One-pot synthesis of 3-hydroxy-2-oxindole-pyridine hybrids via Hantzsch ester formation, oxidative aromatization and sp3 C-H functionalization using FeWO4 nanoparticles as recyclable heterogeneous catalyst

Synthesis of poly-substituted 3-hydroxy-2-oxindole-pyridine hybrids is reported via sp(3) C-H bond functionalization as key steps using FeWO4 nanoparticles as reusable heterogeneous catalyst. Formation of Hantzsch ester (DHP) followed by aromatization, and sp(3) C-H bond functionalization was achieved using FeWO4 nanoparticles (20 mol%) at 80 degrees C. Temperature dependent reactivity was observed for mono aldol (at 80 degrees C) and bis aldol (at 120 degrees C) products. The catalyst was regenerated and reused up to 6 cycles without losing catalytic activity. The FeWO4 nanoparticles were also used for oxidative aromatization of different DHP derivatives and for the sp3 C-H functionalization of 2-methyl pyridine.