Cerium(III) immobilized on the functionalized halloysite as a highly efficient catalyst for aza-Diels–Alder reaction

Aza-Diels–Alder cycloaddition reaction is a critical synthetic method for the production of bioactive tetrahydroquinolines. To this aim, an imine obtained from the reaction of an aniline derivative and a carbonyl compound is cyclized with an alkene in the presence of a catalyst. In this research, some tetrahydroquinoline compounds are synthesized through aza-Diels–Alder reaction in the presence of a prepared Ce(III) immobilized on the functionalized halloysite (Ce/Hal-TCT-IDA) as a catalyst. Ce/Hal-TCT-IDA was prepared by incorporation of aminopropyl silane on the halloysite surface, followed by treatment with 2,4,6-trichloro-1,3,5-triazine (TCT) and iminodiacetic acid (IDA), and loading cerium nitrate. Then, it was characterized and analyzed by different analytical methods, indicating the amorphous agglomerated grains (20–60 nm), containing 0.00196 mmol g−1 Ce(III) ions. The catalytic activity and reusability of Ce/Hal-TCT-IDA were studied in this research.