The impurity reaction ranked first features an acetylation of just the aromatic hydroxyl group, although this can be questioned due to the I) the likely reduced concentrations of starting material after formation of main product and II) the lower nucleophilicity of alcohols relative to amines, shown by the reduced hits (830 against 12180 for 3). It is important to note that the workflow is designed such that all potential impurities are suggested without consideration of yields or concentrations of reacting species. Consideration of these factors would be challenging and require more data than is currently available in reaction databases.