Palladium nanoparticles for the synthesis of phenanthridinones and benzo[ c ]chromenes via C-H activation reaction.

In the present work, derivatives of phenanthridine-6(5 H )-ones and benzo[ c ]chromenes were efficiently prepared through an intramolecular C-H bond functionalization reaction catalyzed by photochemically synthesized Pd-PVP nanoparticles. The heterocycles were obtained via intramolecular arylation of the corresponding N -methyl- N -aryl-2-halobenzamide or aryl-(2-halo)benzyl ethers using K 2 CO 3 as base in a mixture of H 2 O : DMA as solvent without additives or ligands. High yields of the heterocyclic compounds were achieved (up to 95%) using a moderately low catalyst loading (1-5 mol%) under an air atmosphere at 100 °C. The reaction exhibited very good tolerance to diverse functional groups (OMe, Me, t Bu, Ph, OCF 3 , CF 3 , F, Cl, -CN, Naph), and both bromine and iodine substrates showed great reactivity. Finally, the in vitro antiproliferative activity of phenanthridine-6(5 H )-ones and benzo[ c ]chromenes was evaluated against six human solid tumor cell lines. The more active compounds exhibit activity in the low micromolar range. 1-Isopropyl-4-methyl-6 H -benzo[ c ]chromene was identified as the best compound with promising values of activity (GI 50 range 3.9-8.6 μM). Thus, the benzochromene core was highlighted as a novel organic building block to prepare potential antitumor agents.