Efficient Access to Bicyclo[4.3.0]nonanes: Copper-Catalyzed Asymmetric Silylative Cyclization of Cyclohexadienone-Tethered Allenes

Abstract

The creation of three consecutive chiral carbon centers in one step is achieved using Cu-catalyzed asymmetric silylative cyclization of cyclohexadienone-tethered allenes. Through regioselective β-silylation of the allene and subsequent enantioselective 1,4-addition to cyclohexadienone, this tandem reaction could afford cis-hydrobenzofuran, cis-hydroindole, and cis-hydroindene frameworks with excellent yields (80-98%) and enantioselectivities (94-98% ee) bearing vinylsilane and enone substructures. Meanwhile, this mild transformation is generally compatible with a wide range of functional groups, which allows further conversion of the bicyclic products to bridged and tricyclic ring structures.

Keywords: allenes; asymmetric synthesis; copper; cyclization; silylation.