Iridium-Catalyzed Z-Selective Asymmetric Allylic Substitution Reaction via Z/E Kinetic Resolution

Chiral Z-olefin molecules are much more challenging targets in organic synthesis due to their thermodynamically unfavorable nature compared with that of their corresponding E-olefin counterparts. Particularly, the transformations toward advanced chiral Z-olefin products from readily available E-olefin precursors are faced with huge difficulties associated with the energetic uphill process. A possible solution to this issue is taking advantage of the different kinetic behaviors between Z- and E-olefins. However, recognizing the different reactivities between Z- and E-olefins poses great challenges for molecular catalysis. Herein, we report an Ir-catalyzed Z-selective asymmetric allylic substitution using oxindoles as nucleophiles via the kinetic resolution of Z/E olefin mixtures. The higher reactivity of Z-allylic carbonates than their E-counterparts in this reaction manifold originates from the faster oxidative addition of Z-allylic carbonates to the Ir(I) catalyst and the faster nucleophilic attack to anti-π-allyl-Ir intermediates than that to syn-π-allyl-Ir intermediates by external nucleophiles. When coupled with photoinduced olefin E/Z isomerization, the same products are accessed from E-allylic carbonates in up to 97% yield with 96% ee and >19:1 Z/E ratio. The results reported in this study represent an unprecedented pattern in asymmetric Tsuji-Trost-type reactions, a class of fundamental transformations in organic synthesis, and provide a unique approach to advanced chiral Z-olefins.