Succinimide-Based Ionic Liquids: An Efficient and Versatile Platform for Transformation of CO2 into Quinazoline-2,4(1H,3H)-diones under Mild and Solvent-Free Conditions

Multifunctional succinimide-based ionic liquids (SIILs) were well-designed and synthesized, and they were used as a dual solvent–catalyst for efficient transformation of CO2 and 2-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones under mild conditions. The catalytic behaviors, including the effects of anion–cation structures and reaction parameters, catalyst recyclability, and versatility were thoroughly studied. The optimum [HTMG][Suc] comprising a tetramethylguanidine cation and a succinimide anion showed excellent activity toward various substituted 2-aminobenzonitrile substrates. [HTMG][Suc] was easily recyclable with superior structural integrity. The possible pathways of CO2 and 2-aminobenzonitrile activated by [HTMG][Suc] were investigated in depth, which supported the reaction mechanism well. In comparison with reported catalysts, the protocol herein exhibited comparable catalytic performance under milder and greener conditions without any additional organic solvents.