Pd-Catalyzed (3 + 2) Heterocycloadditions between
Alkylidenecyclopropanes and Carbonyls: Straightforward Assembly of
Highly Substituted Tetrahydrofurans
posted on 2020-06-29, 16:09authored byFelipe Verdugo, Eduardo da Concepción, Ricardo Rodiño, Martín Calvelo, José L. Mascareñas, Fernando López
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.