The synthesis of disubstituted chiraldieneligands (3aR,6aR)- and (3aS,6aS)-10 with a pentalene backbone from the corresponding bicyclo[3.3.0]octa-1,4-diones 7 is described. The latter were accessible by enzymatic resolution of the racemic diol rac-5 and subsequent Swern oxidation. The efficiency of the ligands 10 in the rhodium-catalyzed1,4-addition of arylboronic acids 12 to cyclic and acyclic
highly enantioenriched cyclic β-aryl-substituted carbonyl compounds has been achieved through the RhI-catalyzed asymmetric1,4-addition of an array of arylboronicacids to cyclic α,β-unsaturated carbonyl compounds. In the presence of 0.1 or 0.5 mol-% of the RhI/1g complex, the products of conjugate addition were isolated in 89 to 98 % ee and in good to excellent yield.