Miniaturised cross-coupling reactions: Solid dispensing approach for high-throughput screening

A solid dispensing method was developed for miniaturised high-throughput screening of Suzuki-Miyaura and Mizoroki-Heck carbon‑carbon (C[sbnd]C) cross-coupling reactions in a 96-well aluminium block. Silica (SiO₂) was used as an inert carrier for coating or physisorption of reagents (phosphine ligands and palladium catalyst). Volumetric scoops were used to dispense SiO₂ coated with reagents into the reaction without using an analytical balance. This new approach enables high-throughput experimentation (HTE) for screening reagents and/or catalysts as an alternative to the conventional method of preparing stock solutions. After screening 192 conditions, a combination of bases and phosphine ligands were identified as optimum reaction conditions. These include NaHCO₃, K₂CO₃, and Cs₂CO₃, and several phosphine ligands for the Mizoroki-Heck reaction, and Cs₂CO₃ and cyclohexyl diphenyl phosphine for the Suzuki-Miyaura reaction. This method enhances efficiency and precision in high-throughput catalysis.