Multicomponent Polymerizations of Isocyanides, Aldehydes, and 2-Aminopyridine toward Imidazo[1,2-<i>a</i>]pyridine-Containing Fused Heterocyclic Polymers

In the pursuit of advanced functional polymer materials, polymers with fused heterocycles have received tremendous attention owing to their unique photoelectric properties, good thermal properties, stimuli-responsive properties, and high refractive indices. However, their synthesis mainly relies on fused heterocycle-containing monomers and precursors, which has hindered the exploration of new polymer materials. Herein, transition-metal-catalyst-free multicomponent polymerizations (MCPs) of diisocyanides, dialdehydes, and 2-aminopyridine in ethanol were developed, which were featured with high efficiency and specificity, high atom economy, environmental benefits, and product structural diversity. The MCPs could not only generate long polymer chains but also build the fused heterocycle, imidazo[1,2-a]pyridine, from simple monomers, demonstrating great synthetic efficiency and simplicity. Six imidazo[1,2-a]pyridine-containing polymers with high molecular weights (Mw up to 41,700 g/mol) were obtained in high yields (up to 98%), which generally possessed good solubility, high thermal stability, unique fluorescence property, and acid/base-triggered reversible fluorescence switch behavior. The MCPs have provided an effective approach for the construction of functional polymers with complex structures, which may accelerate the development of fused heterocyclic polymer materials.