The aggregate data from the HTE screen also provided the opportunity to predict more selective monophosphines from the kraken library. To identify ligands for a highly (Z)-selective process, potential phosphines were initially filtered using the descriptor values that defined the reactive region of chemical space (Figure , orange box). Thereafter, the HTE selectivity data was employed to develop an ensemble of multivariable linear regression models that were used to virtually screen the remaining phosphines (see SI for details). Both P(4-ClC 6 H 4 ) 3 and PPh 2 (4-CO 2 HC 6 H 4 ) were predicted to be marginally more (Z)selective than L1 (Figure ). However, the ligands were found to be less reactive (presumably due to chemoselectivity issues) and slightly less selective than L1 upon experimental validation. Substrate Scope. With optimized conditions in hand, we sought to probe the efficiency and selectivity of both (E)-and (Z)-selective catalytic reaction regimes on a variety of different enol tosylates 1. To this end, ~50:50 mixtures of the enol tosylate diastereomers (E/Z)-1 were subjected to both optimized protocols (L1 in THF/H 2 O (4:1) (C1) or L2 in t-AmOH (C2)) with pinacol boronate 2a as the coupling partner (Scheme 1). Switching the conditions in such a way provided selective access to either diastereomeric tetrasubstituted alkene products (E)-and (Z)-3. In order to obtain potentially mechanistically relevant data from this substrate scope, the enol tosylate starting material 1 was geometrically divided into quadrants and stereoelectronically diverse substituents were explored for each. Generally, we were pleased to find that the desired ligand-modulated switch in diastereoselectivity was achieved for the examples evaluated. Thus, the diastereomeric product ratios typically ranged between 80:20-90:10 E/Z or Z/E, accordingly, with only minor exceptions. The same observation was made in terms of isolated combined yields of both product diastereomers, which were mostly between 70-90% and showed minimal dependence on the corresponding reaction conditions C1 versus C2. Notably, a substituent variation in the northwestern enol tosylate quadrant from ethyl (3a) to methyl (3b) and isopropyl (3c) led to a reduction in (Z)-diastereoselectivity from 86:14 (3aa) to 58:42 (for 3ba) and 68:32 Z/E (for 3ca). In contrast, there was no noticeable difference in selectivity or yield upon evaluating different substituents in the northeastern quadrant (products 3ea-3ha Importantly, the sterically encumbered cyclohexyl-substituted alkene product 3ea was accessed with the same switch in diastereoselectivity from 80:20 (using conditions C1) to 27:73 Z/E (using C2), indicating that our method is applicable to scaffolds that are not only derived from stilbene. The reduction in yield, especially for the (Z)-selective conditions, could be attributed to steric interactions with the bulky cyclohexyl group. Variation of para-substituents on the southwestern quadrant of 1 showed the subtle effect of electronic features on selectivity, in that a lower (E)-selectivity was observed for p-CF 3 (product 3la, 75:25 E/Z) than for p-OMe (3ka, 87:13 E/Z) while the (Z)-selectivity remained relatively consistent (3la, 89:11 Z/E and 84:16 Z/E for 3ka).