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

Palladium-catalyzed cross-coupling of bicyclopropylidene (1) with iodoethene (11) in the presence of a secondary amine 12 provides allylidenecyclopropanes 13 which undergo immediate Diels–Alder reactions upon addition of dienophiles 14–18 to provide 8-(1′-aminoethyl)-substituted spiro[2.5]oct-7-ene derivatives 23a–26a 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 19–22 and N-phenyl-triazolinedione 37 to furnish highly substituted spiro[2.5]oct-4-enes and spirocyclopropanated heterobicycles 47a–49a, 41a–46a (17–50%). Spirocyclopropanated heterobicycles such as 55, 56 (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 53, 54.

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