Computational Mechanistic Studies. Once the quinuclidine and phosphinate fragments were determined as crucial for the success of the enantioselective reaction, catalyst-substrate complex structures were evaluated by docking the sulfonimidamide substrate in catalyst pockets proximate to the two groups. Choosing catalyst 3e as a model catalyst, we found that the quinuclidine nitrogen and the phosphinate oxygen atoms can act as hydrogen-bond acceptors (Figure ). The cinchona-phosphinate catalyst efficiently forms doubly hydrogenbound structures, anchoring the sulfonimidamide substrate (Figure ). During this binding event, we note that there does not seem to be any differentiation between imido versus amido nitrogen binding or preferential binding of one of the rapidly tautomerizing 1a enantiomers. We did, however, proceed with these structures as a starting point to evaluate the addition of 2,2,2-trifluoroethyl trifluoroacetate 2a. In light of our kinetic results, we extensively evaluated the direct addition of 2,2,2-trifluoroethyl trifluoroacetate 2a to benzenesulfonimidamide 1a, as well as the subsequent collapse of the tetrahedral intermediate 10aa as the possible turnover limiting steps. Both scenarios fit the experimental rate law and agree with catalyst active site control experiments; thus, it is challenging to rule out one scenario conclusively over the other based purely on empirical data.