Facile access to 1,2-disubstituted benzimidazoles and 2,3-dihydro-1H-perimidines using a biogenically synthesized single phase δ-MnO₂ NP catalyst and its dye removal study

A cost-effective and step-economic synthesis of pharmaceutically important 1,2-disubstituted benzimidazoles and 2,3-dihydro-1H-perimidine derivatives is accomplished without the assistance of external ligands. An environmentally friendly biogenic strategy for the synthesis of single phase δ-MnO₂ NPs using the Pongamia pinnata leaf extract was adopted. The phytochemicals detected in the extract of Pongamia pinnata leaves might be responsible for the reduction of Mn(vii) to Mn(iv), which provides stability to the metal centre. The synthesized catalyst was tested for the synthesis of pharmaceutically important benzimidazole and perimidine analogues. In addition, mechanistic experiments and the plausible mechanism were discussed. The δ-MnO₂ NP catalyst exhibited superior catalytic activity and high durability in the dye removal study.