Amide/polyol deep eutectic solvents as green promoters for Suzuki coupling reactions

A strategy for enhancing organic chemical reactions was investigated using deep eutectic solvents (DESs). A DES system comprising caprolactam and sorbitol in a 3:1 molar ratio was developed and successfully applied to Suzuki coupling reactions. Under optimized conditions (100 °C, 25 min reaction time, 0.14 g/mol PdP 4 catalyst loading), the coupling of 12 bromoarenes with 7 phenylboronic acids was achieved, yielding products with > 71% conversion in all cases. Notably, the DES-catalyst system demonstrated the excellent recyclability, maintaining > 91% yield over five consecutive cycles. Through quantum chemical calculations, the hydrogen-bonding network within the DES and its coordination mechanism with PdCl₂ were elucidated. Comparative analysis revealed a 9.6-fold acceleration in reaction rate and an 80% reduction in catalyst consumption compared to the conventional methods. These findings established a green and efficient synthetic methodology for Suzuki coupling reactions, demonstrating significant potential for industrial-scale applications.