The merger of vinyl-N-triftosylhydrazones and silver catalysis to enable stereoselective vinylcyclopropanation of alkenes

Despite extensive synthetic efforts, the application of vinyl-N-sulfonylhydrazones as a vinylcarbene precursor remains a persistent challenge in carbene chemistry, owing to the competitive formation of pyrazoles through [1,5] self-cyclization. Here, we report a strategy to address this long-term issue by combining vinyl-N-triftosylhydrazones and silver catalysis. This strategy inhibited the formation of pyrazoles and offered a highly electrophilic silver vinylcarbenoid species, thereby establishing a powerful silver-catalyzed stereoselective vinylcyclopropanation of alkenes. We found that diverse alkenes and vinyl-N-triftosylhydrazones are well suited for this protocol, affording a variety of vinylcyclopropanes in high yield with excellent stereoselectivity. The usefulness of this method was further showcased in gram-scale synthesis, late-stage modification, and total synthesis of bioactive molecules. DFT calculations disclosed that both the easy decomposition of vinyl-N-triftosylhydrazones and the weak coordination of silver play a crucial role during the vinylcyclopropanation of alkenes.