A total of 103 DAAA reactions of α-aryl containing substrates were gathered from published work from within the Guiry group. Initially, we sought a very straightforward approach to featurization of both the substrate and the catalyst to maximize the subsequent human interpretability resulting from the ML outcomes based on our previous work. Each substrate was described using a common core structure broken down into the structural elements A-D (Scheme 2). To minimize the descriptors needed for featurization, the structural units B-D were approximated just by the van der Waals volume of each unit (as calculated by the method of Zhao ) and electronically by the Hammett parameter of the nearest published analogue. The latter being obtained from a wide-ranging review (e.g., methyl used for CH2, ethyl for CH2CH2, phenyl for the o-phenylenes). Our aim was to compare the utility of this bespoke explainable feature approach to both traditional molecular featurization methods (i.e. via RDKit), and GNN approaches (e.g. HCat-GNet). 21 Scheme 2. A-D fragment approach. For example, the left most structure in Scheme 1C is defined as containing the fragments: A = Ar, B = O, C = ortho-C6H4, D = CH2.