Solvent-free and green synthesis of fused pyrimidine derivatives catalyzed by pillar5arene-based Lewis acid ionic liquid

This study presents a solvent-free and green approach for the synthesis of novel 7,9-diaryl-6H,7H-chromeno4,3-dthiazolo3,2-apyrimidin-6-one (DCTP) derivatives using a newly developed pillar5 arene-based Lewis acid ionic liquid (P5/PyCuBr2Br) as catalyst. This catalytic system efficiently facilitates a one-pot, three-component reaction between 4-aminocoumarin, aromatic aldehydes, and 1-aryl-2-thiocyanatoethan-1-ones under solvent-free conditions. A wide range of DCTP derivatives were obtained in high to excellent yields (70–95%), demonstrating the tolerance of the catalyst for various functional groups. This protocol can also be used for the selective synthesis of mono-DCTP derivatives from dialdehydes. Key advantages of this methodology are excellent catalyst reusability over six runs without significant loss of its activity, high atom economy, low E-factor, and high turnover numbers (TON ~ 52–70), which are aligned with the principles of green chemistry. This work also highlights the significant potential of functionalized pillarnarenes in promoting sustainable and efficient multicomponent reactions for constructing complex fine heterocyclic scaffolds.