Easily accessible C2-symmetric chiral bicyclo[3.3.0] dienes as ligands for rhodium-catalyzed asymmetric 1,4-addition.

The synthesis of a new type of C(2)-symmetric chiral diene ligands with a nonbridged bicyclic [3.3.0] backbone was successfully introduced. Using highly efficient lipase-catalyzed transesterification and Suzuki-coupling strategies, a broad family of enantiopure 3,6-disubstituted bicyclo[3.3.0] dienes with different electronic and steric properties could be easily prepared. The application of these new diene ligands in the Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds have been examined, and excellent enantioselectivities (up to 98 % ee) as well as good yields are achieved under very mild reaction conditions at room temperature.