesis. The structures of all Schiff bases are confirmed by ¹H and ¹³C NMR spectroscopy and mass spectrometry as well. A novelty of this research is the application and comparison of green chemistry methods in the synthesis of desired compounds which are listed above. The simplicity of synthesis includes ethanol as a solvent and no need for further purification.