Harnessing Palladium-Immobilized Magnetic Catalyst Nanoarchitectonics: Switching on Dual C–H Activation via Directed Arylation for Phenanthridinone Synthesis

A magnetically retrievable heterogeneous nanocomposite catalyst, Fe3O4@CPTMS-melamine-Pd, was developed by covalent anchoring of a Pd-immobilized melamine complex onto CPTMS-functionalized Fe3O4 nanoparticles. This nanoarchitectonics of the magnetic organic–inorganic hybrid composite serves as an efficient catalyst for direct dual C–H activation of N-methoxy benzamides with aryl iodides, enabling access to phenanthridinones via a one-pot intramolecular arylation strategy. Phenanthridinones constitute a pharmacologically important heterocyclic scaffold with prominent anticancer and anti-inflammatory activities, emphasizing the need for efficient and sustainable synthetic methodologies such as the one developed in this study. Comprehensive characterization by FT-IR, FE-SEM, EDX, elemental mapping, HR-TEM, XPS, and VSM confirmed the successful surface functionalization and structural integrity. The catalyst contains 2.65 wt % Pd (active catalytic site) and exhibits excellent magnetic retrievability and recyclability over five consecutive runs with minimal activity loss. The catalyst’s stability is further demonstrated by the retention of 2.56 wt % Pd, indicating minimal leaching. The engineered organic–inorganic hybrid composite demonstrates a clear structure–property–performance relationship, wherein robust surface functionalization preserves structural integrity, magnetic responsiveness enables facile recovery, and stable palladium immobilization minimizes metal leaching during catalytic operation. This work highlights a facile and recyclable strategy for efficient synthesis of a library of bioactive phenanthridinones (yields up to 90%) using a robust heterogeneous Pd catalytic system.