Propargylic cation-induced intermolecular electrophilic addition–semipinacol rearrangement

A novel propargylic electrophile-induced tandem intermolecular addition–semipinacol rearrangement was developed efficiently under mild conditions. Various allylic silylether substrates as well as Co-complexed propargylic species were applicable to this protocol and gave a series of synthetically useful β-propargyl spirocyclic ketones in moderate to good yields. Its synthetic application was also demonstrated by an efficient construction of the key tricyclic moiety of daphlongamine E.