Mechanochemical optimization and scope of triple and multiple Sonogashira couplings of triethynylbenzene for conjugated porous polymer synthesis

Conjugated porous polymers are an important class of advanced materials whose precise synthesis is critical for applications in energy storage, photocatalysis, and next-generation electronics. Developing greener routes remains challenging due to solvent-intensive, energy-consuming methods. Ball milling has emerged as a powerful and versatile tool in organic synthesis and materials chemistry, offering a sustainable and solvent-free alternative to traditional solution-phase methods. Here, we report the optimization of a triple Sonogashira cross-coupling reaction under room-temperature ball-milling conditions, achieving high yields in short reaction times of 60 min. The optimal catalytic conditions involved PdCl2(PPh3)2 and CuI as co-catalysts, triethylamine (TEA) organobase, and mechanochemical activation with low frequency (25 Hz) in air. The ball-milling coupling also proceeds with solid bases such as Cs2CO3 and under Pd-free or Cu-free variants, albeit with lower yields. Using triethynylbenzene as the core, ten derivatives incorporating electron-rich and electron-deficient aryl halides were synthesized, demonstrating scope and functional-group tolerance. The methodology extends to synthesis of CPPs, reporting three representative macromolecules comprising electron-neutral, rich, and deficient aromatics in high yields (71–89%). This mechanochemical approach enables a green, solvent-free, and operationally simple route to precisely structured advanced materials.