Synthesis of fluorescent multisubstituted polyquinolines by cascade C–H activation-based polyannulations of isonicotinamides and diynes

The development of new and efficient polymerization strategies for the synthesis of multisubstituted fused heterocyclic polymers with attractive properties is of great significance.Herein,a rhodium-catalyzed polyannulation route is developed for the in situ generation of multisubstituted polyquinolines with efficient aggregate-state fluorescence.Based on the cascade C-H activation of isonicotinamides and their annulations with internal diynes,a series of high molecular weight polyquinolines are efficiently produced in high yields of up to 99%in a facile and atom-economical manner.Unlike conventional two-component stepwise polymerizations,these polyannulation reactions are tolerant to monomer non-stoichiometric conditions and proceed even more thoroughly in the presence of an excess amount of the isonicotinamide monomer.Benefiting from the unique multisubstituted polyquinoline structures,the obtained polymers show high thermal and morphological stability,useful aggregation-induced emission(AIE)properties,and tunable aggregated-state fluorescence behaviors.The AIE-active polyquinoline is demonstrated to be a good lysosome-specific fluorescent probe with low cytotoxicity and excellent photostability.