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.