Rapid and Solvent‐Free Synthesis of Sparingly Soluble π‐Conjugated Fluorophores by High‐Temperature Ball‐Milling Suzuki‐Miyaura Cross‐Coupling

Traditional Suzuki‐Miyaura cross‐coupling reactions are highly dependent on liquid organic solvents, which severely limits the use of poorly soluble substrates that are difficult to synthesize under standard solution‐phase conditions. To address this issue, we report an efficient, solvent‐free mechanochemical reaction for palladium‐catalyzed Suzuki‐Miyaura cross‐coupling reactions using high‐speed ball milling. This solid‐state synthetic method overcomes solubility limitations and demonstrates excellent functional group tolerance, including examples with steric hindrance and interactions that lead to decreased solubility. This synthetic method provides a practical, sustainable, and robust alternative route for constructing complex conjugated structures showing near‐infrared or blue fluorescence. The photophysical properties of the obtained molecules were measured to give the structure–property relationship. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) analyzes were conducted to provide the rational insights for physical properties.