N,N-Diphthalimide as Heterogeneous Recyclable Green Catalyst For Multi-component One-Pot Synthesis of 4-Aryl Substituted Dihydropyrimidinones Under Solvent-Free Conditions

The One-Pot multicomponent reaction (MCR) was an attractive broad area ofresearch in the synthesis of N-containing heterocyclic scaffolds such as the 3,4-dihydropyridin-2- 1H-(thiones) (DHPMs) and theirheterocyclic derivatives [1–3].Organocatalysts possess advantages such as cost-effectiveness, ready availability, a metal-freeenvironment, relatively low toxicity, simple functionality, non-sensitivity to airand moisture, promotion of a variety of chemical transformations via variousactivation modes, mildness of the reaction conditions required, huge potential forthe development of large-scale production of Biginelli reaction [3].In this work, N,N-Diphthalimide (DPHI) was directly synthesized via reaction of phthalicdianhidride with thiouera in solvent free. This reagent is found to be an efficient solid acidic organic catalyst in the Biginelli reaction. The three-component reaction of aryl aldehydes derivedthiourea, and ethyl acetoacetate or acetylacetone occurs by means of 10 mol % of (DPHI) insolvent-free reaction conditions. The present methodology is a green approach to access a series of 3,4-dihydropyrimidin-2(1H)- thiones in high yields. In addition, the use of DPHI as the catalyst offers several notable features such as simple operational procedure, no use of hazardous organic solvents, and recyclability of catalyst. (Figure 1).