Step 5 is the pre-processing, cleaning and filtering the obtained analogue reactions. There are several potential issues with representing reactions extracted from Reaxys® , which have also been discussed in a recent review on transformation and structure data curation. Firstly, as is the case in Figure , invalid reactants, reagents and/or products may be present. These are species that have names but are either missing a SMILES representation and structure or contain an erroneous SMILES representation and structure when parsed by RDKit. In the case of the latter, valence errors are commonplace and in the case of the former, the species may be too complex or generic to identify an appropriate SMILES. These reactions are incomplete and are removed, together with reactions that are missing reactants and products. Additionally, analogue reactions may be missing all reaction conditions, which we define as encompassing reagents, solvents, catalysts, temperature, pressure, process (e.g. pyrolysis) and reaction time.