Direct Construction of Acid-Responsive Poly(indolone)s through Multicomponent Tandem Polymerizations

Multicomponent polymerizations (MCPs) as a burgeoning field in polymer chemistry has proved to be a powerful and popular tool for the synthesis of functional polymer materials with diverse and complex structures. To explore the general applicability of MCPs and enrich the product structures of MCPs, multicomponent tandem polymerizations (MCTPs) with great synthetic simplicity and efficiency were pursued. In this work, MCTPs of <i>N</i>-(2-iodophenyl)-3-phenyl-<i>N</i>-tosylpropiolamide, aromatic terminal alkynes, and diamines were explored through combining Sonogashira coupling and Michael addition reaction in a one-pot procedure. The MCTPs could proceed efficiently and conveniently under mild conditions with Pd(PPh₃)₂Cl₂, CuI, and <i>i</i>-Pr₂NEt, affording 12 poly(indolone)s with unique structures and high <i>M</i>_ws (up to 30400 g/mol) in high yields (up to 97%). The poly(indolone)s possess a unique acid-triggered fluorescence "turn-on" response which could realize specific detection of CF₃SO₃H from other inorganic and organic acids through a rapid acid-catalyzed reaction from enamine to ketone.