Electrophile Scope. The electrophile was also investigated using the optimized reaction conditions for 1a with catalyst 3e (Figure ). Variations of the leaving group (purple sphere) were investigated and compared to the model electrophile 2,2,2-trifluoroethyl trifluoroacetate 2a. Changing to the more electron-rich leaving group of ethyl trifluoroacetate 2b resulted in no conversion, which is presumably due to the poorer leaving propensity of this group. Consistent with this observation, the reactivity is reestablished upon incorporating a better leaving group, N-trifluoroacetoxy succinimide (2c); however, this reaction resulted in no selectivity. Interestingly, selectivity correlates with leaving group ability, wherein phenyl trifluoroacetate 2d and S-ethyl trifluoroethanethioate 2e demonstrate modest improvements in enantioselectivity. Additional electrophiles were also evaluated to explore the range of acyl groups that can be incorporated using this method (green sphere). Use of 2,2,2trifluoroethyl difluoroacetate 2f gave excellent selectivity (99:1 er) but with reduced conversion (48%) compared to 2a. More electron-rich electrophiles 2g, 2h, 2i, and 2j resulted in no conversion. Ultimately, 2,2,2-trifluoroethyl trifluoroacetate 2a was determined to be the optimal electrophile for this transformation.