When higher sensitivity is desired, the NaBH4 concentration should be ³5 mM. Figure shows that when the NaBH4 concentration is above 10 mM, the reaction rates remain the same. DMSO and TFP concentrations. DMSO is an excellent solvent to dissolve APIs with a wide range of polarity and is convenient for the storage due to its low volatility and high stability. However, excess DMSO may be detrimental to the current method because DMSO can bind to palladium to form resting-state palladium species. Therefore, we hypothesized that tolerable DMSO concentrations might depend on TFP concentration. To determine the optimum concentration range for these two components, we titrated them in a combinatorial manner (Figure ) to find that 5-10% DMSO and 100-220 μM TFP were acceptable.