Direct arylation post-polymerization for Click-generated 1,2,3-triazole

Abstract

Post-polymerization/functionalization approaches are promising tools for diversifying polymer synthesis. Herein, we report a combination of Cu-catalyzed azide–alkyne cycloaddition (CuAAC, Click reaction) and direct (C–H) arylation (DA) as post-polymerization strategies applied to the side chains of polystyrene. The Click reaction between azide-functionalized polystyrene (polymer 1) and an alkyne afforded a polystyrene derivative (2) bearing a 1,2,3-triazole moiety on its side chain. The triazole unit introduced via the Click reaction serves as a reactive site for subsequent C–H activation in the DA process. Post-polymerization of 2 with a bromoarene under optimized conditions enabled successful arylation, despite the generally low reactivity and selectivity associated with triazole C–H activation. Optimization was crucial to overcoming these challenges. The use of carboxylate ligands with bulky alkyl groups in the catalytic system significantly enhanced the reaction efficiency. The DA post-polymerization proceeded smoothly under a catalytic system composed of PdCl₂, K₂CO₃, and a bulky carboxylic acid additive (isostearic acid) in N,N-dimethylformamide (DMF) at 100 °C, affording the arylated product (3) in quantitative yield without side reactions that typically lead to polymer insolubilization. To further expand this approach, we applied the Click reaction to azide-terminated polystyrene, generating a polymer with a reactive 1,2,3-triazole end group. Subsequent DA with a bromoarene led to a dual-functionalized polymer end. This Click-induced, 1,2,3-triazole-based building block strategy demonstrates potential for polycondensation and post-polymerization of functional polymers.