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A Pd catalyst made from a Pd(0) source and a bulky biaryl phosphine ligand promotes highly efficient intramolecular (3 + 2) heterocycloadditions between alkylidenecyclopropanes (ACPs) and carbonyls. The annulations provide a straightforward access to fused polycyclic systems featuring β-methylene tetrahydrofuran moieties. DFT data support a pallada–ene process and shed light on the critical role of hemilabile interactions between the Pd center and the bulky biaryl phosphine. Significantly, these Pd(0) catalysts are also effective for promoting intermolecular formal cycloadditions between ACPs and trifluoromethyl ketones, thus providing for a direct entry to chiral tetrahydrofuran moieties (THFs) bearing trifluoromethyl–substituted carbons.

Pyridine-substituted alkylidenecyclopropanes (Py-ACPs) react with gold(III) salts under mild reaction conditions through an unprecedented, proximal ring-opening pathway,to generate highly appealing,catalytically active pyridine alkenyl [C^N]-gold(III) species.M echanistic studies reveal that the activation of the C À Cbond of the ACPtakes place through an unusual concerted, s-bond metathesis type-process. Scheme 1. Top: Reported activation of ACPs with transition metals. Bottom:n ew reactivity profiles of pyridine-ACP derivatives with gold-(III) species.