Photocatalytic-driven Three-Component Synthesis of 1,2,3,4-Tetrahydropyrimidine-5-carbonitrile Derivatives: A Comparative Study of Organocatalysts and Photocatalysts

The conversion of solar light into chemical energy using photocatalysts has become an important strategy to harvest solar energy. This green approach relies on using solar light to generate electron-hole pairs in photo-catalysts to initiate chemical reactions. Here, different 1,2,3,4-tetrahydropyrimidine-5-carbonitrile derivatives were obtained by utilizing TiO2 nanoparticles as photocatalysts and organocatalysts. The results indicate that, when TiO2 is employed as a photocatalyst in a clean solar system, it exhibits excellent performance in terms of yield and reaction time. Moreover, its photocatalytic behavior can be optimized by varying the photocatalyst amount and solvent system. In sum, the proposed method offers superior yield relative to the conventional thermal methods when exposed to solar radiation, whereby about 20 mg of TiO2 nanocatalyst is sufficient for the reaction completion. Moreover, the TiO2 nanocatalyst can be reused in up to four reaction cycles without activity or stability loss as confirmed by the characterization of pristine and recycled TiO2 photocatalysts using different analytical techniques.