Deep eutectic solvents (DESs) as powerful and recyclable catalysts and solvents for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones

Abstract

Deep eutectic solvents (DESs) are successfully used as powerful and recyclable catalysts and solvents for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones (DHPMs). The acidity of DESs is the main factor that determines catalytic activity. DESs, based on p-toluene sulfonic acid (PTSA) and choline chloride (ChCl), exhibits the highest catalytic activity. ChCl/2PTSA is suitable for a vast variety of aromatic aldehydes with electron-donating and electron-withdrawing groups, different β-diketonates, and urea or thiourea to obtain the corresponding DHPMs. Furthermore, DESs can be recycled easily after synthesis. The reused DESs achieve catalytic efficiency six times without significant changes. This study will provide a new green catalyst and efficient process for the synthesis of DHPMs.