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

In the present work, derivatives of phenanthridine-6(5)-ones and benzo[]chromenes were efficiently prepared through an intramolecular C-H bond functionalization reaction catalyzed by photochemically synthesized Pd-PVP nanoparticles. The heterocycles were obtained intramolecular arylation of the corresponding -methyl--aryl-2-halobenzamide or aryl-(2-halo)benzyl ethers using KCO as base in a mixture of HO : 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, Bu, Ph, OCF, CF, F, Cl, -CN, Naph), and both bromine and iodine substrates showed great reactivity. Finally, the antiproliferative activity of phenanthridine-6(5)-ones and benzo[]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-benzo[]chromene was identified as the best compound with promising values of activity (GI range 3.9-8.6 μM). Thus, the benzochromene core was highlighted as a novel organic building block to prepare potential antitumor agents.