A two-step four-component queuing cascade involving a Heck coupling, π-allylpalladium trapping and Diels–Alder reaction

Palladium-catalyzed cross-coupling of bicyclopropylidene () with iodoethene () in the presence of a secondary amine provides allylidenecyclopropanes which undergo immediate Diels–Alder reactions upon addition of dienophiles to provide 8-(1′-aminoethyl)-substituted spiro[2.5]oct-7-ene derivatives in 29–66% yield. The same one-pot, two-step queuing cascade can be carried out with other iodoalkenes including cyclic ones and with cyclic dienophiles such as N-arylmaleinamides and N-phenyl-triazolinedione to furnish highly substituted spiro[2.5]oct-4-enes and spirocyclopropanated heterobicycles , (17–50%). Spirocyclopropanated heterobicycles such as , (25 and 38% yield, respectively) can also be obtained by an inter-intra-intra-intermolecular version of this queuing cascade involving 1-hydroxyethyl- and 1-aminoethyl-substituted iodoethenes , .