An efficient synthesis of N-substituted phthalimides using SiO₂-tpy-Nb as heterogeneous and reusable catalyst

A novel and efficient heterogeneous catalyst SiO₂-tpy-Nb was developed, and its application in the preparation of N-substituted phthalimides from o-phthalic acids or anhydrides with amines provides the desired products in good to excellent yields. The catalyst was stable and recoverable for eight consecutive cycles without a significant loss in its activity. Furthermore, the catalyst is applicable in continuous flow which indicates its potential utilization in industrialization.