Data processing. We trained the models on reaction data recorded on a subset of the in-house ELNs covering compounds synthesized between 2004-2020. At the time of data extraction, there were 11,210 recorded Buchwald-Hartwig reaction variations with a yield greater or equal to 20%. A reaction variation is a recorded reaction with a specific set of conditions, whereas a reaction in the database only specifies the reactants and products. The arbitrary limit of 20% yield is a reasonable compromise between considering the reaction successful enough in a medicinal chemistry context and retaining enough data for modeling. For modeling, we reduced the dataset by only keeping reaction variations that use any of the 30 most common chemical contexts, giving 6,291 reactions.