The first step towards the design of a broader chemical space around the benchmarking dataset consisted of converting the geometries in the pericyclic subset of BH9 into SMILES, using the functionalities of RDKit. 30 Subsequently, reactive cores, i.e., collections of atom pairs undergoing a change in bonding throughout the reaction, were selected. Only those cores with a repeated occurrence, and for which a high σ in the DFT computed activation energies across functionals is obtained (a cutoff of 4.80 kcal/mol was set), were selected.