Starting with an initial list of 115 solvents, the discrete variable space was first reduced based on several criteria (e.g., removal of inherently basic solvents such as pyridine given the reaction is acid catalysed) as given in Table . HE and Ir(ppy)3 catalyst solubilities were the most important criteria in selecting the candidate solvents. Even though suspensions can be pumped using the Vapourtec peristaltic pump, the presence of solids was found to block and scatter light. Therefore, solvents that can achieve clear solution in 40 mM reaction scale were selected based on the measured solubility values, with the full list provided in Table in the ESI. Five sigma moments were used for the parameterisation of solvents. Since each descriptor value and range are different, the descriptors were first standardised before implementing PCA.