Data-Driven Approach to Understanding Tetrabutylammonium Decatungstate-Catalyzed C(sp³)-H Functionalization...

Photocatalytic hydrogen atom transfer (HAT) has emerged as a powerful strategy for selective C(sp³)-C bond formation. Among these systems, photocatalyst tetrabutylammonium decatungstate (TBADT) has drawn attention for its ability to functionalize electron-rich C-H bonds via polar and steric control, often achieving highly regioselective outcomes. While these principles explain outcomes in simple scaffolds, translating them to understand regioselectivity in more complex molecules remains a central challenge. Here, we integrate electronic and steric descriptors to analyze the factors governing regioselectivity. The strong association of radical-based descriptors with observed selectivity trends motivates targeted mechanistic experiments to probe the extent to which catalyst-controlled hydrogen atom abstraction (HAA) versus radical-controlled addition governs regioselectivity. Deuterium-labeling studies reinforce that TBADT's HAA accessibility is broad across electronically similar C-H bonds. Kinetic analyses further establish that SOMO energy directly correlates with radical addition (RA) rates, showing that product distributions are funneled through frontier orbital control. Together, these results define the kinetic principles of radical sampling in TBADT-mediated functionalization, where HAA accessibility is broad, and RA kinetics further shape regioselective outcomes. Logistic regression analysis further demonstrates the value of mechanistically rich features in predicting site selectivity across complex molecular scaffolds.