Stereo-reversed E2 unlocks Z-selective C–H functionalization

The stereoselective functionalization of C–H bonds represents a central challenge in modern organic synthesis. Despite decades of innovation in C–H activation chemistry, methods for Z-selective functionalization of alkenes have eluded synthetic practitioners. Terminal alkenes present the biggest challenge for Z-selectivity as they require selective cleavage of the more hindered of two otherwise virtually identical C–H bonds. Herein, we describe the transformation of alkenes into transient 1,2-bis-sulfonium intermediates found to undergo Z-selective elimination, overturning a textbook E2 stereoselectivity rule through stabilizing interactions. We identify paired electrolysis as an enabling strategy to both selectively generate the requisite bis-sulfonium intermediate and drive its rapid elimination in situ. The resultant Z-alkenyl sulfonium linchpins provide access to a wide array of Z-alkene targets from inexpensive feedstocks through robust cross-coupling reactions.