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.
Rao et al. (Mon,) studied this question.