With this hypothesis in mind, we first obtained a library of literature examples of 6-endotrig radical cyclizations from Reaxys ® . Reactions were limited to sp 3 -centered radicals undergoing intramolecular cyclization onto a pendant olefin, resulting in a set of 99 reactions, which include a fairly even distribution of yields from 0 to 90%. For each reaction in the library, radical intermediates before and after cyclization were subjected to simple and rapid DFT calculations (uB3LYP/6-31g(d)) of physical descriptors . A total of 340 descriptors per reaction were extracted to constitute the input parameters, including molecular, atomic, steric descriptors and linear combinations (see SI for details). Next, the library was split into training and test datasets (70/30) by the Kennard-Stone sampling method . As a large number of descriptors (340) were used relative to the small library size (99), overfitting was a significant concern. Therefore, feature selection with correlation filtering and PCA dimension reduction were employed to transform 340 descriptors into 20 orthogonal parameters.