Tuning the Chiral Environment of C₂-Symmetric Diene Ligands: Development of 3,7-Disubstituted Bicyclo[3.3.1]nona-2,6-dienes

Through the structural analysis of bicyclo[3.3.1]nona-2,6-dienes, new C(2)-symmetric chiral diene ligands 1 based on 3,7-disubstituted bicyclo[3.3.1]nona-2,6-diene framework have been designed and synthesized. These chiral ligands readily bind to rhodium(I) and provide a different chiral environment from the existing chiral dienes. The rhodium complexes thus obtained act as effective catalysts for 1,4-addition of alkenyl- and arylboronic acids to various alpha,beta-unsaturated ketones, including several combinations that were previously difficult to provide high enantioselectivity.