Asymmetric synthesis of bicyclic pyran scaffolds bearing two oxa-quaternary stereocenters via zinc-catalyzed [5 + 1] annulations

Abstract

An enantioselective [5 + 1] annulation of α-hydroxyl aryl ketones with cyclohexadienone-tethered enones via chiral dinuclear zinc catalysts is reported. A Brønsted base and Lewis acid cooperative activation model is the critical factor for the chirality transfer process, giving access to a wide array of enantioenriched bicyclic pyrans scaffolds bearing two oxa-quaternary carbon centers with good yields and high optical purities. Notably, this reaction offers a new reaction mode of α-hydroxyl ketones as C,C-bisnucleophiles in catalytic asymmetric transformation.