Efficient access to bicyclo[4.3.0]nonanes: Copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-tethered allenes

Article abstract of DOI:10.1002/anie.201508125

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. Three in one: Three consecutive chiral carbon centers are formed in one step by a copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-tethered allenes. Thus cis-hydrobenzofuran, cis-hydroindole, and cis-hydroindene frameworks are prepared with exceptional yields (80-98 %) and enantioselectivities (94-98 % ee).