New Aryl Derivatives of Quinolinedione and Related Heterocyclic Compounds

The synthesis of new derivatives of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione via palladium/Sphos-mediated Suzuki–Miyaura cross-coupling reaction is reported. The 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione intermediates were prepared in a three-step reaction from 8-hydroxyquinoline. The palladium-catalyzed reactions of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione with a variety of aryl boronic acids provide coupled compounds in high yields. The arylation of 6,7-dibromoquinoline-5,8-dione and 6,7-dichloroquinoline-5,8-dione with 4-bromophenyl boronic acid supplied 6,6′-(1,4-phenylene)bis(7-bromoquinoline-5,8-dione) and (4-(6-(4-(6-chloro-5,8-dihydroquinolin-7-yl)phenyl)-5,8-dihydroquinolin-7-yl)phenyl)boronic acid respectively, in addition to the expected coupled compounds in moderate yields. Also, Pd(0)/PPh₃ allowed the 7-chloro-6-(4-nitrophenyl)quinoline-5,8-dione and 7-chloro-6-phenylquinoline-5,8-dione to be synthesized via Heck reaction. The yields of the synthesized target molecules depend largely on the reaction conditions and the type of ligands employed. Structural assignments of the synthesized compounds were established by spectra and analytical data.